scmJS docs

TILE

The terrain with the doodads left out: what is under each doodad. Only editors read it, to put the ground back when a doodad is removed.

Name TILE (54 49 4C 45)
Size 2 bytes per tile: width × height × 2.
Read by Editors only. The game skips it.
Required No.
More than one copy Every copy is written over the start of the same fixed-size space, in file order, so a later copy replaces only as many bytes as it carries.
In scmJS Read, and written again when you change what it holds.