Free data sources

There are many free datasets available, but there are only some few with world wide (or almost world wide) coverage.

ASTER-GDEM
Check how free this really is!

Shuttle Radar Topography Mission (SRTM)
Elevation data for all land masses between the 60th degrees of latitude on a 3 ArcSec (90m) grid. This is the first choice for elevation data. However, in some mountain regions there are remarkable data holes. The complete data set is about 9 GB bz2-ziped and probably between 30 and 40 GB unziped.

GTOPO30 / SRTM30
GTOPO30 is a world wide elevation data set for all landmasses, even above 60 degrees of latitude. It's resolution is 30 ArsSec, thus by factor 10 lower than SRTM. SRTM30 is an improvement of GTOPO30, basing on SRTM data.

This is the second best elevation data source freely available in interesting for polar regions and regions with large holes in the SRTM3 data set.

ETOPO2
A world wide set of elevation and water depth data with 2 ArcMin resolution, thus by factor 40 lower than SRTM3. Interesting only for ocean depths.

SRTM Water Body Data (SWBD)
Coastlines, broad (>180m) rivers and lakes with 1 ArcSec resolution, based on SRTM data. Available from the same source.

NOAA High Resolution Hirarchical Shore Lines
World wide shoreline data, somewhat lower resolution than SWBD, but not limited to the rnage between the 60th degrees of latitude. There are also lakes included, but the data is derived from the WDBII and has quite a low resolution.

VMAP0 water bodies
Rivers and lakes world wide with a fairly usable resolution (2km). The best available data for smaller (<180m) rivers and rivers and lakes above the 60th degrees.

VMAP0
Best free source for world wide road and railway data. However, only usable for scales down to 1:500,000

GADM
http://biogeo.berkeley.edu/gadm/ - looks promissing.

Maplibrary
http://www.maplibrary.org/ - looks promissing.

World DataBase II (WDBII)
Somewhat outdated political borders with low resolution.

VMAP0
VMAP0 also provides political border data, but they are not free for commercial use and thus incompatible with our license.