

The numbers are often stored in an image format as a grayscale. World heightmaps from USGSĪll heightmaps files are an array of numbers. hgt format which can be opened with QGIS. He has his improved DEMs available from Viewfinder Panoramas. Jonathan de Ferranti has spent a lot of time improving DEMs from NASA's Shuttle Radar Topography Mission (SRTM) and other sources. World heightmaps from NASA - improved by Jonathan de Ferranti

They supply these as a series of tiles which you can join together in QGIS. This allows commercial use, with acknowledgement. The heightmap in Tutorial: Make mountains in Blender from height maps was created by the University of Otago - National School of Surveying who have published it at Koordinates, and is released under a Creative Commons Attribution-Share Alike 3.0 license.Both websites allow you to choose the map projection. You can download several at once, you can also crop an area of interest which saves on download time.

These websites know heightmaps as Data Elevation Models (DEMs).

They have maps of all of New Zealand in GeoTIFF and ASCII formats, which can be opened with QGIS. Koordinates and Landcare Research are two sources for heightmaps. It is written from the point of view of someone wanting to use them for modelling terrain in Blender, but it is relevant to modelling with other 3d packages. This tutorial provides heightmaps, links to them, and talks about what to look for.
