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-Relative 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
spymicmac.micmac.mosaic_micmac_tiles()
(or mosaic_micmac_tiles) depending on
how large they are:
mosaic_micmac_tiles Orthophotomosaic -imgdir Ortho-MEC-Relative
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.