I had trouble using the MGM because my pc ran out of memory (happens if I have subpix 3 and a correlation kernel size smaller than 9.)
It works with subpix 2 and corr kernel size, 5, 7 and 9 if i set the threads to 4 (I am running locally on a mac) :) I do indeed get a more smooth surface without the squares. However, it created some new questions.
1. Is there a 'standard' stereo.default file example for MGM and SGM I can use? If I do not specify a file and simply run: 'parallel_stereo left.cub right.cub --stereo-algorithm asp_bm /resultFolderMGM' then it somehow finds the stereo.default file on my system and when I check the stereo.default in the debug it has asp_bm selected.
2. Related to the first question, I have made my own stereo.default file consisting of:
alignment-method local_epipolar
stereo-algorithm asp_mgm
corr-kernel 5 5
cost-mode 4
median-filter-size 3
subpixel-mode 2
subpix-from-blend
skip-point-cloud-center-comp
corr-seed-mode 1
sgm-collar-size 0
threads 4
But is the MGM solution rectified the same way as in the BM solution? I see in the documentation that I should set the 'alignment-method local_epipolar' when running MGM but the BM default.stereo has NONE , EPIPOLAR, HOMOGRAPHY and AFFINEEPIPOLAR. Should MGM still have one of these?
3. It says in most of the documentation that the MGM and SGM produces higher quality results than BM. What is that based on? Visual inspection or is there another parameter? I notice that the triangulation error remains the same regardless of if I use BM or MGM and that the MGM geotiff is less dense (as if it is "just" smoother). When I compare the BM 'standard' (using the standard settings from stereo.default) with MGM using the above parameters in (2.) and geodiff I get the attached map with differences of more than 100 m which seems to not be related to the squares. Is there any argument for trusting one model over the other?
Sorry for all my questions, I am very grateful that you are taking the time to answer.
best,
Christina