Detailed, minute ground drawing

There is a detailed map of each town and city in Japan. Each map is a tome that runs around ¥20,000.  The shape and orientation of every building and house is shown, and there is even a family or business name attached. So how to they collect all the necessary information?

Why, door-to-door of course.

A man called at our door, carrying a large clipboard with the section of the map showing our neighborhood. The map was scribbled over with dozens of modifications, and he asked what name should go with our house. The nameplate on our house says 金山, the name of the owner. The man explained that, since the map would be used mostly by delivery services, he wanted the current occupants’ names.