computing the relative orthophoto

Once you have the relative orientation, you can use Malt to compute a relative DEM and orthoimages:

mm3d Malt Ortho "OIS.*tif" Relative DirMEC=MEC-Relative NbVI=2 MasqImGlob=filtre.tif ZoomF=8 DefCor=0 CostTrans=1 EZA=1

This will run Malt on all of the images, using the orientation described in Ori-Relative. Malt defaults to only running where 3 or more images are visible (NbVI=3), but it is usually fine to go with 2 images. At this stage, we don’t need the DEM to be processed to full resolution - a lower-resolution version (ZoomF=4 or ZoomF=8) will suffice. The EZA=1 argument ensures that the values in the DEM are in the correct units.

Once this command finishes, you will have two new directories: MEC-Relative and Ortho-MEC-Relative. The DEM and associated correlation masks are found in MEC-Relative, while the orthophotos are found in Ortho-MEC-Relative.

creating the orthomosaic using Tawny

Note that the orthoimages are not mosaicked - they are just the individual images orthorectified using the extracted DEM. To generate an orthomosaic, we use Tawny:

mm3d Tawny Ortho-MEC-Malt Out=Orthophotomosaic.tif RadiomEgal=0

Here, we use RadiomEgal=0 to use the images as-is, rather than attempting to balance the radiometry (as this can lead to undesirable results). Finally, you might need to re-combine the image tiles using mosaic_micmac_tiles.py, depending on how large they are:

cd Ortho-MEC-Malt
mosaic_micmac_tiles.py -filename Orthophotomosaic

Once this is complete, you can move on to the next step: registering the orthoimage and automatically finding control points using an external DEM and satellite image.