Grafik Viewer Programming Help needed!

[Romsstar]

I want to write a Map Viewer for a specific Game.
I figured out the Format the game uses so I know how to decompress the graphics.
And by analyzing code I found out that the maps are of course tiled.
Now in my Map Viewer I want to write I would of course want the Map to be displayed just as ingame,
so as whole and not in tiles..
For example align it in a grid or something...
But the question is where I can find the information how the tiles are aligned so that a picture results from it?
Shall I dissasemble the graphics loading process and look there for the information or should I dig in the Graphics File itself?

Since it is a PSX Game some information:

The graphics format for the MAPs itself is called *.TFS seems to be a custom format.
Well whatever for every TFS file there is also a corresponding *.MAP File.
They always continue a TIM file and also additional information which I can't understand though.
I don't know how to... With the TFS file it was easier since I could understand general image format and defaults
and also I knew how CLUTs look like.
but how to know what exactly those MAP Files store and how to gather the information there.
By corrupting the MAP files I found out that they seem at least to store the exits and entrances of a room but no idea where and how and how to figure out.

Some help would be appreciated I'm rather a beginner but I made progress and I would like to continue I just need some heads up or hints.
Thanks in advance, much appreciated.