Panzer Campaigns - explain graphic files

[BigDuke66]

Hi
is anyone able to explain what row depict what ingame terrain for the files:
2DFeatures100.bmp
2DFeatures50.bmp
2DHexSides100.bmp
2DHexSides50.bmp
I ask because afaik the files are similar to those of Panzer Battles but there is much less different terrain types in PC compared to PB so a lot rows seem to be unused.
Some terrain is obviously but it seems that in some combination different terrain is used, for example for forest one of the other rows seems to be used of there is any kind of road/rail passing through that hex.

So is anyone able to explain what row is when used?
Or is there any documentation for it?
Would be very valuable for designing graphic mods.