I am beginning to use the --dsm option as I would like to superimpose the dsm with my orthophoto.
I order to obtain the same size of pictures I pass the --dem-resolution with the same value as the --orthophoto-resolution but I observe that the dsm as a lower size than the orthophoto.
Only mitigation I have found so far is to use the --ignore-gsd.
Is this normal ? Is there another way to achieve my purpose because this way it de-caps the ortho resolution which is not my point.
I think the ortho will always be twice the size of the DEM, but you could rescale one or the other afterwards.
[INFO] Running odm_dem stage
[WARNING] Maximum resolution set to 2.0 * (GSD - 10.0%) (1.62 cm / pixel, requested resolution was 1.00 cm / pixel)
Creating output file that is 11036P x 12463L.
and
[INFO] Running odm_orthophoto stage
[WARNING] Maximum resolution set to 1.0 * (GSD - 10.0%) (0.81 cm / pixel, requested resolution was 0.70 cm / pixel)
I believe the historical reason is that realistically, the vertical data is somewhere on the order of 1/4 to 1/2 the accuracy of the horizontal data, so we cap the DEM resolution to keep it subsampled a bit to smooth things out.
If I recall correctly, we raised it from 1/4th to 1/2 earlier last year in response to the proliferation of better GPS units in sUAS and ground units.
The reason for the cap is about the limitations of depthmap calculations in the face of a noise ceiling (floor?). If you want depth information for every pixel, you will significantly increase your noise without introducing more information.
Now, OpenMVS has improved its depthmap calculations substantially in the last few weeks, months, and years, so far it may be feasible to get good results at GSD. It’s certainly worth testing.
