#datum

Datum-Free PNEZD: When the Numbers Look Like State Plane But Aren't Declared

A PNEZD CSV lands on your desk. The northings are in the 500,000s. The eastings are in the 1,800,000s. It looks like a clean state-plane file -- except nobody declared which state plane, which datum, or which units. Picking 'looks about right' from a dropdown can put your final coordinates 30 to 100 feet off the truth. Here's how to read the file before you import it, what assumptions you can and can't make from the magnitudes alone, and when to pick up the phone instead of guessing.