'Twas only yesterday that I found out that the map layout data in HeartGold and SoulSilver is in a/0/6/5 when extracting it with a tool such as DSBuff, Nitro Explorer, Tinke or even CrystalTile2.
And there definitely is something I still need to learn... and that is how the polygons operate in the hex values.
I'm still looking forward to the map editor, just remember everyone... the more things you post about what you've noticed during your research in the ROMs, the more progress the developer will have.
If there's anyone wants to know where the locations of the map layout data in Tinke or CrystalTile2... well here they are:
Diamond/Pearl/Platinum: fielddata/land_data/land_data.narc
HeartGold/SoulSilver: a/0/6/5
Black/White: a/0/0/8
Instead of trying to mess up the map layout data, I'm gonna start messing around with the map_matrix.narc file in Pokémon Platinum. When I see the expected results, I shall post it here. ;)
Edit: I've just noticed that the map_matrix.narc has the same names as the BMD0 and MDL0 files. So I assume map_matrix.narc could be where the names are given for the models (which are buildings, houses ect). Like how the mapname.bin file works, it might have connection to the map_matrix.narc file.
Edit 2: Well, looks like I've found the weather pattern texture for Eterna Forest, which is shown in the screenshot. The mystery of the data for using the different weather effects remains. Ah well, more research is needed to be done, but either way... every research counts as improvement towards new things.