SOURCEMP.DAT
This file is only used by tactical saves.
Length of file is map size (overall number of tiles) + some 4 bytes at the end.
File contains data about light from mobile sources (soldiers, flares). It is recalculated every time a unit moves. Together with TERMP.DAT it is full info about current lighting of the map. Actual lighting of tile is lower value from both files. Exact meaning of values is a number that pallette is shifted towards darker colours.