Descr geography new.db
For the RTW file see: descr_geography.db
Editing descr_geography_new.db with IWTE
Open the .db file by using the Veg/GeogDB tab and Read/edit geography.db button. When you've finished making all your changes use OK-write files to save. The new files will be written with _IWTE or _1 added to the end to avoid accidental overwrites of your original files - change the names of the new files to allow them to be used in game.
Select the required Climate and Season and Ground_Textures. Double click the texture name you want to change to open the line for editing.
The underlined BGR values in the picture make up the colour which the game uses for distant bits of landscape which would have used that battlefield texture. If you're drastically changing a texture colour (e.g. from grass to snow colours) you will want to change the BGR values too. NOTE: If you have a geography_new.db that was created by letting M2TW regenerate from the text file ALL of the BGR values will have been wiped out and re-set to 0 0 0! This is why some mods have ended up with black distant mountains.
Copy Climate Function
If you wish to copy all of one Climate's Season to another use the Copy Function tab. Select the From and To Climates/Seasons as required and toggle the settings you want to copy. If you don't know what you're doing, you probably want to toggle all of the settings to ON!
Click 'Copy selected data' - you will need to use "OK - write files" to save a file with the copied data.
If you open the Vegetation.db at the same time you can also copy the Vegetation Groups within that db as part of the same process.