How to color dense cloud by reflectance?

[luckycharms]

Hi all,

I'm using Metashape 1.5 Pro with a Micasense Rededge-M to build point clouds and orthomosaics.  I want to have these point clouds and orthomosaics to be colored by reflectance, not just "color" (i.e. radiance).  Is there some way to do this?  Or, is there a way to verify that the colors are indeed reflectance and not radiance, if that is supposed to be what is produced?

Thanks!

[Alexey Pasumansky]

Hello luckycharms,

Have you tried to apply the raster transformation that is mentioned in section 11 of the following instruction:
https://agisoft.freshdesk.com/support/solutions/articles/31000148780-micasense-rededge-mx-processing-workflow-including-reflectance-calibration-in-agisoft-metashape-pro

[luckycharms]

Thanks Alexey.  Yes, I can export ortomoasics as you mention.  I don't see how to do this for point clouds however.  Also, can you confirm that colors in pointclouds are actually reflectance and not radiance/"DN" values?

[Alexey Pasumansky]

Hello luckycharms,

If you use calibrate reflectance prior to the dense cloud generation and then build dense cloud with "point colors" option enabled, then you would be able to export the reflectance values (with the help of normalization via raster transform dialog). The requirements:
- perform the reflectance calibration operation,
- apply normalization to 0 - 1 range in the Raster Calculator dialog (like on the previously posted screenshot),
- use XYZ point cloud export format,
- enable "Point Colors" option in the Export Points dialog,
- disable "Convert to 8-bit RGB" option in the Export Points dialog,
- select "Index Value" option in the Raster Transform section of the Export Points dialog.

The resulting text file will have 8 columns: XYZ coordinates and five columns related to the "color" information, which would be reflectance after the applied normalization. For example:

Code: [Select]

25.952836 24.241329 253.175663 0.022522 0.067780 0.027863 0.148193 0.581757
25.952829 24.241306 253.033232 0.022369 0.067322 0.027405 0.143707 0.615845
25.952849 24.241259 253.137510 0.023407 0.071472 0.030243 0.152832 0.560822
25.952854 24.241280 253.105739 0.023071 0.070404 0.030334 0.153748 0.567566
25.952859 24.241302 253.234556 0.022339 0.067017 0.027863 0.143890 0.592896
25.952866 24.241325 253.221900 0.022583 0.070129 0.028748 0.150208 0.573364
25.952890 24.241299 253.125706 0.022888 0.068054 0.029388 0.146820 0.568787
25.952883 24.241276 253.138363 0.022858 0.069336 0.030273 0.150391 0.566772
25.952913 24.241272 253.184602 0.022064 0.066284 0.027771 0.145020 0.584045
25.952919 24.241293 253.152832 0.023254 0.071198 0.031372 0.152618 0.558960

[luckycharms]

fantastic, thank you.