Community 3.3.6

[Saul Kelly]

I have several DTM's I would like to use instead of processing one from scratch.

[Thomas Barucchi]

Hi Saul,

yes you can use an external DEM for orthorectification. Simply use the DEM Merging Tool.
The DEM merging tool can be accessed from the Tools menu and does not require any DEM to be loaded in the main window. It can merge files stored in different formats and horizontal resolutions.