L1D-20c image quality: 1st thoughts

This is not definitive, so far I have only used this camera on the default ‘auto’ settings but I want to get a start on this, if nothing else to set a datum for what, hopefully follows.

The L1D-20c is produced by Hasselblad for DJI and is mounted in the DJI Mavic pro 2 multirotor UAS. As a PfCO student I’m in the process of logging some flight time to develop procedures prior, hopefully to CAA approval. I’m no stranger to low level aerial photography but a fully mobile, unrestricted  3D environment is a novelty for the kite flier.

First results are encouraging, as well as enjoying the new ceiling of 120m (over the 60m for kites) the mobility is something of a thrill- where KAP takes a lot of patience and a fair bit of planning around the weather DAP is different and the wind consideration is oposite: low or zero windspeed is preferred.

The camera is widely described as a 1″ CMOS sensor : it is 13.2mm x 8.8mm, focal length is 10.3mm. The 20mpx frame is 5427 x 3648px.

At 120m AGL the cover is 154 x 103m thus:

Hasselblad-frame-cover-at-120mAGL-2

L1D-20c_GSD_01

At 100% pixel size the DoF at f4 copes with the 68m high foreground object at 1/120 s, 100 ISO:

Pixel-size-1

Let’s take a look away from the image centre:

Hasselblad-frame-blow-up-cover-at-120mAGL-2

GSD is 2.81 cm/px and a 100% blow up of the frame edge shows the limit of resolution at f4:

Punto-3

This may not be an optimum exposure as sharp focus from 50m to 120m at f4 stop is optimistic. This frame (and the entire block) were over exposed by something like 2 stops (shown post adjustment here) so manual exposure control will prove the performance at the tighter stops.

DJI_0091

Making use of the permissions I have I flew a photogrammetric swath of 122 frames (and drained the battery in around 25 minutes) to produce a 240m x 220m ortho image:

MVP2_Earith_Ortho_crop_02.jpg

At 100% it looks like this:

Earith-px-at-100pc-1.jpg

The mix of the new ceiling and smaller sensor (I use APSC and full frame at 60m AGL for KAP) reduce resolution somewhat but the utility of the Mavic Pro2 cannot be denied.

For me this is a big step, I have committed heavily to KAP for its joy, beauty and simplicity I have learned a lot and continue to do so: as a slave to KAP IQ I have flown bigger and heavier cameras then I could ever have imagined and spent hours making it work. You get to appreciate the value of the viewpoint when you depend on the wind.

I have flown cameras from balloons, swung them from poles and now a fully functional flying high res camera is available for DSLR money- it’s a gift of the age we live in and I accept. In learning its ways I have come to respect the interlinked systems that allow me the privilege of the view point, it’s not as personal as KAP but none the less a privilege to be able to capture the world from above.

B

About billboyheritagesurvey

Heritage worker
Gallery | This entry was posted in Landscape, Significance, Survey Practice and tagged , , , , . Bookmark the permalink.

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