The gta.data is a data text file, of the game.
This file lists which files define the game map.
It can be opened and edited with any text editor.
To comment put # before what you are going to write.
The file is loaded when the game starts.
Then all the files names in it are loaded shortly after.
Each line links to a map file, unless it's commented out, or
nothing there. Most entries use the following format, which is, in general, very simple:
The file is not split up into any selections, but,
entries are usually grouped by type and arranged in a special order according to the game's loading sequence,
as the file, comments state:
1. Archives (IMG)
2. Item Definitions (IDE)
3. Collision Files (COLLISION)
4. Map Areas (MAPZONE, IPL)
5. Item Placements (IPL)
These entries define additionally used IMG archives (other than the hardcoded loaded ones).
You can only define a maximum of five entries. Any more will crash the game.
These keywords are used to link to IPL-style item placement and zone files.
These define the splash screens that appear while loading the map.
Some mods which come with a new gta.dat, for some users
crash, the reasons may be the following two:
1: Installation of the mod was not done correct.
2: The folder in which is a entry in the gta.dat pointing too, does not exist.
In GTA 4, there exist water, and an IMGlist part.
As stated above, the first part of the gta.dat
You may add 2 more max entry's for you're new file. Any more than this will crash the game.
Also you should make sure you put them in the correct order; load IDE's first, then the models and after that the IPL's.