There were several methods in
data_unit_tiles.py that were generic spatial operations, i.e. spatial operations that can apply to situations/cases other than those involving data-unit tiles. As I am about to add (see note) more methods that carry out spatial operations, I have split
data_unit_tiles.py in two:
spatial.py, which contains methods that carry out spatial operations on polygons
data_unit_tiles.py, which contains tools associated with the data-unit tiles (as before)
Note: In a separate branch.