Map Data: False Assumptions
One of my favorites on this topic is US ZIP codes. Most people tend to think that ZIP codes are contiguous geographic subdivisions. Most people also tend to think of a ZIP code as a contained part of some administrative boundary.<p>To grossly oversimplify, ZIP codes are essentially mail delivery routes. They are paths, not borders.<p>My ZIP code is serviced by the post office of a neighboring town. Almost every single online service I interact with that needs my address refuses to accept my actual town in my address, but instead replaces it, based on the ZIP code, with the neighboring town. The same is true for most GPS navigation.