I've not seen one written anywhere...

You could I suppose work one out - check descr_characters.txt to see what starting action points are set at. Decide who you think has just the starting points (I'd assume infantry unit without general, is probably on that, with bonus / restriction applied to cavalry / siege units)

Park that unit on bit of land you know to be just plain fertile ground_type (hills, woods and swamp all slow movement - roads speed up movement) and 'measure' the distance from unit to extent of its movement range using
show_cursorstat
in the console.

Each change in co-ordinate from show_cursorstat represents one pixel on map_regions.tga

It might turn out to be a one to one ratio - but as the movement gets varied by so much I never paid a lot of attention to how it related....
If you do look at it let us know