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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.

Thanks, simo

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Where in the world do you need the information for? – James S Feb 3 '11 at 11:51
There's some sample lidar data here: – Kirk Kuykendall Feb 3 '11 at 17:43

For a list of sources, see also here:

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If you are in the UK there is the Ordnance Survey Land-Form PANORAMA dataset that is available as part of OS OpenData. It is available as a DTM or as contours. The DTM is designed for use at a scale of 1:50,000.

For more information, use the link below:

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Hi James. Thanks for that information. Unfortunately, I live in France and IGN did not yet release its DTM for free - the free release of the BD ALti is minimum 250 m resolution. It takes time, but they are on a good way ... – simo Feb 3 '11 at 18:08

Unsure of your location, but you may want to try the USGS if you're in the US. I think resolution is variable based on location, but you may find something of use here:

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It looks like the topo maps have been moved, if that is what you are looking for. But a search for them provided me with this link that might be helpful – MaryBeth Feb 3 '11 at 16:48

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