To go a little bit further than the semantic question regarding DEM/DTM/DSM, I'd like to know if there is a free (of charges and use) DTM datasets? And what about resolution?
As far as I know,only DSM are available to public for free.
[GIS] DTM available for free somewhere
datadem
Best Answer
For a list of sources, see also here: http://grass.osgeo.org/wiki/Global_datasets