This is a rectified montage of the gun deck pavement of Martello tower 24. It was achieved by 4m PAP (Pole Aerial Photography) on the 3rd visit to site. It’s a stitch of 9 images rectified in PhoToPlan and then balanced and feathered in Photoshop.

Control for the rectification was by REDM to detail points collected in TheoLt:

In this plan I plotted the wall top from intersection in PhoToPlan 3D, orientated to the same control points from our reconaisance KAP imagery, an example of which is here:http://www.flickr.com/photos/bblakecambridge/5164832971/

The orientation results weren’t great because of the distribution of the points but I had 2 images that worked just well enough to get the egg shape for the plan here’s one:

KAP let us down for the pavement survey despite probably being the easy way to get the photo-cover required in a single shot. The wind just wasn’t kind enough and the best place to fly was in the hands of a civils firm fighting the rising sea-level with a new mass concrete sea wall. A shot of the tower taken from a 2.7m Sutton flowform kite. On the day ( we had a 4 day window with the gun off the tower before works began!)  it’s as close as we could get without access to the sea-front. To get the pavement we used the KAP rig on the PAP pole with the same RC and video link. This tower is impressively armed with a mighty 25pdr:

we had to wait until it was lifted before we could record the pavement condition in advance of works to stop the leaking, visit when it rains and you get wet!

Once the pole is set up and the rig hoisted ( this takes a bit of courage, I hate seeing my camera waggling around hanging off a gallows bracket…give me a kite line any day) it’s a case of working as quickly as possible to get even illumination across the whole photo block…and taking advantage of rare moments of excitement like the bit where we have to negotiate the flag pole.

Surprisingly PAP requires a light weight set up very similar to KAP so all the experience gained with getting the weight down paid off but without the fun of flying a kite!

In this case the pole was angled out over the subject making the load for the pole’ dancer’ pretty tough, 4m was do-able; 5m required 2 people on the pole and generated a lot of movement at the camera. Here is the team in action -we spent the whole job staring at our feet..and still managed to get quite a few shots with feet in: Many thanks to the patience of all involved in getting the project done, particularly David Andrews and Clive Hollins.  Reconnaissance photography of the pavement with the LeicaX1 was poor as the auto-focus and aperture settings failed to get sharp cover, the low light performance of the Olympus EP1 did the trick. Just as we got to the end of our sweep the sun came out and we were able to fly over the next tower in the chain, just to confirm KAP cover would be ideal if we had the chance:


More on PhoToPlan 3D here: http://theolt.wordpress.com/category/photoplan/ and a neat video : http://download.kubit.de/english/videos/PhoToPlan/PhoToPlan_3D.mp4

About billboyheritagesurvey

Heritage worker
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