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Topics - bravemaster3

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General / DJI Phantom 4 multispectral in non ideal conditions
« on: January 28, 2023, 05:19:51 AM »
Hello everyone,

I have read through all discussions and tried all kind of things, and finally thought of posting a question.
I have a bunch of DJI Phantom 4 multispectral (DJI P4M) images to process, and despite following the articles from Agisoft and other platform on how to best process them, I am having the problems pointed out by others, like in this discussion:
Maybe it is not the same kind of problem, but here is the thing:
I know I did not fly under ideal conditions, and had some direct sunlight in some images on a cloudy day.
However, I believe there is a problem in the way Agisoft uses reflectance panel values for calibration of DJI P4M maybe?
I am saying this because the orthophoto looks good with Sun correction only, but I get the image in attachment when I use a 20% spectralon panel. Note, the choice of that panel was made after plotting Sun sensor corrected values of 5%, 20%, 50% and 99% with their real values, and noticing that there is a ~linear relationship (measured vs actual reflectance) which curves into more exponential between 20 and 50% and above.

Anyway, the reason why I am suspecting a problem in the way Agisoft does the integration of a reflectance panel is double: Apart from what I mentioned earlier that the results are good without panel, I also tried to export sun corrected images from Agisoft and do reflectance panel correction per chunk myself in python and then run the rest of the processing in Opendronemap, and the result was good (unfortunately it is not a viable option for me as it takes long time and needs a lot of resources as I have a lot of missions to process).

I wanted to do the same (i.e. process those images that were panel-corrected by myself in agisoft but then I get a strangely quick processing, with mostly gaps in the orthomosaic).

Did anyone get very good well balanced orthomosaic in Agisoft despite having flown in non-ideal conditions using DJI P4M? If yes, any advice will be appreciated!

Thank you.

It is not a matter of panel. With or without panel, the problem is the same.

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