Descriptive text for maps showing geographic areas

I’m trying to provide examples of how to write descriptive text for maps. Specifically maps showing geographic areas coloured in different colours depending on species of animal/fish located in those land/sea areas. I have not seen the actual content from which these maps were generated, but I imagine that it consists of a lot of x,y coordinates which would not be of much use. I can’t seem to come up with any concrete examples on the web, most searches end up with “image map” which is not what I’m looking for. My favourite resource for graphic organizer descriptions is at National Center on Accessible Instructional Materials , but I can’t find any similar resource for geographical maps (which in this case are either jpg, gif or png image files, but not image maps).
Any pointers?

This sounds like a classic case for longdesc (although as no known user-interface ever figured out how to make that work, you’ll want to provide a regular link as well). You could then give a table of the data used to generate the map, listing countries/regions and the relevant text or numbers alongside.