I'm looking for a website or company that either sells or has free terrain data maps. The USGS (United States Geological Survey) does not seem to have any, or I cannot navigate their site well enough to find them.
This is all for a voxel engine that I've been tinkering around with. Scale of the map does not matter because I can smooth out the large changes in height through bi-linear interpolation, altering the cell size of the world, and by producing noise in the height data.
I have spent weeks and months trying to find terrain maps to no avail. NASA site is large and has plenty of photos but I could not find any useful maps, especially ones that I could download legally.