Phantom4 MS - orthomosaic reflectances

ODM
1

Hey ODM community!
I want to compute NDVI and other spectral indices from Phantom 4 Multispectral flights.
What would be the optimal ODM processing settings to obtain valid reflectances (in the range of 0-1) values? I’d appreciate some guidance! At a loss with so many processing options - first time using drone imagery! Pixel values in the bands of the orthomosaic include negative values and other very small ones (like commented in this thread: Multispectral orthomosaic reflectance values). Details on processing options and bands statistics below.
Thanks in advance for your advice and processing tips! Cheers!

For the record, I have also tried --radiometric-calibration camera+sun, but then I get this message: ===== Done, human-readable information to follow… =====

[ERROR] Uh oh! Processing stopped because of strange values in the reconstruction. This is often a sign that the input data has some issues or the software cannot deal with it. Have you followed best practices for data acquisition? See Flying Tips — OpenDroneMap 3.5.4 documentation
100 - done.
ERROR: LoadError: failed process: Process(docker run --rm -v /Users/ODM_jl/2023-10-31_plot_3_60mts:/dataset opendronemap/odm /dataset --min-num-features 24000 --orthophoto-resolution 1 --dem-resolution 1 --radiometric-calibration camera+sun --texturing-skip-global-seam-leveling --orthophoto-no-tiled --orthophoto-compression DEFLATE --skip-3dmodel --use-exif, ProcessExited(1)) [1]15:42

Band stats are:
Band 1 * STATISTICS_APPROXIMATE=YES

  • STATISTICS_MAXIMUM=0.00034588208654895

  • STATISTICS_MEAN=4.1638241700016e-05

  • STATISTICS_MINIMUM=0

  • STATISTICS_STDDEV=3.9477168852232e-05

  • STATISTICS_VALID_PERCENT=100

  • Scale: 1

  • Offset: 0
    Band 2 * STATISTICS_APPROXIMATE=YES

  • STATISTICS_MAXIMUM=0.00023238248832058

  • STATISTICS_MEAN=4.305794611104e-05

  • STATISTICS_MINIMUM=0

  • STATISTICS_STDDEV=3.0363897633484e-05

  • STATISTICS_VALID_PERCENT=100

  • Scale: 1

  • Offset: 0
    Band 3 * STATISTICS_APPROXIMATE=YES

  • STATISTICS_MAXIMUM=9.4602539320476e-05

  • STATISTICS_MEAN=1.9053275863524e-05

  • STATISTICS_MINIMUM=0

  • STATISTICS_STDDEV=1.234490200541e-05

  • STATISTICS_VALID_PERCENT=100

  • Scale: 1

  • Offset: 0
    Band 4 * STATISTICS_APPROXIMATE=YES

  • STATISTICS_MAXIMUM=0.0004375149437692

  • STATISTICS_MEAN=9.3793929263158e-05

  • STATISTICS_MINIMUM=-3.2635998650221e-05

  • STATISTICS_STDDEV=6.0245358047185e-05

  • STATISTICS_VALID_PERCENT=100

  • Scale: 1

  • Offset: 0
    Band 5 * STATISTICS_APPROXIMATE=YES

  • STATISTICS_MAXIMUM=0.0004199493851047

  • STATISTICS_MEAN=8.9436464517462e-05

  • STATISTICS_MINIMUM=-4.1719085857039e-05

  • STATISTICS_STDDEV=5.8862251313409e-05

  • STATISTICS_VALID_PERCENT=100

  • Scale: 1

  • Offset: 0
    Band 6 * STATISTICS_APPROXIMATE=YES

  • STATISTICS_MAXIMUM=255

  • STATISTICS_MEAN=224.74428159194

  • STATISTICS_MINIMUM=0

  • STATISTICS_STDDEV=82.46089799208

  • STATISTICS_VALID_PERCENT=100

  • Scale: 1

  • Offset: 0

2

I personally use this command to create orthomosaics. I use ODM command line interface. I don’t know the recommended flags but I do know that radiometric calibration is a must for multispectral images and I use camera option. I believe that camera+sun option needs some sun panel images which is then used to normalize the images. Here’s my options

docker run -ti --rm -v ./1_Best_2024_10_01/:/1_Best_2024_10_01 opendronemap/odm --project-path /1_Best_2024_10_01 P4_MS --auto-boundary --orthophoto-resolution 2.5 --radiometric-calibration camera --orthophoto-compression NONE --optimize-disk-space --fast-orthophoto

One thing to clarify is that orthophoto-resolution is capped to GSD estimate, so I made it low

3

Thanks, Mend-Amar. I tried also your options and read lots of threads like Add support for P4 camera+sun calibration · Issue #1483 · OpenDroneMap/ODM · GitHub or P4 Multispectral Support by pierotofy · Pull Request #1513 · OpenDroneMap/ODM · GitHub but still didn’t find out why there are negative and very small values in the orthomosaic if the values are supposed to be reflectances. what range of pixel values do you obtain with your options for each band?