This was definitely non-trivial at the time. Even now the only way it would take "1-2 days tops" is if you use a naive design that ignores important edge cases

This was definitely non-trivial at the time. Even now the only way it would take "1-2 days tops" is if you use a naive design that ignores important edge cases and leverages a lot of code and computer science that did not exist then. Geospatial is hard.