Notes on KAP

This text was prepared as a method assessment I did for English Heritage (now known as Historic England) in 2009. Since then I have updated it from time to time as developments occur and knowledge expands.  I post it here in a web format as part of David Wheeler’s effort to pull practitioner knowledge together for How to KAP.com.

The audience for the original would have been a manager who wanted to know if commissioning a KAP shoot would be worthwhile. These days, if they are commissioning anything,  I think they’d just go for a drone…

All the images from the pdf are resized to 640px wide for webspeed. Text in red has been added as it occurs to me during the web recompile. If you have already read through the pdf version here then scanning the red text will make sense. Much of this will be familiar to readers of this blog and for that I apologise: there is a to-ing and fro-ing of ideas between what I post here and what gets added to the pdf KAP guide, like David I have bursts of activity where I try to consolidate information followed by long lulls of disappointment as I realise there are as many ways of doing this as there are folk doing it! By and large this is what works for me, I have tried, tested, broken, fixed and tried again most of what is written below.

I N T R O D U C T I O N

This guide is prepared as an introduction to the acquisition of photography using a kite to raise the camera. It is in 3 parts:

1.Application

2.Equipment

3.Procedure

It is prepared with the help and guidance from the world wide KAP community who have been generous with their expertise and support.

Blending a love of landscape and joy in the flight of a kite, KAP reveals rich detail and captures the human scale missed by other (higher) aerial platforms. It requires patience, ingenuity and determination in equal measure but above all a desire to capture the unique viewpoint achieved by the intersection of wind, light and time. Every flight has the potential to surprise us with views of a familiar world seen anew.

Mostly this is something that is done for the love of kite flying: camera positioning is difficult and flight conditions are unpredictable. If predictable aerial imagery is required and kite flying is not your thing then other UAV methods are recommended: if you are not happy flying a kite this is not for you. If you have not flown a kite then give it a go without a camera and see how you feel about it: kite flying at its best is a curious mix of exhilaration, spiritual empathy with the environment and relaxation of mind and body brought about by concentration of the mind on a single object in the landscape.

A C K N O W L E D G E M E N T S

The Author would like to particularly thank Christophe Gaston for sharing his knowledge with me and he in turn he relays a debt of gratitude to Christian Becot.

I have made use of the thoughtful and diligent material posted online by

Brooks Lefler, Charles Benton, Simon Harbord, Pierre Lesage, Harald Prinzler, David Hunt, Peter Bults, Ralf Beutnagel, David Mitchell, and the generous help of all at KAPiNed 2010.

I have been greatly assisted by Clive Hollins (d.2013) in the adaptation of radio equipment for KAP and I am indebted to his expert knowledge.

Thanks to Steve Cole for comment on the photographic aspects of the text.

Acronyms and abbreviations used in this guide:
AGL
Above Ground Level
Absolute datum is rarely used for the height of kites (or aircraft).
AuRiCo
Automatic Rig Control
System of programmable stepped movements of the rig in 2 axes for near 360 sweeps of the camera.
AutoKAP
Automatic Kite Aerial Photography
Light weight passive system of controlling the camera.
Bft.
Beaufort wind scale number
Useful to describe the range of wind speeds experienced.
CAA
Civil Aviation Authority
To whom we must apply to fly higher than 60m
CCD
Charged Coupled Device
The light sensor which records the image in a digital camera.
CHDK
Canon ‘Hack’ Development Kit
Enables a script to be used to programme the shutter interval on Canon cameras.
Deg.
Degrees
DSLR
Digital Single Lens Reflex camera
The standard to which camera resolution is compared for KAP. I expect someone has flown a medium format camera but I can’t see it becoming common practice.
EXIF
Exchangeable Image File Format
Metadata tags (describing exposure settings, camera identity date and time) embedded in a digital image file.
Ff30
Flowform kite of 30 foot square sail area
Steve Suttons patented kite is often referred to as the ff30, ff16 or ff8 depending on size.
FPV
First person view
A radio linked video camera used to relay the view form a remotely controlled aircraft, a virtual’ pilots eye’ view.
ISO/ASA
Film sensitivity measure used to describe CCD sensitivity level.
KAP
Kite Aerial Photography
NATS
National Air Traffic Service
NOTAM
Notice to Airmen
If you intend to fly above 200’ (60m) and permission is granted the CAA will post a NOTAM for a fixed period.
PAP
Pole Aerial Photography
A KAP rig is eminently suitable for using on the end of a pole.
PBL
Planetary Boundary Layer
The layer of the atmosphere we live in.
RC
Radio Control
Often used to mean remote control too.
Rx
Receiver
Radio amateur short hand
Tx Transmitter
UAV/UAS
Unmanned Aerial Vehicle/System
Remote controlled aircraft, autonomous mini-copter, dirigible balloon etc.

A P L I C A T I O N

Baconsthorpe x640

Baconsthorpe Castle , Norfolk. Oblique 3 image montage from a single centre at 60m AGL

History: a brief overview*

In May 1888 Arthur Batut (1846-1918) took the first of 2 photos which, in August of that year, he sent to Gaston Tissander and demonstrated that he had solved the 2 problems of balancing the weight of a camera with the lift from a kite and remote control of it by taking aerial photographs of Labruguiere, Tarn, France. In so doing he took the first known kite aerial photographs and for this and his subsequent development of the technique he is known as the father of kite aerial photography.

Batut 1888

The bridge over the river at Labruguiere, Tarn, France taken in March 1889 from a kite by Arthur Batut. His kite line is clearly visible at the bottom left.

He built a lightweight camera using a 9×12 cm glass plate negative. The camera was attached to the wooden frame of a diamond-shaped kite (which he had bowed for stability) and was triggered by a burning fuse.

By 1890, Batut had published the first book on kite aerial photography entitled La photographie arienne par cerf-volant–Aerial photography by kite. In the same year Batut was joined in the enterprise by Emile Wenz, and they developed a close working relationship that lasted many years. They quickly gave up the technique of attaching the camera directly to the kite frame in favour of suspension from the bridle below the kite. In this way, the camera could be brought down and reset while the kite remained flying. (This is very close to usual modern practice where the camera is suspended from the flying line rather than the kite itself).

The 19th century quest for the ‘conquest of the air’, beginning with George Caley in 1804 and with key advances (among many) by Otto Lilienthal (man lifter1889) and Lawrence Hargrave (box kite 1893), pushed kite technology to ever greater efficiency making kite borne cameras a practicality. The activities of Batut and Wenz in France gained worldwide press attention, and in 1895 kite aerial photographs were taken in the United States by William A. Eddy and Gilbert Totten Woglom.

F B Powell KAP 1897

B F S Baden Powell’s KAP image of Middleton Hall taken sometime before 1890. 

In Britain the development of flight saw kites kept in the public eye by personalities like Capt. B F S Baden Powell, who took successful kite photographs and S F Cody, both demonstrating man-lifting by kite.

Eddy 1895 x640

View from a kite-sustained camera suspended above American Tract Society Building. New York, by William A. Eddy c1895.  Image from: http://robroy.dyndns.info/KAP-history/photo_miniature/aerial_photography.html

By1906 the kite became the aerial platform of choice for George R. Lawrence who lofted a huge 0.6×1.2m panoramic camera of his own design 600m by a train of 17 kites to record San Francisco after the earthquake and fire of 1905 with tremendous resolution that is rarely surpassed even today.

San Fran 1906George R. Lawrence’s epic KAP panorama of the ruins of San Fransisco in 1906.

The field was rich with innovative apparatus and experimental techniques. The burning fuse was replaced by mechanical or electrical triggers. Improved cameras, multiple-camera rigs, and ingenious suspension systems were tested and patented. In 1912, Pierre L. Picavet (pronounced ‘pickavay’) invented a cable-and-pulley system for suspending the camera below the kite line.

Batut’s first images from a simple diamond kite began the development of a practice which continues to this day, new synthetic materials, radio control and digital photography make image capture from a kite ever more practical.  In placing a camera in the air by means of a kite we take a step along the journey of discovery began by Arthur Batut!

*Text adapted from ‘KAP History’ by James S. Aber with additional research by Christian Becot.

http://www.geospectra.net/kite/history/history.htm  and http://becot.info/aerophoto/anglais/&specialities.htm

KAP Applications

Kites are light, portable, and easy to launch, and their only power requirement is a steady wind. They can soar at altitudes too high or in winds too strong for tethered balloons, and they can be flown at levels so low that aircraft would be impracticable or unsafe. They also can be sent up quickly with little support equipment, so they can be used almost anywhere: from desert basins to Antarctic ice, from Peruvian rain forests to U.S. corn fields.

The flight endurance of a kite can exceed many powered UAVs by hours and thus generate a great deal of imagery. KAP is a means of providing low altitude photography, this means typically 30-60m above ground level (AGL) and, with appropriate permissions, ( Appendix 1) 120-200m can be achieved comfortably.

Kite flying needs an open space in which to launch and fly the kite. The nature of the kite is such that the zone of operation is a critical constraint on its use as a platform for photography: there are many places which are simply not accessible to KAP. Although skilled flyers can make the best of what wind and space they find choosing KAP as a method for a given subject is a choice best left to the kite flyer and it must be accepted other means may be needed to raise the camera in some cases.

KAP can be used for:

  •  Low level visitor orientation shots of monuments and sites
  • Condition recording, particularly of roofs, wall caps and vegetation coverings
  • Feature highlighting e.g earthworks and crop marks
  • Pattern imagery, particularly of human scale details
  • Habitat recording
  • Panoramic photography
  • Archaeological recording of excavations and post excavation condition recording
  • Characterisation studies
  • Planning assessment general views
  • Producing interesting images from an unusual viewpoint

The principal constraints on conducting photography from a kite are the required height of the image and the wind direction needed to get the best coverage. There are many cases where kite flying is simply not possible:

  • Under or near electricity transmission wires
  • In urban areas without open space for a launch site or space for a downwind line zone
  • Where access to open land is not granted
  • On or near highways, electrified railways and the transition zone of operational airfields
  • On days without wind ( less than Beaufort 2)
  • On days with stormy weather (greater than Beaufort5)

With careful planning and preparation KAP can provide useful imagery of a wide variety of sites, often capturing key images from a unique viewpoint.

Resource Availability

KAP requires 3 key skills:

  • Kite flying experience with a load lifting kite
  • Control systems knowledge
  • Photographic knowledge

It also requires specialist equipment maintained in good working order. Although basic KAP operations using ‘off the shelf’ kit are possible, getting predictable coverage via a remote view system requires maintaining integration of 2 radio systems on a minimum weight budget as well as competence with the flight of kites in a range of wind-speeds. KAP operators with flight experience of a range of kites should be competent to deliver imagery based on a sound assessment of flying conditions and make the right choice of equipment to match the flying opportunity. Kite flying conditions can be very local and KAP fliers need to be familiar with site conditions. The best results come from repeated efforts building on an understanding of local conditions. KAP works best with unobstructed ground upwind of the subject as kite flying in constricted, built-up areas is difficult.

Grimes x640Grimes Graves Neolithic flint mine, Norfolk. Low level oblique image showing human and animal trackways.

KAP for fun is very rewarding; it is the progression from simply getting a shot from the sky to getting directed photography that marks out serious KAP capability. Site evaluation, weather monitoring and preparedness for flight repetition are characteristics of a flier with a photographic agenda.

As a skill KAP requires an interdependency of equipment and knowledge, a kite is not like other photographic mounts such as a tripod or mast; it demands judgement on when to use it and practice in handling it in a variety of conditions before the operator can be confident about outcomes.

P H O T O  C O V E R

The ‘cone’ of capture:

A kite will place the camera downwind of the flier, this is obvious but it is the most important factor in planning photocover by KAP, the objective is to place the camera over the subject. It is possible to use height and shoot into the wind but there are 2 problems with this, first there will be a high percentage of shots with the flying line in view and second the camera will recede from the subject as it gains height.

The ideal is for the Sun to be at right angles to wind direction or from behind the flier; shots taken into the sun can be dramatic but often result in poor exposure.

Nadir coverage

Vertical imagery has the poorest coverage; the maximum 60m of available height offers a very small field of view compared to aircraft acquired imagery. KAP vertical coverage is of a very small area, consequently getting a predictable path and overlap is extremely difficult: it can be compared to trying to drop peas in to a thimble from a table top. The difficulty of maintaining a consistent photo-scale is almost insurmountable due to the variable flying height. The field of view can be increased by using a wide angle lens however there is a trade off between the increase in field of view and image distortion.

The zone of operation

The near ground space required for the flying line can be considerable. Obstructions in this zone such as trees, power cables, telegraph lines and buildings are a serious hazard for the kite. In a steady wind with a stable kite the zone of operation can be very narrow and the kite line can be threaded around obstructions once it is settled at a good height.

In variable winds the kite may need a broad sweep of sky and the clear zone needed becomes deeper and wider accordingly; the kite flier can become ‘pinned’ to the only spot where the kite will let him stand and photography will be restricted accordingly.

Moving the camera

The camera is moved around the sky in 2 ways: by walking the anchor point (the flier walks the kite) and the natural variation in airflow shifting the kite. Aiming the camera is achieved by remote control of pan, tilt and shutter; a video preview down link improves the process but many fliers work by judgement alone. If the nadir point is known (by an assistant observer) the camera can be moved by walking the kite to the appropriate point and then tracking to left or right, the natural tendency is to move downwind. Walking the kite upwind will temporarily raise it and it should be allowed to settle before shooting.

Wind ‘stagger’

The kite (and the camera) will rise and fall according to wind speed, it will also increase its distance from the flier as the speed drops, this means that classic parallel swath capture is not easily achievable from a kite, particularly if the flying height is restricted to 60m. The shift between one shot and the next can be beneficial as it can produce a good offset for stereo but it is problematic in getting consistency of swath cover.

Wind stagger x640

‘Wind stagger’ variation in cone of capture. As the wind-speed rises, so does the kite. This increases the field of view and reduces the down wind distance from the flier. Sequential imagery taken from the rising and falling kite will be subject to big shifts in scale and perspective centre.

Camera direction and Sun position

Pointing the camera at the Sun will generally produce poor imagery. On occasion it is possible to capture great shadow effects when the Sun is low in the sky by shooting against the light but ideally the sun is best placed at right angles to the direction of shot or behind the camera. A predictable direction of illumination is for the Sun to be behind the flier or to fly with the ‘wind out of the Sun’

Directed Camera or Auto?

The choice of capture strategy can often depend on how ‘comfortable’ the KAP environment is. An ‘uncomfortable’ environment might be a busy urban park. It’s reasonable to expect all manner of hazards to present themselves: running dogs, children, low flying objects like balls or frisbees, cyclists and horse riders can all appear without warning so an AutoKAP technique would allow the flier to keep both eyes on the kite and rig as well as a third over the shoulder! A classic directed camera application is a request to shoot a given subject or a situation where timing would require the camera to be aimed and shot at an anticipated moment.

AutoKAP

Fixed nadir rig

The simplest form of AutoKAP is to capture imagery on a fixed camera orientation and achieve coverage by walking the camera across the area to be mapped, the flier will need to anticipate the offset between the kite and the camera and estimate the coverage achieved relative to the rate of movement. A very simple rig can be used for this and the results can be most effective.  Photomaps based on simple nadir rigs can be achieved either as un-scaled mosaics or as metric ‘otrhophotos’ if sufficient control is available. Marking control points in sufficient density for KAP coverage is a considerable undertaking and derived control from existing mapping should be considered as an alternative to pre-marking the site.

Automated Pan and tilt stepping

AutoKAP is a method of moving the camera in fixed steps by robotic control, there are 2 variants: Pan only and pan and tilt, an intervalometer is used to take shots at a fixed time interval, say every 5s. The basic set up steps the pan axis in 30 deg steps. The advantage of the technique is that the flier can capture imagery without taking any action to control the camera, thus making the operation relatively easy for one person to operate. Capture simply requires the kite to be kept ‘on the spot’ for the time it takes for a 360 sweep and them moved on to a new centre.

AutoKAP image pattern X640

AutoKAP image swath. The 30 deg pan step generates a series of fan arrayed shots. The consistency of the coverage is dependant on the stability of the airflow; this diagram shows the effect of typical shifts in height superimposed on a single centre of rotation. In practice the centre will shift in plan between shots also. The imagery is of variable scale with multiple perspective centres and consequently very difficult to mosaic! Using a fixed nadir rig with an intervalometer will improve the image condition for photo-mapping.

Oblique fans

Basic pan step AutoKAP generates oblique fan imagery which has a consistent lack of parallelism. Registration of multi perspective centres is difficult as each image has a rotation of perspective centre relative to the next.

Bartlow x640

Tumuli at Bartlow, Cambridgeshire.  Shooting into the light can be dramatic but shadow areas will lose detail. Camera at 55m AGL.

NOTE ON CAMERA SETTINGS

It’s all too easy to rely on ‘Auto’ and for many cameras this will probably work well most of the time. Things start to go awry in low light, the Auto setting will generally assume a longer shutter speed is needed and the effect will be to increase the number of shots wrecked by motion blur. It is tempting to up the shutter speed but this will have the effect of under exposing in low light.

“When I’m launching close to sunset, I usually try to set the camera in aperture priority mode with exposure compensation to -2/3 ( to avoid blown highlights under contrasty conditions), and the ISO as high as I find acceptable. I feel that setting the aperture fairly wide open and allowing the shutter speed to vary is much better than setting a fixed shutter speed and severely underexposing many images. I have learned the hard way when setting the shutter speed at 1/500th or 1/1000th at the start of a KAP session with diminishing light.

Berkeley M Layefsky x640With my dSLR, I’ll usually set the camera to f/3.5 (the largest aperture on my kit lens) or f/4 with an ISO of 400. If I think I’ll continue flying after the sun sets, I’ll often set the ISO to 800.

On my Canon S90, I try not to go above ISO 100, despite its larger sensor and reportedly better performance at higher ISOs. I’m so used to the dSLR’s image quality at higher ISOs that even at ISO 200, I don’t like what I see with respect to noise from the S90. Printed images may not look as bad as on my monitor, I really should try a print test.

Even though my EXIF data shows manual exposure on the UC Berkeley sunset image (right) I was in aperture priority mode at f/2.5 (largest aperture on this camera is f/2, but I figure stopping down a little might keep things sharper on the edges and in the corners), with ISO 80. At 10 minutes before sunset the camera chose a shutter speed of 1/200th under these conditions. It definitely would be nice to feel good about ISO 200 (or 400) with the S90, which would have decreased the shutter speed more than 2 (or 4) fold, so I really will have to do some print tests.”

 Michael Layefsky August 2010

Boxgrove1 X640

Boxgrove2 X640
Boxgrove Priory Sussex. Low level oblique image recording hidden cill and lead capping condition.
Warham Camp x640
Iron-age hill fort at Warham Norfolk. Photomap montage of 9 images selected from 1,296 acquired over a 2.5 hours continuous capture flight.Nadir Imagery collected from 35 to 60m AGL. Overcast lighting has eliminated shadow allowing near continuous surface coverage. Vegetation condition and visitor erosion tracks are clearly visible. Some evidence of the earlier course of the River Stiffkey is revealed.
Dish x640
Radio Astronomy Installation at Haslingfield, Cambridgeshire. Details of One Mile Array reflector from 40m AGL

E Q U I P M E N T

The essentials are

C A M E R A

R I G  and its suspension and controls

K I T E  flying line and harness

C  A  M  E  R  A

Aerial photography traditionally uses very highest quality cameras and KAP is no exception in its demands on image resolution.

H Welcome 1913

Henry Welcome’s KAP rig and traveller at the excavation of Jabel Moy, Sudan in 1913 photo copyright Welcome Foundation.

To choose a camera to fly there are two considerations: image quality and weight. KAP works best in the lightest winds possible, strong winds are turbulent and place every part of the system under stress, including the flier! Light winds have their own problems but things will happen gently and the stability of the camera will be greater despite the frustrations of slow launches and poor flying angle. So the camera needs to be lightweight with the best resolution possible, by placing the camera in the air, details you are familiar with on the ground will appear much smaller than you expect and push the resolving power of the lens to the limit.

Power: You will not be able to turn the camera off whilst it is in the air, so setting up your camera to save the maximum amount of power is desirable and carrying spare batteries is a must.

Format: a compact camera will be lightest but will lack the image capturing performance (or resolution) of a DSLR due to its smaller sensor and the optical qualities of its lens. The DSLR might offer better optics, more instantaneous image capture and a larger sensor but will add considerable weight to the rig and will restrict the number flying days achievable as the higher wind speeds needed to lift it tend to be turbulent and increase the risk of damage during ‘heavy landings’ accordingly. The ‘micro four thirds’ format offers some of the benefits of the DSLR (large CCD, interchangeable lenses etc) and some of the compact (light weight, small size) formats and so it is well suited to KAP.

Desirable features for a KAP camera in addition to good resolution and light weight are:

  • standard ‘hot shoe’ for fitting a shutter servo
  • video relay of the preview screen
  • thread for a polarising filter or lens adaptor
  • tripod fixing thread  for mounting the camera securely to the rig

Lens:

Focal length: Common usage in describing lenses refers to focal length of the 35mm film format ‘prime’ sizes:

  • 50mm ‘Normal or ‘Standard’ lens with: angle of view of about 50° considered to have similar magnification and field of view properties to the human eye
  • 28mmm or less ‘Wide-angle’ lens with an angle of view wider than 60°
  • 100mm or more ‘Telephoto’ lens or long-focus lens, a much reduced field of view:

‘Zoom’ lenses are constructed to have the properties of an adjustable focal length from ‘wide’ to ‘telephoto’ (sometimes called ‘tele/wide’) they have advantages in flexibility but disadvantages in aperture, light loss and weight. For KAP wide angle lenses seem appropriate because, at the expense of some aberration around the edge of the image, it’s easy to frame the subject in the wider field of view.

A selection of commonly used ’pro compact’ cameras used for KAP, in descending order of weight per sensor area:

Camera Weight Key feature

Sensor size

mm

Sensor area/ weight.

mm2 per g

Canon G11
335g
10mp programmable
7.60 x 5.70
0.12
Ricoh ‘Calipo’    GX200
238g
12mp
7.60 x 5.70
0.18
Panasonic Lumix DMC-LX3/ LeicaDlux4
228g
Leica Wide Angle lens. Image stabilisation
8.17 x 6.13
0.21
HD GoPro 3 76g
14mp ‘super wide’ video camera

5.76 x 4.29

0.325

Panasonic DMC GF1
485g*
Interchangeable lenses. Micro 4/3rds format. ‘On lens’ stabilization
18 x 13.5
0.5
Olympus EP1 406g*
Interchangeable lenses. Micro 4/3rds format. ‘On board’ image stabilisation. 2/3rds full frame CCD.
18 x 13.5
0.598
Olympus E-PL1 368g*
18 x 13.5
0.66
Fuji X-E1 430g
16 mp ‘X-Trans’ CMOS Sensor. 14mm wide angle c.80g
23.6 x15.6
0.85
Ricoh GXR ‘S10’ or ’P10’
397g
12Mp. with 50mm ‘A12’ lens Interchangeable lens/sensor packs available.

23.6 x 15.7mm

0.903

Samsung NX200 305g*
21Mp, Samsung EX-S30NB 30mm f/2.0  Pancake Lens =85g
23.5 x 15.7mm
1.002
Sigma DP1/DP2
278g
14mp
20.7 x 13.8 mm
1.027
Leica M9
825g
Full frame, 585g body. (+240g  for 50mm Summicron f/2 lens)
36 x 24 mm
1.047
Leica X2
345g
16Mp Fixed 35mm equivalent focal length lens.
23.6x 15.8mm
1.08
Sony Nex 5
317g*
Interchangeable lenses. Sony ‘E’ mount. 14mp
23.4 x 15.6 mm
1.12
Leica X1
286g
12mp. Fixed 35mm equivalent focal length lens.
23.5 x 15.7 mm
1.29
*includes lightweight wide angle ‘pancake’ lens
Table updated 4.11.2012

Micro 4/3rds format

Compact cameras with a sensor of 18 x 13.5mm (or 4/3rds of an inch diagonal, ‘micro 4/3rds’ refers to the miniature lens mount standard adopted for compact cameras using the 4/3rds sensor) are light, have a good sized sensor and selectable lenses. The lighter models are ideal for KAP.

Full Frame format

Full frame format refers to equivalence to the 35mm film frame size. Full frame sensors are bigger than those used in most ‘compact’ cameras. The large sensor size produces better image quality but usually at the cost of using a heavy DSLR camera. The Leica M9 is exceptionally light for a full frame camera as its ‘range-finder’ design saves the weight of the mirror and prism used in classic SLR designs. The Sony RX 1 at 498g is the first lightweight mirrorless compact camera with a ‘full frame’ sensor. As of October 2013 Sony have announced a swappable lens mirrorless (digital reflex?) model A7 with an A7R version weighing 475 g without lens.

Shutter actuation and memory delay:

Some cameras can take a long time to process the image information from the sensor before the next shot can be taken. This is a particular problem on some compact cameras that use a large sensor array. The Sigma DP1 can take 4s to complete its auto-focus sequence and a further 12s to write the image file off the sensor onto the memory card. This is a problem resulting in poor framing when photographing from a moving platform like a kite.  Using such a camera will require patience!

NOTES ON CAMERA PERFORMANCE

The resolution of the camera is a function both the design and component quality (particularly of the optical chain) of the camera and the photographer’s choice of exposure settings. There are 3 key factors to consider:

1. Optical resolving power of the lens and the optical path design.

The transmission of focussed light rays to the sensor is the critical thing. This is fixed by the camera and lens design with bigger lenses and bigger internal focussing distances tending to give better resolution. There are good miniature cameras but if you want to print images at exhibition resolution all comparisons begin with the DSLR design. Small compact cameras use very small sensors to record the image which means that the performance of each component in the sensor is optimised for miniaturisation. The pixel count on these small arrays is increasing as the technology develops but the noise associated with these miniature arrays is a problem. The balance between these factors can end up with good image quality at wide apertures and slow shutter speeds or conversely a low pixel count but good exposure response.

 2. Sensor performance

Effective performance of the sensor and its associated processor is a function of the density of sensor elements, how close together they are and the sensitivity and overall size of the array, how many sensor elements (often, but not always, pixels) there are, together with the image processing algorithms used all affect the quality of the captured image.  Selecting a high sensitivity (high ISO settings) introduces noise into the image and degrades the quality.

3. Exposure

Most lenses have an optimum aperture of about f8 (usually about two stops down from the widest aperture). The shutter speed will be determined more by the need to arrest motion blur more than anything else. Exposure is a compromise between shutter speed, aperture and ISO setting. The brightness of objects on the ground is something of a surprise so care should be taken not to over-expose with too wide a stop as detail in the highlights will be lost. A high shutter speed will reduce motion blur at the cost of forcing wider aperture settings or higher (noisier) ISO settings. An EV (exposure value) setting of -1/3rd helps reduce ‘burn out’ of white or bright objects in bright light.

Camera settings for best resolution

Sharpness from foreground to background, known as ‘depth of field’ is a function of the aperture used, the focal length of the lens and the distance between the lens and the subject. As mentioned above noise introduced by high ISO settings will also affect the quality of the image.

A good mix in strong light for most cameras is:

Aperture=f 8

Sensitivity or ISO= 400

Shutter Speed=1/125ths

A polarising filter which deals with reflections and glare is useful as the high viewpoint will capture a great deal of reflected light from unforeseen sources. When the polarising filter is used the aperture will need to be wider by 2 full stops at f 4.8 or 6)

Photo scale (vertical (nadir) case)

S = f / H

Where S = scale of the photograph, f = focal length of the camera (in metres) and H = height of the camera (in m).

If you need to know what the ground cover for a given camera at a given height will be the photoscale formula will do this for a true nadir shot of a level surface. Photoscale=f/h where f= focal length of the lens  and  h= the height above the ground Because we want to know the ground cover rather than the photoscale we can use the ratio upside down to ‘scale up’ the sensor size to match the flying height: Ground cover = Sensor size x (h/f) Some typical KAP cameras give these values:

Theoretical NADIR ground cover at 60 and 100m AGL
 

a

b

f

h

(h/f x a) x (h/f x b)

Camera

Sensor x

Sensor y

Focal length

At a height of

Area on ground

Sony RX 1

35.8mm

23.8mm

35mm

60m

61m x 40m

 

 

 

 

100m

102m x 68m

Ricoh GR

23.7

15.7

18.3

60m

77m x 51m

 

 

 

 

100m

129m x 85m

Canon S100

7.6

5.7

6*

60m

76m x 57m

 

 

 

 

100m

126m x 95m

HD GoPro 3

5.76

4.49

2.77

60m

124m x 97m

 

 

 

 

100m

207m x162m

Canon Eos M

22.3

14.9

22

60m

60m x 40m

       

100m

162m x 108m

*widest setting on ‘tele/wide’ control

Of course ‘real world’ results will vary as flying heights are rarely consistent and introducing camera tilts changes the aspect of photocover hugely. These values do not take into account variations in ground height or image resolution.

Although photoscale can be applied to scaling from photography it is not recommended as it is a purely theoretical value.  The ratio only applies to a truly orthoganal projection of an image free of lens distortion and tilts in the image plane (a particularly severe problem as KAP gives very small h and f  values compared to classic air survey values) as these have a significant effect on the accuracy of the scale ratio across the image area.

Stability (anti shake) settings

If the camera has anti-shake control this should be used as it will be subject to vibration.

C O M P A R A T I V E   R E S O L O U T I O N

CanonIxus vs SigmaDP1x640TheLeft image is taken with the Canon Ixus 70 and the Right the by the Sigma DP1. The Canon is unmodified at focal length of 17.4mm and the Sigma fitted with a Ricoh DW-6 .79x converter which works out at something like 28mm equivalent.  Despite the much smaller CCD size and lower pixel count on the Canon the image is sharper.

The lower quality of the Sigma image is likely to be a product of the optical quality of the adaptor and the algorithms used to process the image after capture.

In looking for a KAP camera it is desirable to have the best mix of weight, lens, focal length and pixel count, however good lighting will improve the performance of any camera.

R I G

The rig has to perform 4 functions:

  • Stable support,
  • pan,
  • tilt and
  • fire the camera shutter,

additionally it may be used to transmit an image preview to the ground. For some, the rig is an all consuming passion; there is always a refinement in weight, miniaturisation, material or control to be made! If you build one you are solving some nice engineering problems with a balance between weight and rigidity as constraints. The requirement is to be able to pan, tilt and trigger the camera remotely whilst it is safely suspended from the kite line. Fortunately good rigs can be bought ‘off the shelf’ made by Brooxes at the excellent KAPShop www.kapshop.com. The rig needs to be rigid, lightweight and equipped with radio control with a good range and power life as, unlike other RC users; the kite may fly for hours so the transmitter and receiver need a high capacity power supply.

GPS X1 rig_x640Brooxes Radio controlled rig. My rig in 2013. 2.4GHz Spektrum RC with 5.8GHz video by Immersion RC Ltd. The suspension has been modified to take a pendulum.

Rig construction:

Weight vs. rigidity

Ideally the rig should have no more mass than that needed to support the camera and its control devices: it should not be designed to with stand a crash impact as its mass would exceed the available lift of most kites.  It is inevitable the rig will take some knocks and have to withstand transport to and from the flying field; a careful balance between strength and weight must be achieved.

 Suspension system Picavet vs. Pendulum:

Pendulum is heavy but gives a very stable and predictable camera position, there is very little backlash and stabilisation is very quick if a semi-rigid joint is used.

Pendulum x640I have discovered the pivot bar works well if cut in half and the length of the pendulum is not too critical and can be shortened for ease of handling. A minature horn cleat ( supplied for boat pennants) provides a much safer purchase for the flying line attachment:

Mk4 flight readyThe Picavet is light but much more mobile in higher wind speeds: ideally one would use a Picavet in light winds and a pendulum in higher, in practice it is not easy to swap over suspension systems so kappers tend to opt for one or the other. A disadvantage of the Picavet is it can be a headache to untangle if it goes wrong-keep the lacing diagram handy and keep a check on the pulley wear on the suspension lines. A big advantage of the Picavet is it packs away nice and small whereas a pendulum and bar is a bit bulky.

Picavet 4

Picavet lacing diagram. There are plenty on the web this one is by R Joe Brandon.

I use a picavet on my lightest rig as an option if the wind is too soft to lift anything else. There are 2 things to check carefully (assuming it’s not in a tangle)

  • The knot on the loop- it’s easy to forget it- it can work loose.
  • Wear on the picavet line as it passes through the eyes on the cross- Scott Armitage pointed out the Picavet relies in FRICTION to dampen movement and that friction induces WEAR on the suspension line.

Radio Control:

Note. Since writing 2.4GHz has become a ‘standard’  system for radio control models of all kinds. The digital pairing used eliminates cross channel conflicts and the video relay frequencey has moved to 5.8GHz for compatability.The cross frequecy interference described below is solved by adoption of a 2.4GHz system with a 5.8 GHz video link.The only downside is that the extra power drawn by the higher frequency video transmitter shortens the rig battery life and requires a UBEC voltage regulator to be fitted.

Radio control is used for the remote control of pan, tilt and shutter, this is not the only method of achieving camera movements as an automated series of shots can be made using AutoKAP (see AutoKAP at the end of this section).

In the UK and Europe (Region 1) there is a legally binding agreement that the 40 MHz  band is reserved for ground based radio controlled models and 35 MHz for airborne. There are several widely used suppliers of standardised components and choosing an RC brand is an important consideration because of the compatibility of connectors, voltages etc. tends to be brand dependant. It is desirable to be able to replace components quickly and easily as a KAP rig will demand more of the servos in terms of shock loading and torque than a model aircraft. RC modellers use systems which have been developed for over 50 years so making use of a model aircraft set comprising matched transmitter, receiver and 3 servos is a good way to begin.

Using a kite mounted receiver and three compatible servos, the pan, tilt and shutter can be controlled by joystick controls on the hand held transmitter.

Image preview:

The main problem with operating the camera remotely is that it is very difficult to tell what the camera is pointing at: even with binoculars.  The orientation of the camera is largely unknown unless the camera view can be seen on the ground.  To overcome this problem a low powered (10mW is the unlicensed limit for video) video transmitter is installed on the rig so that the image seen by the camera is transmitted to a portable receiver on the ground. There are a number of licence free channels in the 2.4GHz band making it is possible to mount a specialised lightweight TV transmitter on the kite rig and operate it from the same battery used by the control receiver and servos. Voltage conditioning equipment may necessary as often the video camera supply is incompatible with the control receiver supply.

FPV or ‘first person view’ flying is the new hobby of flying a model airplane through a wireless video camera as the availability of lightweight miniature video cameras has allowed operation of radio control model aircraft by using a ground viewable ‘pilots eye’ video link. KAP can use much of the same technology but has to overcome the interference problems caused by the proximity of the RC receiver and the video transmitter.

 Multiple radio installation:

In a model aircraft the RC receive antenna and video transmit antenna can be easily separated either by the fuselage length or the wingspan. This is not the case with a kite mounted setup. On a kite mounted camera the rig is compact and therefore any transmitting antenna is bound to be physically close to the RC receiving antenna and associated wiring to the servos. The orientation, screening and separation of the antenna for RC control and video link requires careful design to avoid the ‘deafening’ of the RC receiver by the video transmitter. The effect is to cause the rig controls to become unstable at distance from the RC transmitter so the control signal is ‘swamped’ by the video transmitter and the receiver sends garbled servo control signals to the servos resulting in uncontrollable ‘jitter’ of the rig movements.

This swamping is analogous to trying to hold a conversation with someone listening to heavy metal on their iPod. Even though the T.V. transmitter signal is far removed in frequency from the 35 MHz control signals, the receiver does not clearly ‘hear’ the messages being sent to it resulting in the servos behaving erratically.

There are several mechanisms whereby interference is presented to the receiver and therefore several methods of minimizing the interference problem.

  1. Separate the antennae as far as possible to opposite sides of the rig.
  2. Mount the antennae mutually at right angles and with opposing polarities for example one vertically and the other horizontally.
  3. Use a high specification ‘dual conversion’ type receiver.
  4. Screen the r/c receiver to minimise direct 2.4 GHz radiation into the set.
  5. Fit a filter on the antenna input to the r/c receiver to block 2.4 GHz but allow the 35 MHz signal through.
  6. Fit Radio Frequency bypass filters to the appropriate signal and/or power lines in the rig.

Ground reception of video link

As the 2.4 GHz transmitter has a 10mW restriction on the output power (See Appendix 3), it is necessary to either use a directional antenna on the receiver, or to obtain a license to use a higher powered transmitter on the camera rig. Several designs of gain antennas can be employed; however a patch antenna on the receiver boosts reception adequately. Although bulkier than a standard omni-directional antenna, a patch antenna is light in weight and can be worn by the kite flier easily in a neck bag, and can co-exist with the receiver.

 Tx x640

Ground equipment for radio control of rig.
  1. 35MHz radio control transmitter.  The tilt (up/down) and shutter (push and release to L or R depending on servo) are on the LH stick and the pan on the right.
  2.  2.4GHz video reciever. The antenna is demountable for transport and field survival. self powered with 8 selectable channels. (Fitted in camera operators neck bag for field use)
  3.  Patch antenna. Custom made which increases the signal strength from the video relay (Fitted in camera operators neck bag for field use)
  4. 2.5″ TV screen.self powered with clip strap to fix to RC controller. Supplied as a test monitor for CCTV installation.
Airside box x640R C Rig field case:
  1. Camera:10.2 Megapixel
  2. Camera:12.3 Megapixel
  3. Video transmitter with altimeter relay
  4. Shutter servo hot shoe mount
  5. x2Polarising filters
  6. Camera batteryV
  7. ideo link cable x2
  8. Split pins
  9. RC transmitter aerial (de-mounted)Lens cloths
  10. Lens cloth
  11. Rubber bands for mounting video Tx and RC aerial
  12. Charging tail
  13. 6v battery
  14. Gyro stabilised Tilt servo
  15. Pan gear
  16. Pan servo
  17. Pendulum mounting post
  18. RC aerial mounting clips

AutoKAP

AutoKAP is the term used to describe passive, automated image capture from a kite. It has the key benefits of

      • Light weight, low power rig
      • High volume of images captured
      • Simple operation
      • Kite flier relaxation!
      • Good base material for panoramic treatments captured.

It has the disadvantages of

      • Slow speed capture,
      • produces a very large number of images to process
      • Lack of user control.
      • No image preview

AutoKAP can be automated in a number of ways varying from fuses, rubber band, clockwork, step driven servos, firmware scripted (CHDK) intervalometer, to programmable 2 axis systems.

There is much to be said here on controllers and programming them. There is a discernable ‘AutoKAP style’ which, as well as panoramic capture, produces oddly aligned nadir shots, clipped frames and ‘near miss’ capture, much random shadow play, texture etc etc. I’m beginning to appreciate there is an art to using the auto control to make the best of these aspects; the work of David Thyberg in particular shows what can be done with AuRiCo. I’m exploring this with clickPan-Pro.

AutoKAP rigs can be very light and make best use of simple ‘point and shoot’ compact cameras. An AutoKAP capacity is a useful reserve in light winds as, although the shot selection is near random, it will get some coverage when a radio controlled rig cannot be airborne.

K I T E

In this section I describe the Sutton ff30 as it was the main kite I was using at the time.  No one kite will do it all and as the Sutton FF is now out of production I have re-evaluated the ‘off the peg’ kite choice for KAP. The big advantage of the ‘soft’ kites is their portability, a good replacement for the SuttonFF30 is the Didak Explorer 2.7. I have found the following kites to be an optimum set for the work I do:

1: Bft 2-3: Jones Airfiols 8′ Rokkaku is a very stable light wind lifter with high quality, durable details. Jones Airfoils kites have a well deserved reputation for quality and performance.

JA 8'RokkakuThe balanced combination of weight and strength gives the rokkaku great flexibility and this imparts stability. Rokkakus need the 4 leg bridle tuned before they fly. A solid lifter.

2: Bft 2-4: ITW (Into the Wind ) Levitation 9′ Delta : a very good  kite for KAP provided the spreader spar is replaced with a better one (I used Skyshark 8P carbon) it is particularly good at difficult lanch sites where it can be ‘flicked’ up into smoother air something which is impossible with the paraforms and difficult with the Rokkaku.

ITW LevitationQuick to assemble with interchangeable spars and easy to launch in tight spots, the ITW Levitataion is a great KAP kite.

3: Bft 3-4: Didak Explorer 2.7 takes over when the stress on the ITW Levitation is unpleasant, flown on heavy line it will not invert but heels slowly when overblown.

Explorer 2_7
Powerfull and reilable, sometimes difficullt to launch in sheltered sites , the Explorer is a tough and portable BFT3 -4 option. Needs a drouge on a Y tow line to dampen its tendency to sway. A replacement for the Sutton Flowform 30.

Bft 4-5: PFK (Paul’s Fishing kites) ‘Nighthawk‘ delta, given enough lead over the camera this robust little kite will stay up in really blustery conditions. Similar launch characteristics to the ITW levitation.

PFK x640The PFK Nighthawk is a very lively kite that will stay up in very blustery conditions. It is of heavy duty construction so it can’t be expected to work in light winds.

There are many kites to choose from and the important thing is to get to know how they behave in a variety of conditions before trusting them with lifting a camera.

ff30_01x640The Sutton Flowform 30 (30 Sq ft / 2.7 m2) is a very stable kite and handled with care (appropriately tailed or drogued) it will function in a wide variety of wind speeds. It can be awkward to handle at launch, especially in light winds, but its stability (particularly if the modifications developed by Christian Becot are carried out) is exceptional. The kite needs a minimum of 3.5mph wind-speed to lift a camera and rig of about 700g.  One disadvantage of the flowform is that it can only be manoeuvred by moving the point of anchorage; it is not a kite that can be ‘steered’ in light winds the way delta kites can. The Sutton flowform is a development of the Jalbert parafoil design which has tremendous lift properties by exploiting a very light weight, air filled, aerofoil pattern.

Steve Sutton (b 1946) began his sport parachuting career in 1965 at the age of 19. He was a member of Canada’s National Parachute Team from 1970 to 1972. He competed in two World Championships, winning silver medal in men’s accuracy in 1972. In the early 1970s, Sutton started modifying his parachutes to improve their flight characteristics and stability. A few years later, he used his aerodynamic concepts to develop a series of kites of different sizes.

Sutton foil x640 As Sutton developed and tested his designs, his goals were to harness the abundance of high-pressure air in a foil-type kite or parachute, and use it to create both thrust and stability. The features he developed (and later patented) included a series of vents in the top and bottom surfaces of the wing, and a large vent in the trailing edge. All flowform kites have very deep profiles. These large cells provide a stronger and more stable structure. Although one would expect this to result in a huge amount of form drag, in fact, drag is greatly reduced because of the large volume of air that passes through the kite. This explains why the kite is so light on the line, even in heavy winds. As well, the flowform is self-regulating, maintaining constant flight characteristics despite changing wind conditions. This is because the kite adapts to different amounts of air flowing through it. Sutton’s concepts had never before been used in the field of aerodynamics. The original airfoil-type parachute design by Domina Jalbert, and later developments by others, were all limited to using the air entering the front of the cells to maintain inflation (hence the name “ram-air”). Sutton’s concepts were new in that they allowed differing air pressures to flow through the structure in a thrusting and stabilizing fashion. The result was a kite with excellent flight characteristics.

In 1984, Sutton granted a license to Air Affairs Inc. of Hatboro, Pennsylvania as the exclusive manufacturer and distributor of the flowform.

Thomas-Michael Rudolph 1998

http://www.fang-den-wind.de/ff_devel_eng.htm

Parafoil and paraform

Domina Jalbert (1904-1991) was born in St-Michel-des-Saints (Quebec). Still in his youth, his family moved to Woonsocket (Rhode Island) where he received American citizenship. An early aviation pioneer, Jalbert obtained in 1927 private pilot license no. 626. Growing up with a passion for kites, he conceived huge advertisement kites (with the help of his mother at the sewing machine). With war approaching, he was hired by the United States Rubber Co. for the design of barrage balloons that defended London against air attacks. His first major invention, the “kytoon”, came from this period. A combination of “kyte” and “balloon”, it has since been used for aerial photo, radio antenna deployment, atmospheric research, the lifting of heavy logs, etc.

J foild patent x640 Jalbert founded in 1949 the Jalbert Aerology Laboratory, soon involved with parachute design. In 1953, flying his Beechcraft airplane, Jalbert had a sudden inspiration: why not build a parachute with the shape of a wing? So came to be the “parafoil”, a flexible wing with cells open to the flow of air, generating lift. Granted patent in 1966, the parafoil generated immediate interest and was considered by some as the most radical departure in parachute design since Leonardo de Vinci. The parafoil (nicknamed a “flying mattress”) was rapidly adopted by the American parachute team Golden Knights. Also known as ram air parachute or square parachute, the parafoil is however very different from a standard dome chute in the way that, as Jalbert explained: “the parafoil was not invented as a descending device, but as an ascending one”.

Forerunner of paragliders and traction kites used for paraski and kitesurfing, the parafoil was also tested by NASA for space capsules re-entry. Recently, NASA resumed parafoil testing with the (now cancelled) X-38 CRV prototype. The future crew return vehicle glided back safely to earth suspended under a giant 7,500-square-foot parafoil wing (almost one and a half times the wing span of a Boeing 747 !). One previous world record was held by Jalbert himself who, in 1980, flew a huge 3,640-square-foot parafoil kite. Generating more than 10,000 pounds of lift, the kite was attached to a truck filled with 20 tons of gravel. In 1983, a gigantic 10,000 plus-square-foot parafoil kite was also tested.

K I T E   P H Y S I C S

Kite diagram 1A simple model of a kite in flight can be seen as a balance of 3 forces: airflow (m/s) lift (N) and drag (kg/m2). It is possible to calculate the available lift for a kite at a given wind-speed using the Lift equation:

L = Cl x A x R x (0 .5 V 2)

Where

L   = Lift

C1= lift co-efficient for a low angle of attack given as [(2 π) a]

a   = angle of attack (in radians) (180 degrees equals π radians)

V  = wind velocity

R   = standard air density value (given at sea level as 1.229 kg/m3)

A  = Area of kite active surface (m2)

In addition the kite shape and downwash effects of ‘spilling’ the air around the kite need to be taken into account. The co-efficient value for ‘CL’ needs to be modified:

Cl = Clo / (1 + Clo / (π AR))

Where

Clo = Ist unmodified co-efficient [(2 π) a]

AR = Aspect Ratio of kite (defined to be span ‘s’ squared divided by the area ‘A’)

I would like to be able to calculate the theoretical lift for my kites but I can’t get this to work properly. The unmodifed equation works out like this:

Say

V (wind speed) = 5m/s(Bft3)

A (kite area) = 3m

a (angle of attack) = 0.785rad (45deg)

r (airdensity) =1.229 kg/m3

C1 = (2 π) a= 4.932

then

L = Cl x A x R x (0 .5 V 2)

4.932 x 3 x 1.229 x (0.5X 25)

L= 227kg!!

that’s way too much. Looks like a decimal place error, 22.7kg is close to what my ff30 generates in Bft3.

F L Y I N G   L I N E

I use 260m of 110kg (250 lb) test Dacron and 500m Climax ‘Powerline Extreme’ Coramid 250kg (500=lb) on 10” ‘Halo’ spools.

Rough guide to required line breaking strain:

Work out the approximate wing area in square metres (FF30 =2.7m2 ) Multiply this figure by 30 for light winds, 50 for normal flying, and at least 80 for breezy conditions – to get line breaking strain in kilos.

“While some experienced fliers manage with one reel-and-line for everything, they are careful to select the right kite for the wind, much as a golfer chooses the right club for a given shot. On the other hand, if you have only one kite, then you will need light line for the light wind end of its wind range, heavy line for the strong wind end, and perhaps an in-between line for in-between winds. There’s really no way around this; light line may simply snap in a strong breeze, and heavy line will weigh the kite down in light winds. If the line starts “singing,” then it’s time to get the kite down fast, before getting into serious trouble. If the line’s too heavy, there will be a pronounced “belly” in the line and the kite won’t reach much of an angle.” Dan Leigh 

Managing the flying line

The theory is simple, spool out line as the kite asks for it and wind it in when you’re done, flying a kite is simply a matter of keeping an even tension on the flying line, pay it out on the way up pull it back on the way down. In practice the line will burn your hands, be impossible to keep hold of and tangle more readily than hair on a brush.  Looking after the line is an aspect of kite flying that demands patience, good quality flying line is hard won and needs to be looked after.

Winding x640Avoiding tangled line

There is a natural tendency to wind in the kite hand-over-hand which imparts an ever tightening twist to the line, especially in light winds when line is hauled in quickly. This twist causes the line to wrap around itself and tangle.

There are 3 steps to avoid getting the twist in the line:

      • Lay the line in several small piles rather than a single heap as you haul in.
      • When the kite is down, pull out the line from the kite end to un-ravel the spilled line, if you work from the reel end you will be pulling the line out from the bottom of the pile and it will jam. Lay out the line as straight as you can.
      • Wind in the line with the reel in your left hand if you are right handed (in your right if you are left handed), this feels awkward (which means you are doing it right) but this reverses the twist made by the hand-over-hand winding at haul in.

Using a fishing line swivel at the kite bridle is not recommended, they do not have sufficient strength to take the forces involved with a KAP kite under load.

Gloves

I cannot stress enough how important gloves are: if you are flying a kite which you expect to pull a camera into the air you will cut, burn and probably permanently damage the nerves in your fingers unless you protect your hands. Gloves will give you better grip on the flying line, allow you to pay out line as the kite demands it and give you more time to secure the line than with bare hands. As all the force of the lift of your kite is applied through the cross-section of the flying-line the pressure at the point of line anchorage is huge! Flying gloves of leather are best and they must be replaced when your flying line is felt against the skin of your hand, they are never going to be fashion wear but you must never be without them. Line burn is a risk even when your kite is on the ground, when winding in the line your gloves save your hands.

Gloves x640

Choice of gloves is more important than I first thought, you need grip and protection but also flexibility- some of the cheap ‘work gloves’ are awful and make you clumsy. Kite line will cut gloves like butter if you let it. The ideal would be a pair that would allow tying and untying of knots, working the camera settings and protecting hands from line burn. Such gloves exist and I wear then until they fall apart, these are the best qualty gloves for leisure gardening I have found. They need to be worn in…and when they are its about time to replace them!

Knots

There are 2 knots I had to learn:

The Bowline to tie the kite to the flying line

Bowline

http://www.animatedknots.com/bowline/index.php?Categ=climbing&LogoImage=LogoGrog.jpg&Website=www.animatedknots.com

The double fisherman’s bend (also known as the grapevine) to join lengths of line together: this knot has been tested extensively and found to have the greatest strength; it can be tied as a triple or more if need be.

fishermans bend

http://www.animatedknots.com/doublefishermans/index.php

Damage to line

Even the best quality line will suffer damage from friction. If the line is caught on anything it must be inspected carefully for damage, if there are any signs of wear to the line cut out the damage and tie the line with the fisherman’s bend.

Spool types

A simple ‘Halo’ ring provides good storage for the flying line but tends to place a twist on the line when winding in. A spooling reel (e.g Stratospool) is an alternative but spools will fail after repeated use as they are crushed by the compound forces of the tensioned line. The reel must be able to take the stress of winding in the line under load, this can be considerable and consequently mechanical winders that can cope are big bulky affairs the, best of which are known as ‘Deep sky’ Reels with 12v power types such as the ‘Kristal 635 Variable Speed’  are an option for vehicle or boat mounting.

Harness

A harness lowers the pivot point and distributes the stress of the flying line load across the hips of the flier thus providing a stable attachment for the kite line. A quick release method of attachment (such as a mountaineer’s ‘figure of eight’ descender) is desirable as the kites demand for line should not be unnecessarily impeded. As the load often fluctuates a caving harness is preferred as it is designed to take a greater amount of abrasion than climbers. Using a harness for kite flying takes practice, it may not always be needed but the flier must be able to use it safely without compromising the control of the kite.

T H E  4  K I T E   F L I G H T

To cope with a variety of wind speeds a selection of kites is desirable, the objective is to have a flight of kites that will cover a full range of wind-speeds and still lift the rig. The flight described here is based on my own experience: there are many options! My choices are made on how easy it is to carry them around on a bicycle and how easy they are to assemble and launch. The Sutton Flowform 30 is by far the most used kite of the 4. They are all ‘off the peg’ kites building your own is fun (the ‘soft’ kites are quite difficult though) but you will need to be very confident in your work if you are going to trust a precious camera to your handicraft.

Colours in motion ‘Lifter ‘

  • Flexibility: Light winds only. Flown on light weight ‘Powerline Extreme’ Coramid line to maximise lift.
  • Stability: tends to weave a bit compared to the flowforms. Dangerous in overblown state. Must be drogued to reduce tendency to inversion.
  • Handling: it’s a difficult kite in wind speeds above 7mph!
  • Robustness: Shroud-lines need to packed carefully to avoid tangling.
  • Area=4m2
  • Wind speed Bft 2/ 5-7mph /8-11kph.

Difficult to launch in wind shadow, dangerous if overblown.

Sutton Flowform 30, ‘Becotised’*¨

  • Flexibility: flies across a wide wind range ( 3.5 to 16mph).
  • Stability: good in most conditions, must be dampened with a drogue to deal with gust.
  • Handling: can be a pain to launch in light wind and is very susceptible to collapse and inversion in rotor and vortex effects.
  • Robustness: very hard to break but stitching needs checking if over-flown in high wind speeds (16mph+).
  • Area= 2.7m2
  • Wind speed Bft 3 /6.5-12mph /10-19kph.

HQ Flowform 2.0, ‘Becotised’*¨    

  • Flexibility : Fly in fresh winds only.
  • Stability:  Always flown with a drogue- dreadful in near ground turbulence
  • Handling: Copes with Beaufort 4 easily, its weight balances its pull nicely.
  • Robustness: It’s made of heavy weight fabric so it is heavy (therefore rubbish in light winds) but robust.
  • Aea= 2.0m2
  • Wind speed Bft4 /12-20mph/ 19-32kph

I have had 2 occasions when this kite has been overblown and the condition was catastrophic, it spins, this is recoverable to a degree but best avoided. I have now down rated it to a Bft 3 kite on a light 150kg line.

Paul’s Fishing Kite ‘Nighthawk’ Delta¨   

  • Flexibility: rated at 5-40 knots (6-46mph, up to Bft7!) won’t lift a rig until flown in at least 15mph.
  • Stability: tends to dance about at launch and landing, takes high wind speeds well. Twitchy. Flown with shock-cord damper below kite and above rig.
  • Handling: typical delta- needs care on recovery, noisy!
  • Robustness: Well made from heavy duty materials, awkward to transport.
  • Area=1.06m2
  • Wind speed Bft5 /15-30mph/ 24-48kph

*modified according to aerodynamic research by Christian Becot for increased stability   http://www.becot.info/tako/anglais/e&tako_1.htm

W I N D

Understanding Airflow

The basic principle of the kite is simple: the drag imparted by its surface is converted to lift by the angle of attack of the kite, provided the mass of the kite and its line are less than the pressure of wind acting on its surface. Getting to know what to expect in a given set of conditions takes time and it is this experience which marks out skilled kite fliers; they know how to get the best out of the wind because they have learnt to match the wind-speed to a kite adapted for it, they also know when the wind tells then to go and do something else.ff30 heeling

Man and windMaking the wind work for you is something millers and sailors have, within the limits their capacity to harness nature, mastered. Understanding the limits and the consequences of ignoring them is vital; a kite can multiply the force of the wind by close to the cube of its area: our ability to handle such forces safely is crucial to avoid injury or loss of life. Ships have been dis-masted, crews sacrificed, mills have been wrecked with harvests laid waste and mountaineers lost when the wind is not given the respect it deserves.

Wind is not a continuous force, it constantly fluctuates in waves, the nature of the forces caused by airflow shift constantly and using the wind to gain a stable platform is something of a fool’s errand, however, in pursuit of a unique vantage point for a camera, a good kite and a well designed rig can mitigate a lot of the inherent instability in the balance of lift, mass, turbulence and camera performance.

Aerofoil effects

Parafoil and paraform kites (including flowform designs) have the capacity to exploit the aerofoil effect caused by their shape and angle of attack. The Bernoulis theorem famously states:

As air passes below the wing it also passes above the wing.  The air on top of the wing moves a longer distance over the curved surface of the wing and moves at a faster speed.  This reduces the pressure above wing. The air below the wing moves slower than the air above the wing. This causes the air pressure to be increased.  This difference in pressure above and below the wing causes a wing to fly or lift.’

Right: Sutton Flowform 30 in 15mph wind, the heeling should be controlled with a tail or drogue.

Flying an aerofoil is thrilling as the lift generated happens immediately the airflow allows it and the flier must respond accordingly, the sport of power kiting centres on this effect. For KAP the aerofoil effect gives more lift for a given wind speed than a simple sail but in light winds this effect is absent.

B E A U F O R T S C A L E 2k wide_04In his own words with captionFrancis Beaufort’s scale in his own hand, 1806. It was prepared for improved accuracy in Admiralty records and incorporated ideas from the lighthouse engineer John Smeaton.

In general up to Beaufort force 5 is safe to fly a KAP kite, anything over that and SERIOUS PROBLEMS MAY OCCUR. The exceptional design of fishing (e.g. Paul’s Nighthawk) kites can handle more but strong winds are turbulent; you will find lift will suddenly fail and, as you begin your recovery, the pull suddenly becomes uncontrollable often catching the kite out of balance with the risk of ‘power dive’ ending all.

Beaufort 2, 3 and 4 (between 3.5 to 15 mph) is my comfort limit; Beaufort 5 can be managed with the right kite if the gust or peak speed is less than about 22mph.

Variation in airflow:

Weather system characteristics

Wind is a dynamic force it is never constant and can pulse in power (gust) over a variety of cycles. Gust patterns can vary they have a maxima of up to twice the nominal wind-speed and minima of no variation other than a few percent of the average. Big gust effects are common in cyclonic conditions and less so in anticyclones.

Local effects:

Rotary turbulence is caused by almost any obstruction to airflow; it is also triggered by channelling effects under bridges along cuttings and embankments. A ditch across an apparently flat field can produce a disruption to a smooth airflow if the wind direction is either along it or directly across it.

Laminar flow is the characteristic of a smooth flow, the higher up you go the stronger the wind! It is common to have a very turbulent lower layers and increasingly smooth layers above.

Buildings create difficult airflow to fly in, this includes very dangerous shear effects: in order to photograph buildings close up a long lead line should be let out before the camera is launched.

Trees in leaf create disturbances in the airflow up to 3 times their own height.

Matching the kite to the airflow

By using a drogue the lift /drag characteristic of the kite is altered, this can effectively extend the high end of the wind range of the flowform pattern kites successfully. Although the turbulence of some airflows is unmanageable the drogue exerts a dampening of the lift by adding a drag force that is constantly proportional to the airflow through it.

SUTTON FF30 (2.7m2) : APPROXIMATE LIFTING CAPACITY
Minimum mph

Beaufort

Lift

Flying Angle

Camera

Peak mph Gust
3.5
Lifts kite and line alone
Low
(30deg to ground)
6
6

2

Lifts 700g rig
Low
(30deg to ground)
Canon Ixus
8
7
Lifts 850g rig
High
(45-50 deg to ground)
Panasonic LX3
12
8
3
Lifts 920g rig
Low(30deg to ground)
LX3 Camera with wide angle lens adaptor
13
(drogue required)
HQ 2.0 (2.0m2): APPROXIMATE LIFTING CAPACITY
Minimum mph

Beaufort

Lift

Flying Angle

Camera

Peak mph Gust
6
2
Lifts kite and line alone
Low
(30deg to ground)

8

7

Panasonic LX3
12
(drogue required)
8
3
Lifts 700g rig
13
(drogue required)
12
Lifts 850g rig
High
(45-50 deg to ground)
15
(drogue required)

The boundary layer

In the Earth’s atmosphere, the planetary boundary layer (PBL) is the air layer near the ground affected by diurnal heat, moisture or momentum transfer to or from the surface. In physics and fluid mechanics, a boundary layer is that layer of fluid in the immediate vicinity of a bounding surface.

The boundary layer is the layer a kite flies in. The height of the boundary is varies according to wind-speed, location and pressure, kites will rarely escape the PBL (with the exception of marine and artic environments) consequently an understanding of how turbulent, non-laminar flow affects the behaviour of the kite is important.

Layers in the boundary layer

In the planetary boundary layer turbulence is produced in the layer with the largest velocity gradients that is at the very surface proximity. This layer – conventionally called a surface layer – constitutes about 10% of the total PBL depth. Above the surface layer the PBL turbulence gradually dissipates, losing its kinetic energy to friction as well as converting the kinetic to potential energy in a density stratified flow. The balance between the rate of the turbulent kinetic energy production and its dissipation determines the planetary boundary layer depth. The PBL depth varies broadly. A given wind speed, e.g. 8 m/s, (18 mph) will have a co-responding local rate of turbulence production, such that a PBL in wintertime Arctic could be as shallow as 50 m, a nocturnal PBL in mid-latitudes could be typically 300 m in thickness, and a tropical PBL in the trade-wind zone could grow to its full theoretical depth of 2000 m.

In addition to the surface layer, the planetary boundary layer also comprises the PBL core (between 0.1 and 0.7 of the PBL depth) and the PBL top or entrainment layer or capping inversion layer (between 0.7 and 1 of the PBL depth). Four main external factors determine the PBL depth and its mean vertical structure: (1) the free atmosphere wind speed; (2) the surface heat (more exactly buoyancy) balance; (3) the free atmosphere density stratification; (4) the free atmosphere vertical wind shear or baroclinicity.

http://en.wikipedia.org/wiki/Planetary_boundary_layer

P R O C E D U R E

Illustration from John Bates 1634 ‘Mysteryes of Nature & Art’ description of a ‘Fiery Drake’ (fire dragon) or firework lifting kite. Copyright: British Library

Basic kite dynamics:

 

  •  Large kites are inherently more stable than small ones.
  • A correctly sized drogue or tail stabilizes the motion of a kite.
  • Symmetry is all. A kite out of balance is a disaster waiting to happen, get it down and balance it!
  • Kites that ‘spill’ airflow (by allowing a portion of the flow to pass through them) will do better at higher wind speeds than simple sails.
  • Soft kites fare better than framed ones with higher wind speeds as they have no spars to break BUT unless properly designed buffeting can close cells and cause a soft kite to collapse.
  • In light winds the weight of the line can cancel the available lift
  • Under load (i.e. lifting a rig) the bridle angle will be steeper than without loading.
  • There is an optimum angle of attack for any given kite which is the angle where lift overcomes drag. In other words the angle at which the kite is blown upwards against the restraint of the line not along.
  • Sudden load increases caused by gusts mean the flying line must have a tested breaking strain which should be at least double the anticipated load.
  • A spool reserve (and space to use it!) is needed for kite control as the attitude of a kite under extreme stress can only be corrected by reducing the forces in it: without slack line to pay out you will be forced to run towards the kite.

Matching kite to wind speed:

There is no one kite that will fly in all winds. In theory a big light kite will lift best in light winds and a smaller strongly built one will be best in stronger winds: in practice the range of wind-speed for a given kite can be extended a bit by adding a drogue or tail (with some loss of flying angle). The increase in pull caused by gusts in stronger winds can be catastrophic for a large light-weight kite.

(Adapted from Tgran posted on flickr)

‘All kites have their wind ranges (from barely lifting to out of control). In calm breezes (where it’s easiest to learn this stuff) the FF8 is a little bit of a toy. Its fun, but it won’t lift your cell phone consistently. I’d get (or build) a fled kite as it will be more generally useful in the 6-13 mph wind range. You really will need a 12 mph or so breeze to get the FF8 + rig off the ground and if the wind is rough it won’t be good for the longevity of your camera. It’s much harder to learn this stuff toward the upper end of the wind range.’

Up to Beaufort force 5 is safe to fly a KAP kite, anything over that careful consideration of the behaviour of the kite is needed otherwise  SERIOUS PROBLEMS MAY OCCUR.

Strong winds are turbulent; you will find lift will suddenly fail and, as you begin your recovery, the pull suddenly becomes uncontrollable often catching the kite out of balance with the risk of ‘power dive’ ending all.

F L Y I N G

The fliers’ stance of stiff neck and hunched shoulder as depicted in the picture of the ‘firey drake’ will be familiar to modern day fliers. Relying on the grip of your hand (preferably gloved) when flying a kite with sufficient pull to lift a camera is risky in all but the lightest winds; use of a harness is recommended.

Key points:

  • Be patient
  • Assess hazard and risk to you, your kite and those around you
  • Make sure you have room to move
  • Get a feel for the wind where you are
  • Test the lift above your local envelope before you commit the rig aloft
  • Watch the kite at all times
  • Know when to give up and try again on another day

 F L Y I N G  F O R   P H O T O G R A P H Y

 The time of day and state of sunlight are crucial to success. Consider the effect of :

  • Grazing Light, early morning, late evening (also be aware that lift changes at these time too!)
  • Midday lighting, summer and winter
  • No sun, overcast skies may give a useful flat light in some cases
  • Camera settings and filters to balance sky and ground illumination

L A U N C H

When conditions are right it’s simple but it can try your patience when you are unfamiliar with the airflow. Watch for any sign of the nature of the flow…..place yourself as far from obstructions as possible…find the ‘sweet spot’ where you are away from vortices and in a clear airflow. Stand with your back to the wind, let out line and pull back on the kite; enjoy the thrill of flight!

Know your kite

Some kites are very unstable until they have achieved the correct angle of attack; they loop madly, demanding slack line as the kite begins to turn over and then tight line as it is upright until balance is achieved. Typically you will have to dance with the kite moving quickly in the first seconds of launch and then less so as the kite corrects.

Know the site

If you are attempting to photograph buildings beware the effect the building will have on airflow. If the launch site is surrounded by trees and buildings you may well be standing in a place the kite can’t be launched from!

Know the wind

Light is good, strong is bad; you need to know just how light a wind your kite and rig will work in. Always spend a little time to assess the available lift with your chosen kite before committing the rig to the flight. If you have a selection of kites available you will be able to match the best kite for a range of wind-speeds.

Know your rig

Be ready with the rig and make sure it will lift cleanly, don’t try to winch it by pulling the kite up, if you have to resort to running backward pulling the kite to lift the camera you have probably committed in too light a wind. As the rig ascends its mass will affect the attitude of the flying line to the kite, be ready for this; the effect can be violent and start an unwelcome cyclic oscillation, if your rig suspension is properly designed the movement should dissipate quickly.

Bft 2 envelope1st attempt at a ‘KAPspace’ diagram. At Bft 2 the down wind distance can be more than double the height achieved. An increase in wind speed of a mere 5mph can reverse the distance to height ratio. The size and sweep of the ‘saftey  box’ is variable according to wind speed, wind diection, kite size and load.

Clothing

Wear gloves!

Wear a harness or climbers sling with a ‘figure of eight’ descender and a ratchet.

You are going to stand in the wind, wear appropriate clothes.

Keep a knife in your pocket.

You are going to be staring into the sky for longer than normal: wear shades.

Once you have the kite aloft you will probably be unable to put more clothes on or take any off, be ready to make the best of what you are wearing once you have committed the kite to the wind!

F L Y I N G   H E I G H T

It is not a straight forward matter to determine the height of a kite above the ground. A rough method is  to use a clinometer to determine the vertical angle to the kite (q) and estimate the hypotenuse (h) as the length of the flying line with the accepted catenary of the line as giving a false reading of (Sin q )h; the method has the benefit of simplicity but it is not accurate.

A light weight altimeter which will relay height data as an onscreen display via the camera video-link is available from James Gentles:

Alti OsdThe GentLED ‘altiOSD’ altimeter.

The Gent AltiOSD is no longer available. I now use  ‘Immersion RC’ GPS/EasyOSD devices which are heavier and draw more current.

H A N D L I N G   T H E   F L Y I N G   L I N E

The tension must be constant and the kite will rise against the line, avoid sudden tugs and play out the line as fast as the kite demands it, height is safety so don’t try to attach the camera until the kite is well into a smooth airflow with a constant pull against you, adding the rig to the line will pull it down so you must estimate how much lift there is and balance it against the mass of the rig.

L I N E   R E C O V E R Y

Winch/haul down

Given the right lift to load ratio, it is possible to haul line fast enough for the kite to maintain lift and get the rig back safely almost every time. This technique works very well for small kites and light rigs.
Aside from calamitous drops of wind, hauling the line down at the end of any KAP session can be very therapeutic and in difficult conditions is the fastest way to get the kite down through a turbulent transition zone with control on giving and taking line if the kite misbehaves.
Spread the line out as it spills to avoid a single heap of loose line by paying it out in zigzags on the ground. Walk towards the kite drawing the line in as the pull slackens then grip the line and walk the kite upwind to begin the walk again.
Lastly, line grip when hauling. This is the bit I thought intuitive, but I’ve seen quite a lot of other fliers do not do this. To greatly reduce the risk of line slipping, and potential line burn, (but you are using gloves aren’t you?) as you grasp the line turn your hand 90 degrees towards yourself as you haul. If you’ve not tried this, you will be surprised at the improvement in grip on the line. Although there is a risk to your hand if the pull is too strong, taking a half turn of line over your hand will give you enough grip to momentarily shift the free hand to tie off the line or advance up the line, this needs careful judgement and flies in the face of the ‘never take a turn around your hand’ sailors rule: always be ready to free your hand in a gust.

Adapted from Simon Harbord at http://steel.ced.berkeley.edu/cris/kap/discuss/comments.php?DiscussionID=907

Walk down

If space allows and you are confident the line length between you and the kite will fit in the space you are in with out fouling obstructions then anchoring the line and walking down it sliding the line under your hand using a glove, strop or pulley will bring down the kite easily, Take care to avoid abrasion or sudden release of the line as the tension can offer fierce resistance to any object used to slide along it. Be careful to let heat dissipate clear of the line, keeping the traveller moving will avoid this.

Damage to flying line

Check for wear at the attachment points for the rig and tie off, its surprising how often these occur at the same points on the line and cause abrasion. Take care to anchor the line clear of sharp edges and inspect it when untying for marks that could indicate stretch or wear.

Walk down Ratchet

A modified ratchet block is an extremely useful tool in recovering the kite. If the wind speed increases with the kite aloft getting it back down again can be difficult. Chris Benton found a racing dinghy ratchet block was perfect for the job after the modifications shown. Photo diagram by Chris Benton.

KAP Field Practice & Procedure

Having got to the flying field some important decisions must be made. Having a number of targets in mind is useful, if one site doesn’t work out having an alternate could save the day. Pick your day on the basis of the best forecasts available, you need wind and sun for this! If you are working as a pair procedure will be different than working solo, if extra hands are willing they can be put to good use carrying kit, swapping camera control, keeping spilled line tidy or even as ‘foreground’ interest in photos.

Remember there is no shame in calling off a flight if you are not comfortable with any aspect of what you propose to do: your kite, camera and photographic standards are not worth risking.

Wind, light and viewpoint

The view downwind will be easiest to work with, there will be a good match between what you see on the ground in that direction to what the camera sees. The view directly upwind will tend to include the flying line. Illumination is crucial to success and strong light will generally give better results than soft. Sunlight on the subject is desirable, sun at right angles to wind direction gives good results. Shooting into the sun can give dramatic effects but glare problems will be greater for an airborne camera as the horizon will tend to be ‘wider’  than a ground based one, for this reason a polarising filter should be used. The exposure of clouds will be improved and the ‘flare‘ from ground reflectance will be reduced with a polarising filter. Lower sun angles will always be more interesting than higher but at the cost of lost information in shadow.

In preparation for a KAP flight the following steps have proved successful.

  • Assessment of the launch site, wind conditions and downwind view of target. Wind at your back with Sun to the Left or Right is ideal. You may find the wind direction and sunlight won’t let you do what you want to…pack up and try again later, nothing you can do will change the weather, pay more attention to the forecast next time! A bit of map work before you set out will pay off on the day.
  • Time, do you have time to achieve what you want to do? KAP is best not rushed, you will only have mediocre results if you do not ‘feel’ your way into the wind, and that takes time. Waiting for the light will pay off if the forecast justifies it…waiting in hope is a fool’s game.
  • Alternate launch site. Consider alternative lunch site and walk-in options, you may well start off in an easy launch site but have your path to the target blocked. It’s far easier to walk the kite down wind (it will be in front of you) but the walk opposite the launch site may give you an easier walk in.
  • Check available resources, tie-off points, people who can help. If you are working solo you will have to be fully kitted up with harness, knife, dog-stake and recovery gear before launch.
  • Assess risk, check for overhead obstructions, wires, trees, poles and posts, traffic (cyclists are very vulnerable to kite line), animals (horses are spooked by a low flying kite, be prepared to down the kite and let riders pass), people, air traffic, wind direction variation. Distraction hazard is worth considering, will your kite attract the attention of anyone who should be concentrating on something safety critical like driving a car or operating a chainsaw?

Kit prep, select

  •  kite and drogue,
  • rig: AutoKAP vs.  full control,
  • camera: heavy or light,

according to what will work in the available wind. Lugging a selection of kit gives you more options: Having an AutoKAP rig, an alternate lightweight camera, high and low wind speed kites, drogues etc. all extend the chances of success.

  • Protect your kit from dirt and damp as much as possible, pack away and carry with you anything you don’t use, the chances are you may not return to the same spot once you are airborne, the old survey adage ‘never turn your back on your kit’ is true for KAP, once the kite is aloft your concentration will be focussed on other things. Don’t forget a systematic method of putting stuff away in the same place will strengthen your chances of not missing a vital component next time you need it.
  • Assemble rig, attach pendulum, examine mounting point: ANY evident damage at this stage should abort the flight.
  • Much of the RC drill below has been superceded by use of 2.4 GHz RC and 5.8 GHz video relay. The start-up sequence is no longer sequential, the antennae are tiny and therefore robust. The main difference is the power consumption of the higher frequency kit, keeping stuff switched off until needed and carring spare batteries is important.
  •  attach antennae, a 3 point fixing is needed for the RC Rx antenna
  •  observe Tx/Rx power on priorities: RC Tx must radiate 1st!
  •  check camera and shutter actuation, adjust PL filter to horizon opposite sun, set burst mode,
  • connect camera to video relay,
  •  power up and connect receiver and screen, test signal, remove lens cap
  • zero altimeter.
  • Pilot launch: If uncertain about which kite to use launch one and see how much pull there is in the ‘clean’ air to confirm your choice. Never launch the rig unless there is sufficient lift.
  • Let the kite find its lead length. If the wind is light let the kite rise until you feel the pull is enough, and then let it rise a little more in anticipation of the weight of the rig.
  • Brief team, when you are happy with the behaviour of the kite it is a good time to advise all involved on the risks before you commit the rig, after all you are about to hang a weight above their heads.
  • The more people know about what’s going on the happier they are (although you don’t want to be the centre of a crowd scene).
  • In most cases the biggest risk to immediate bystanders is line burn during launch and landing.
  • Let people know where they can see the results; it does no harm and engenders a friendly attitude.
  • Attach assembled rig to flying line. Get some slack ahead of the desired mounting point. Check for abrasion risk on the cleat. Attach cleat end upwind, snap clip over the flying line.
  •  Clothing, do all the team look like they will be able to watch the sky, handle line and survive the weather ok? A good flight will be hours long. Gloves, sunglasses, long-sleeved tops, sunscreen may be required.
  • Permissions: should you have asked anyone who might object to what you are doing first? Dealing with upset people while you are flying a loaded kite is best avoided; you can’t run or hide with a big kite attached to you.
  • Watch the kite at all times. Once aloft the kite flier has only one job, keeping the rig safely aloft, all decisions about how this is best achieved are up to the flier. If the air flow becomes unstable or there is a loss lift the decision to get out of the sky rests with the flier.
  • Move with caution, there is a sort of slow motion effect of walking with a kite, sudden movement is undesirable.
  • Walking down wind will lower the kite and time must be allowed for it to recover.
  • Smooth motion in paying out line will help the stability of the kite
  •  Reeling in can demand quick action to maintain flight, the flier must be alert to this, especially with a heavy camera.

 and finally…

Don’t panic! There is a way around most difficulties and the more practice you have the more apparent this is. The rig can be hauled down, the flight called off and lessons learned provided you have the means to recover the kite. It is easy to fall into a rushed state of mind but when the kite is aloft you have as long as the wind is blowing and the batteries hold up to get your shot.

Kite Aerial Photography R I S K   A S S E S S M E N T

Overblown kite

Knowing the limits of kite performance is crucial to matching kites to appropriate wind speeds. Reacting to early indication of an overblown kite can avoid serious problems. A well made kite may well not show any signs of failure before it is overcome by the imbalance of forces acting upon it, being aware of how to ‘read’ an approaching failure before things get out of hand is well worth the time taken in testing conditions before committing the camera to flight.

What is the overblown condition?

Simply put a kite is overblown when the wind pushes it out of the sky. The early indications of this may not be obvious from the flier’s point of view, particularly if using an unfamiliar kite.

Overblown

As seen from above Top left:. The kite is pushed upwards when its lift capacity is generated by wind pressure acting upon its surface. Bottom Right:  An increase in wind speed will eventually push the kite to the edge of the wind ‘window’. The kite will heel to one side, it may recover as gusts subside but a heeling kite in a strong wind is a sure sign of too much kite placed before the wind! If the wind-speed continues to increase eventually the kite will be pushed into the ground. Even if they can keep flying framed kites will snap spars and soft kites will rip stitching if exposed to excessive wind speeds.

Viewed from above a Flowform kite is lifted upward in the down wind direction, an efficient kite with a well matched airflow will rise towards (but hopefully never reach) an over-head position. An increase in airflow will cause progressive instability (usually characterised by the kite ‘heeling’ progressively harder to the left or right of the down wind axis) to the point where the kite is blown into the ground.

Other modes of failure at the overblown state are:

  • Sudden acelleration accross the face of the wind followed by inversion and  powerdive.
  • Progressive spinning with loss of lift.
  • Repeated luffing ending in either a spin or a dive.
  • Spar failure
  • Split seam

What happens?

It depends on the kite but early indications are a tendency for it to fly ‘on its ear’, a parafoil will be close to inversion in this state which will happen suddenly leaving the flier with little time to react. Flowforms do better and can tolerate flying in the edge of the wind window fairly well, the tendency to inversion is less that for a parafoil. Generally the kite is pushed down and out to the edge of the wind envelope. It will lose its ability to lift any load as it is forced across the face of the wind. Gusty conditions make reaction to the overblown state difficult; the obvious tactic of giving the kite more line in the hope that it will rise will only add to the difficulty of the situation when the gust releases its pressure on the kite by either placing it in a higher (faster) airflow or further down wind exacerbating recovery.

The Flowform kite and thermal vortexes

In warm weather light winds thermals can be come the dominant airflow. They are a big problem for ‘soft’ kites. A thermal has 2 components, a rising column of warm air and a descending flow of displaced cool air around it, the kite will be pulled into the descending airflow as you let out line in search of height. You cannot see the airflow caused by the thermal and they will invert the kite and send it either into a power-dive or into an accelerating descending spiral. Flying with a drogue will slow down the effect but the power of the vortex is sudden and destructive to a Flowform kite.

The obvious action of letting the kite have more line (and reduce the speed of the movement accordingly) works but only momentarily as the longer line, when it takes the load of the new airflow will pull the kite back into the vortex. If possible, as soon as the slack line has allowed the kite to recover its attitude move the kite across the sky as quickly as possible (yes, run sideways across or down wind if you have to) to get the kite back into the clean airflow.

If the kite has a tail or drogue it will recover more quickly but the required action is to tow the kite out of the descending air as quickly as possible.

Once in a spin most kites don’t recover (and in fact the spin will speed up us you pull it out of the rotor) until they are given slack line to release the energy of the spin. The flier will need to judge carefully how far the kite needs to be dragged (spinning and falling) across the sky before it can be fed line and righted.

A framed kite will behave in a similar way but a soaring delta can be directed into the up draught as it can fly as a free wing in the way soft kites cannot when the forces acting on them are inverted. The diagrams below give some idea of what the kite is up against.

Wingtip rotorTake a look at the smoke trace of the wing tip vortex spilled by a light aircraft; the size of the disrupted airflow is significant a kite flown into a vortex like this has almost no chance of recovering normal flight unless it is removed from the flow.

Turbulent flowIn the flow diagram, the dye trace reveals the rotary nature of the turbulent flow. When flying a kite there are no such markers. The first indication you get of the rotor is when the kite rolls over and starts to spin.

The causes of turbulence are either local obstruction to airflow (buildings, trees, hills etc.) or thermal displacements cause by differential heating or cooling of the air.

R I S K

Craig Wilson’s list of do’s & don’ts for flying in an urban setting.

D O N ‘T

1. TAKE CHANCES: Never launch into unknown winds. Fly first in a safe, open area so that you know the true wind condition at the heights you will have the kite. The scariest thing would be to have too much kite for the wind up over buildings and traffic.

2. FORGET YOUR RECOVERY KIT: Never be without all your hardware for recovery, tie down, and line handling. Keep all you need with you. Don’t leave it in the car. Don’t leave it with a friend to hold. Don’t leave it on the park bench where you launched thinking you won’t need it till you get back.

3. PUT PEOPLE AT RISK: Never launch or land a kite in an area crowded with people. Launch away from the crowd and walk the kite to the people if that is the shot you want.

4. FLY AT RISKY TIMES: Never fly into an urban environment during times of day when thermals are most active. For me photographically I prefer early and late light anyway, which are times of day when the sun is not producing a lot of nasty thermals. In the Urban Environ strong sun on blacktop parking lots, roofs, and streets, tends to boil up some active thermals that are difficult to control the kite in. Selecting cooler days and moderate wind speeds, along with early morning or late afternoon sun will minimize the problem of thermals.

D O

1. CHECK YOUR KIT: Take time to pre-flight all your equipment, double-check all kite and rig connections. Have a routine just like an airline pilot goes through before a flight and never neglect or minimize its importance. You must be willing to abort your KAP attempt if anything is out of order. An equipment failure can be very dangerous to someone no matter where it happens.
2. KNOW YOUR SAFE LAUNCH /RECOVERY SITE : Launch your kite in a safe, comfortable area that is accessible to your intended target. Let the kite fly for at least 5-10 minutes before connecting the camera rig to be sure that the wind is steady and reliable. Make sure that your kite is up to a height well above buildings in the area that may cause wind turbulence. With the camera on the line but at your hand you can walk into the target site.

3. PLAN the route of this journey so that you are walking down wind. Walking downwind keeps the kite out ahead of you and everything you need to worry about is in front of you and easy to see. If the wind drops or you find turbulence and become uncomfortable you can simply turn around and go back up wind to the safety of your launch site. Be very careful walking upwind with your kite to a target. If the wind begins to lessen you may be unable to walk back downwind to your launch site and you may be left with no choice but to land your kite where you are.

Conclusion
I am in no way advocating that you get your kites and head to the city to try flying in the heart of downtown. I am only saying that it can be done. The risks can be managed and minimized so that it is not all that different than flying in other locations. The most important aspect of KAP in the urban environ is the flying skill and focus of the operator. That skill combined with preparation and planning can mean that you can work your way into what seems to be kite unfriendly locations. The key to your success and safety will fall squarely on your ability to keep an unbroken focus on the task of KAP. If you are so nervous that you are uncomfortable or shaking, if you are unable to deal with all the aspects of the kite, camera, and interested onlookers, then it is not an environment to mess with. It is critical to be able to be in control, relaxed, and maintain mental focus.

When we expose our minds to what we perceive as great risk; running a red light, bungee jumping, standing before a charging rhino, KAPing in an urban environment, we need to train our mind to stay focused or bad things can happen and we can become helpless to stop them. Practice and repetition is how we become comfortable with all the inputs that KAP offers. We can progress from easy sites to KAP to more challenging ones, and we are able then to stay relaxed, focused, and comfortable performing at a high level in areas that might seem to add to the risk.

K I T E S   &   O T H E R   A I R C R A F T

When you are flying your kite you are sharing airspace with others: the rules are simple- you may not exceed a height of 200feet (60m) without express permission to do so. (See Appendix 1) In practice knowing the height of the kite is tricky and the variation in wind-speed can easily push you over the limit or, in some cases render the photographic objective unachievable.

Information on air-traffic

If you are going to be flying at or near the 60m limit it’s worth getting to know where low-flying aircraft are going to be and just what height they will operate at. The Civil Aviation Authority (CAA) and the National Air Traffic Service (NATS) supply regular bulletins and publish charts showing obstructions to air-traffic. The ‘rules of the air’ are based on separation by a safe height between aircraft according to the direction of travel and a minimum flying height of 2000’ except for aircraft in transition (approach, take off and landing), military and emergency aircraft.

Key Acronyms

VFR: Visual Flight Rules

A set of regulations which allow a pilot to operate an aircraft in weather conditions clear enough to allow the pilot to see where the aircraft is going. Specifically, the weather must be better than Basic VFR Weather Minimums, as specified in the rules of the relevant aviation authority (the FAA in the USA).If the weather is worse than VFR minimums, pilots are required to use Instrument Flight Rules (IFR).

VOR: VHF Omni-directional Radio Range

A type of radio navigation system for aircraft. A VOR ground station broadcasts a VHF radio composite signal including the station’s identifier in Morse code (and sometimes a voice identifier), and data that allows the airborne receiving equipment to derive a magnetic bearing from the station to the aircraft. The VOR sweep sector is marked on the air navigation chart and is a good indication of where not to fly a kite at any height: in this sector aircraft will be in transition.

NOTAM: Notice To Airmen

NOTAMs are created and transmitted by government agencies under guidelines specified by Annex 15: Aeronautical Information Services of the Convention on International Civil Aviation. A NOTAM is filed with an aviation authority to alert aircraft pilots of any hazards en route or at a specific location. The authority in turn provides a means of disseminating relevant NOTAMs to pilots. If you intend to fly above 200’ and permission is granted the CAA will post a NOTAM for a fixed period.

NOTAMExample of a posted NOTAM for kite flying. Extract from http://notaminfo.com/nationalmap

ATC Air Traffic Control

Contacting ATC should not be necessary unless you are responsible for a runaway kite in a transition zone!

C O N C L U S I O N

From the experience gained between February 2009 and December 2009 it can be demonstrated with the example imagery in this report that KAP is a viable method of raising the camera for a variety of heritage record photographs.

The reliability and repeatability of KAP is different to other methods of raising the camera such as PAP, UAV or balloon but the cost, deployment speed, height, and duration of capture are all superior when conditions are right.

The positioning of the camera is, depending on the access to the subject, less precise than other methods but the resolution of a wide-angle equipped micro 4/3rds camera with a video downlink ameliorates this.

KAP is one of a group of techniques that should be used together to gain an optimum photo record of heritage assets, its application should be actively considered for low level oblique image capture which is complimentary to standard ground based and aerial cover.   Vertical image cover by KAP is possible and, where achieved, (e.g. Warham Camp) the low flying height generates rich records.

This report gives an introduction to KAP. It is not comprehensive and the following topics should be considered as an important part of an overview of the technique

  • High altitude (300m AGL) KAP (with CAA approval)
  • Use of delta kites at low and high wind speeds- adaptation of kite fishing technique
  • Use of sport (surf/boarding) kites and their adaptation for KAP (I have experimented with the SLARC method on a 9m kite as proposed by Peter Lynn with little success. Sport kites are designed for traction across the middle of the wind window: KAP requires lift at the apex where the sport parafoil is at its most unstable.)
  • Photo-cover metrics
  • 360 panoramic capture by AuRiCo
  • Image processing for montage of multi-perspective imagery
  • Stereo capture
  • Parallel performance with other UAV, PAP methods
  • Review of archaeological KAP applications
  • Certification and training in kite handling at kite sport schools
  • Camera customisation
  • Orthophoto integration of KAP imagery
  • Habitat monitoring

I would like to thank English Heritage’s Metric Survey Team for the privilege of conducting this work as a part of the Digital Recording Strategy; ‘Raising the Camera’ project.

Bill Blake

http://www.bill-blake.co.uk

15/12/10

Elveden Monumant x640

Elveden War Memorial , Elveden Suffolk. Extract from 12Mpixel image taken from a tethered kite at 45m AGL.

Darells Nadir x640Caponier Detail x640Landguard Montage 1 x640

KAP imagery of Landgurd Fort Felixstowe, Suffolk captured with a 12Mpixel camera in 12-15 mph wind. A 2 man team was able to direct the camera to cover the desired aspects of the monument. One operator controls the kite whist the other the camera by both radio control, video down link and direction of movement of the kite.  The low level stand off has recorded the condition of the upper surfaces of the monument as well as the movement of rainwater ponding.

Sources

http://www.armadale.org.uk/kite.htm

http://www.harb85.freeserve.co.uk/

http://www.arch.ced.berkeley.edu/kap/

http://www.hprinzler.de/

http://www.deltas.freeserve.co.uk/

http://www.brooxes.com/

http://www.gentles.ltd.uk/gentled/

http://www.gentles.info/KAP/rig04/cameras.htm

http://www.kapshop.com/

http://en.wikipedia.org/wiki/Kite_books

http://drachenstore.easystorecreator.net/

http://www.ofcom.org.uk/static/archive/ra/publication/ra_info/ra60.htm

http://scotthaefner.com/360panos/kap/?g=360pano

http://www.becot.info/fronton/what_i_am.htm

http://www.geospectra.net/kite/history/history.htm

http://www.kaper.us/articles/ARTICLE_030220_risk_wilson.html

www.olsphoto.com/kapguide.pdf

http://www.wokipi.com/decouverte/aerialpicture.html

http://www.gercoderuijter.nl/index.htm

http://pagesperso-orange.fr/kap-chagny/

Clive Hart:

Kites, An Historical Survey

Paul P Appel Pub; Revised edition (June 1984)

ISBN-10: 0911858385 / ISBN-13: 978-0911858389

Scott Skinner and Ali Fujino Ed, Kites: Paper Wings Over Japan

Thames and Hudson, New York: 1997.

ISBN 050027942X / 9780500279427

Craig Wilson:

Hanging by a thread A Kite’s View of Wisconsin

Itchy Cat Press (August 15, 2006)

ISBN-10: 0976145030  ISBN-13: 978-0976145035

Gerrit Bart Volgers

Terschelling in vliegervlucht by Gerrit Bart Volgers

Private imprint

Netherlands 2006

James and Susan Aber and Firooza Pavri

Andrea Georgopaulos

Low Altitude Non-Matric Photography using a kite

University College London

ISPRS Commission V York 1982

ISSN 02528231

Unmanned small-format aerial photography from kites for acquiring large-scale, high-resolution, multiview-angle imagery 2002

Foster, Karl

Kapping it all, Article in Digital Camera World Magazine

February 2005

IPC Media ISSN: 1366-5324

Raoul C. Fosset

Aerial Photography by Kite

1994 The Drachen Foundation

Gerco de Ruijter
Gerco de Ruijter / Petran Kockelkoren
2004

James S. Aber and Susan W. Aber,

Unmanned small-format aerial photography from kites for acquiring large-scale, high-resolution, multiview-angle imagery,

/ISPRS Commission I/FIEOS 2002 Conference Proceedings

2002

Georgopolous, Andrea

Low Altitude Non-metric Photography using a kite

ISPRS Commission V

1982

Wheeler, David

TIGHAR (The International Group for Historic Aircraft Recovery) KAP Guide

Instructions on use of AutoKAP for site recording at Nikamaroro Island

July 2007

Appendix 1

CAA KAP Permission Aplication Form

Appendix 2

 Kite Aerial Photography and UK Law by David Mitchell

http://www.zenoshrdlu.com/kapstuff/KAPUKLaw.html

This document provides references to some primary documents that define the legal framework within which Kite Aerial Photography operates in the UK. It may be useful in answering such questions as:

is a kite legally an aircraft?

how high can I fly my kite/rig combination?

what R/C frequency band(s) can I use?

One key piece of UK legislation is the Air Navigation Order 2000 (otherwise known as Statutory Instrument 2000/1562). It contains three key statements.

First, it contains a table (Schedule 2, Part A) that classifies aircraft into categories as follows:

Lighter than air aircraft Non-power driven  Power driven Free Balloon
Captive Balloon
Airship
 
Heavier than air aircraft Non-power driven Power Driven (flying machines) Glider
Kite
Aeroplane
Landplane
Seaplane
Amphibian
Self-launching Motor Glider
Powered Lift (Tilt Rotor)
Rotorcraft
Helicopter
Gyroplane

This makes it clear that a kite is an aircraft (heavier-than-air, non-power-driven) as far as UK legislation is concerned. The second important statement is in article 86 which contains rules for Balloons, kites, airships, gliders and parascending parachutes. Paragraph 2b (v) states:  86.2b (v) “a kite shall not be flown at a height of more than 60 metres above ground level”  subject to the proviso “without the permission in writing of the CAA and in accordance with any conditions subject to which that permission may have been granted.”

Although kites weighing less than 2kg were exempted from this rule in earlier ANO’s, they no longer are because the third statement, in article 132, states: 132. The provisions of this Order other than articles 58, 64, 85(1), 86, 87, 118(1)(b), 129(1), (2) and (5) shall not apply to or in relation to: (a) any small balloon; (b) any kite weighing not more than 2 kg; (c) any small aircraft; or (d) any parachute, including a parascending parachute

Since article 86 does apply, kites in the UK are restricted to flying below 60 metres (around 196 feet). In fact the restriction is 30 metres within the aerodrome traffic zone of a notified aerodrome during the notified operating hours of that aerodrome (article 86.2b (iv).

Getting permission from the CAA is not an impossible task however. Permission has to be sought for each site, giving at least 28 days notice, but permission can be granted for periods up to six months.

You can ignore the other restrictions unless you are in the habit of dropping articles from your rig (articles 58 and 87) or endangering the safety of persons or property (article 64) or are subject to a ban on flying by the Secretary of State (articles 85 and 118). Note that kites weighing less than 2kg are exempt from article 84. This refers to another Statutory Instrument, the Rules of the Air (SI 1996/1393).

Article 104 imposes restrictions on aerial photography on aircraft which are registered outside the UK. By implication, the order imposes no such restrictions on aerial photography on aircraft registered within the UK.

The Civil Aviation Authority, which is empowered to regulate all civil flying activities over the United Kingdom, provides a Guide to Safe Flying for Model Aircraft in document CAP 658 which lays down guidelines for where, when and how model aircraft may be flown. Interestingly, it turns out that if your model weighs more than 7Kg (15 lbs or so) then you must ask the CAA for permission to do aerial work – that is receive remuneration for flying activities. The rule specifically includes aerial photography.

However this document specifically excludes balloons and kites from the rules it lays down (see Definition of a Small Aircraft – paragraph 1 of Chapter 2).

Statutory Instrument 1987 No. 776, the Wireless Telegraphy (Exemption) (Amendment) (Model Control Apparatus) Regulations 1987, is the piece of legislation defining the various frequency bands allocated for “model control” in the UK. It defines four frequency bands for “model control” as follows:

1 26.96 MHz to 27.28 MHz
2 458.5 MHz to 459.5 MHz
3 34.995 MHz to 35.255 MHz
4 40.665 MHz to 40.955 MHz

Bands 1 (27MHz) and 2 (459MHz) are defined for general “model control”.

Band 3 (35MHz) is restricted to: model control equipment which is capable of being used solely for the purpose of controlling the movement of model aircraft

Band 4 (40MHz) is restricted to: model control equipment which is capable of being used solely for the purpose of controlling the movement of models on land or on water surface, and whose design employs exclusively the use of frequency modulation techniques

In addition the 433MHz band has been allocated for download telemetry from model aircraft.

This Statutory Instrument does not define ‘model aircraft’. However it is an amendment to the earlier Wireless Telegraphy (Exemption) Regulations 1980 (S.I. 1980/1848), which defines “model control equipment” as: wireless telegraphy apparatus designed or adapted for the purpose of controlling (otherwise than by means of telephony) the movement of a model vehicle, vessel or aircraft or a model of any other type by means of the emission of electro-magnetic energy from that apparatus and the reception of such energy by receiving apparatus in the model It’s clear that the equipment used for R/C KAPping is designed for the purpose of controlling … the movement of … , though it might be a stretch to describe a KAP cradle as a model.

OFCOM (which replaced the earlier Radiocommunications Agency as the appropriate regulatory authority), issues Information Sheets on these matters. RA 60 covers “radio-controlled models” and provides a useful summary.

The documents mentioned above are all currently available on-line:

Air Navigation Order 2000 (SI 2000/1562)

CAA Guide to Safe Flying for Model Aircraft (CAP 658) (A PDF Document)

Wireless Telegraphy (Exemption) (Amendment) (Model Control Apparatus) Regulations 1987 (SI 1987/776)

Wireless Telegraphy (Exemption) Regulations 1980 (SI 1980/1848). Note that this is not available from the HMSO website, but it is available from the Jersey (Channel Islands) legal site.

OFCOM RA 60

See also The UK Radio Control Council’s website which has frequency tables for many countries, including the UK, most of Europe and the USA.

Appendix 3

Radio-Controlled Models

1. Introduction

This information sheet serves two purposes. Firstly, for those who are new to the use of radio for controlling models it answers the basic questions about the frequencies and technical restrictions that apply. Secondly, for existing users it explains the additional frequency bands that have been made available for radio controlled models because of interference problems in the 27 MHz bands.

2. What are radio-controlled models?

Radio controlled models are of two types – :

      • those that operate on the ground or on water, known as “surface” models; and
      • those that are airborne.

Typically, radio control is used for model cars, ships (including steam, motor vessels and yachts) and aircraft. Radio-controlled models are often entered into competition, and the frequencies that are now available will facilitate their operation in European competitions.

This information sheet is directed towards the serious use of radio-controlled models. Toy radio-controlled models tend to operate at 49 MHz, where a small band exists for general-purpose low-power radio devices. Technical details of this band can be obtained from the Radiocommunications Agency – see Section 10.

3. Do I need a licence to operate model control equipment?

No. Model control equipment was exempted from the licensing requirements of the Wireless Telegraphy Act 1949 on 11 January 1981. The current regulations are contained in the Wireless Telegraphy (Exemption) Regulations 2003 (S.I. 2003 No. 74). Copies are available from any Stationery Office Bookshop.

Although licences are not required, equipment must still meet the technical conditions set out in the Regulations – see Section 6.

4. What frequencies are available?

The frequency bands available for the use of radio controlled models are shown below, with the maximum effective radiated power output of the transmitter measured in milliwatts.

Frequency
(MHz)
Use Effective radiated power (mW)
26.96 to 27.28 General

100

34.945 to 35.305 Air

100

40.66 to 41.00 Surface

100

458.5 to 459.5 General

100

The 26/27 MHz band is also allocated for Citizens’ Band (CB)radio and for low-power telemetry and telecommand devices, as well as for model control – see Section 7.

The 458/459 MHz band is also allocated to general telemetry and telecommand devices between 458.5 – and 458.95 MHz, and to specialised telemetry between 458.95 – and 459.1 MHz. While the potential for mutual interference is minimal, model controllers should avoid the specialised telemetry part of this band.

The use of the different bands is important. The 40 MHz band is dedicated solely to surface modelling. It consists of 34 channels with a 10 kHz channel spacing; the centre frequency of the first channel is 40.665 MHz. The 35 MHz is dedicated solely to aeronautical modelling. It consists of 36 channels with a 10 kHz channel spacing; the centre frequency of the first channel is 34.950 MHz.

5. Can I transmit data from the model?

Yes. Telemetry can be transmitted from general, surface or air models back to the controller. The band is 433.050 to 434.790 MHz; the maximum channel spacing is 25 kHz and the maximum radiated power is 10 mW. Please note that the band is not exclusive to model controllers – it is shared with other users, who are permitted to radiate relatively higher powers, so you must take care when selecting a channel for use in a particular locality.

6. What technical conditions do I have to observe?

Firstly, all model control equipment must operate within the frequency bands shown above. Secondly, the effective radiated power of the equipment must not exceed that shown alongside the frequency band in the table above.

These technical conditions are laid down in the Regulations, which have exempted model control from licensing. The Regulations also contain other conditions; most importantly, model control equipment must not cause undue interference to other wireless telegraphy equipment.

In addition, the organising bodies for the various sections of the model control hobby have established Codes of Practice and preferred band plans, designed to ensure the successful operation of models. Details are available from the UK Radio Control Council – see Section 9. In particular, to ensure safe operation it is necessary that no two modellers in the same area try to use the same frequency at the same time.

7. Interference in the 27 MHz band?

The 26.965 to 27.405 MHz band is allocated for CB radio, in accordance with a Recommendation put forward by the Conference of European Posts and Telecommunications Administrations (CEPT). The 27 MHz band is still available for model control but interference may be suffered from the other users of the band.

Within the model control band, there are five 10 kHz-wide channels that are used by low-power telemetry and telecommand devices but are not operational channels for CB. These have centre frequencies of 26.995, 27.045, 27.095, 27.145 and 27.195 MHz. While these channels may also suffer from interference, they should provide the best operating frequencies for model control within the new 27 MHz band.

In view of the problems associated with the 27 MHz band, frequency bands were made available at 35 and 40 MHz for model control. Just as CEPT CB was introduced on new frequencies to allow European harmonisation, the release of the frequencies at 35 and 40 MHz has brought the UK into line with other European administrations.

8. Is 35 MHz just for aeronautical modelling?

Yes. The Exemption Regulations make it clear that the channels at 35 MHz are solely for aeronautical modelling. Surface modellers must not use these channels. Similarly, aeronautical modellers must not use the allocation at 40 MHz, as this is reserved for surface modelling.

9. What is the UK Radio Control Council?

The UKRCC consists of representatives of all aspects of the model control hobby. It meets the Agency from time-to-time to discuss model control interests. It was from consultations in this forum that new frequencies were made available. Further information about the UKRCC may be obtained from:

Mr. D. W. McQue
The Secretary
UK Radio Control Council
6 Laburnum Grove
Bletchley
Milton Keynes MK2 2JW.

Tel: 01908 378277

E-mail: g4nju@aol.com
W ebsite: www.ukrcc.org

10. Further information

Enquiries about information given in this information sheet should be addressed to:

Science and Technology Unit
Radiocommunications Agency
Wyndham House
189 Marsh Wall
London E14 9SX

Tel: 020 7211 0153

Fax: 020 7211 0162

RA 60 (Rev 8)
February 2003

About billboyheritagesurvey

Heritage worker
Gallery | This entry was posted in KAP and tagged , , , , , . Bookmark the permalink.

8 Responses to Notes on KAP

  1. Heather says:

    Thanks for taking time in order to write “Notes on KAP | Billboyheritagesurvey’s Blog”. Many thanks once more ,Abraham

  2. Sheila Harvey says:

    I wonder if you would give me permission to use your ariel photograph of Warham Camp in an essay I am writing for a Cambridge University Diploma in Archaeology. The image will not be published to the public and in practice will only be seen by myself and my tutor. I am particularly interested in your image because as you point out, it shows an indication of the earlier course of the River Stiffkey.

  3. Very useful article, thanks. Maybe http://airhes.com would be interesting for you as a new application for kites and new global resource of fresh water.

  4. Andrei,

    As I understand it the system collects and condenses water vapour from the atmosphere and uses it to turn a turnine on the ground. For this to be effective the kite will have to suppport a great weight of clooected water, am I correct?

    For useful quatities of power this neeeds to be a very large collector flown at a great height.

    Other methods of using kites for power generation are airborne wind turbines and even line hauled ground generators.

    B

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s