Thx patrik for the nice list.
some questions/remarks:
Elevation; i concluded 1byte size from the legends export height map, since it's greyscale. seems DF is compressing that already in legends mode
Rainfall, Vegetation, Drainage, Salinity, Savagery, Evilness and Volcanism: I need those in a much lower granularity (if i need them)
Trees: i'll store these in a seperate list, needs to be seperated from the heightmap anyway for efficient display, and probably i wont care about the upper levels of the trees, except maybe the final height of the tree
Tile material: A must, but maybe it can be compressed with a rle compression, need to look at actual data first
Critters, items, smoke and contaminants: as i understand mifki, the whole worldmap is only accessible on embark screen, so i don't know if they are available at that point, will try out when i come home from work
Another thing i need to check is if DF can be read fast enough to get a (somewhat cached/read ahead) 'live' readout while in embark.
I don't aim (yet?) for a ingame mode like armok's vision, a still map is quite enough for me
@mifki (if you're reading this): Do you remember how long it took to read the data out of DF for your bigmap?
)