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Author Topic: Rolling shuter DJI MINI 2  (Read 451 times)

gantar1

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Rolling shuter DJI MINI 2
« on: May 10, 2021, 10:04:31 AM »
Hey,

i'm traying to build ortomosaic with photos of DJI MINI 2 with ground points. Result with option rolling shutter enabled is worse than if rolling shutter is disabled. Red and cyan lines are correct. What can be wrong?

Best regards,
Kristjan 
« Last Edit: May 10, 2021, 10:06:55 AM by gantar1 »

Paulo

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Re: Rolling shuter DJI MINI 2
« Reply #1 on: May 10, 2021, 12:22:52 PM »
Hi gantar1,

to check the accuracy of the two alignments, with or without rolling shutter, I would use some GCPs set as check points during optmizing process (assuming tou have at least 3 to use as control). This way  you will get an independant assessment of accuracy....

Comparing roof footprints against ortho will not do it especially if you did nor use a precise DSM for rectification (true ortho vs just DTM based ortho where roof outlines are not accurate)....
« Last Edit: May 10, 2021, 12:28:27 PM by Paulo »
Best Regards,

Paul Pelletier

gantar1

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Re: Rolling shuter DJI MINI 2
« Reply #2 on: May 11, 2021, 10:17:19 AM »
Thanks for reply, we have controls measured with GPS (Leica 1cm). with rolling shutter off it looks OK. In both cases are heights wrong (cca 1m difference). This problem is only on mini 2. With Phantom 4 V2 is everything OK.

Kristjan

Paulo

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Re: Rolling shuter DJI MINI 2
« Reply #3 on: May 11, 2021, 12:03:42 PM »
Kristjan,

maybe you can show  calibration page from report to see if there excessive are values for adjusted cx, cy relative sensor size or if f varies greatly from initial value (around 2785 pix). We have experienced some similar problems with DJI Mavc 2 Pro....
« Last Edit: May 11, 2021, 12:15:39 PM by Paulo »
Best Regards,

Paul Pelletier

gantar1

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Re: Rolling shuter DJI MINI 2
« Reply #4 on: May 11, 2021, 01:38:12 PM »
Hey,

here is report.


Paulo

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Re: Rolling shuter DJI MINI 2
« Reply #5 on: May 11, 2021, 03:52:47 PM »
Hi gantar1,

yes it seems the estimated value for f is quite off the starting value (4490 µm / 1.76 µm/pix = 2550 pix) and cy is about 33 % of half sensor height. This happens for Mavic 2 pro when flying with camera always pointing in same direcion regardless of turns. For example for N/S lines drone will first go forward to North in first line then backwards to South in 2nd line, etc...so top of camera will always face North...

I would try to do a new alignment  wth f, cx, cy, b1 and b2 fixed to see if you get better results...
« Last Edit: May 12, 2021, 06:02:57 AM by Paulo »
Best Regards,

Paul Pelletier