Trust no one.
- Topological data is never read from disk. It is never imported. We don't trust TIGER or VMAP0 to be correctly integrated. In the case of VMAP0, I can tell you for a fact that it has errors. (I've never caught TIGER, but the older code wasn't very sensitive.
- Instead, all data is imported and sanitized on input by CGAL.
- Once CGAL has the data, we are home free; the 3.3.1 Planar map with an exact numeric type is rock solid.
The advantages of this are:
- It's as good as CGAL is (and CGAL is very, very good). Bad data can't ruin the party.
- Because bad data can't ruin the party, it's safe for third party use - that is, the tools can handle third party data that hasn't been "degunked".