How map system works?

[Temessis]

Hi, I want to write an external program for mapping (not inside a client), which creates my own map and layers using chunks from /Haven and Hearth/map folder. But I've got big problems with it, cause Haven's map downloading system is tricky.

99% of time I've got a center position tile (when for ex. I exit my house in village) named tile_0_0.png with its ID, next to this tile is 0_1, 0_-1, 1_1 etc.. When I do teleport (using milestone) then place when I teleported is my center, so H&H creates new folder (with new date XXXX-XX-XX XX.XX.XX) and place it there new tile_0_0. It's fine.

Problem is when I've got ex. I've got my village with tile_0_0 (and 3 tiles around, so it varies from 0_-1 to 0_1), and then I enter mine hole which is located inside my village. Suddenly, in the same folder, I've got tile_-21_20.png which is single tile from -1 mine level and the rest of the tiles from -1 are in different folder (but again, all tiles starts from tile_0_0 in -1)

I don't know why single random tiles, with distance coords like -21_20 are placed in the same folder. It destroys my concept where single folder is like slice of single layer from level (0, caves -1, mine -2) etc which are merged into existing layers (ex. I merge existing terrains around my village into layer on which is my village; when I mine on -2 and discover new caves I merge them into layer with previous -2 tiles)

Is it a bug or map system works differently?