Locating map features correctly in relation to their actual locations on the surface of the earth. Features on digital maps used in a GIS should represent, as faithfully as possible, the true geographic locations of places on the earth and the true spatial relationships between these places on the earth. One important way to aid this endeavor is to register key points in the digital map to the real world coordinates of those points on the ground. These real world coordinates should be in one or another of the recognized projections, units, and datums. The map is then said to be "in control." Doing this will greatly aid the internal consistency and accuracy of the digital map and support the use of this digital map with any others that are similarly in control. This is not the same as having your base map tied to the Public Land Survey system (PLSS) of townships and sections. The PLSS is important in land ownership descriptions, but its section corners may or may not have geodetic control coordinates (coordinates representing a position on the earth in an established coordinate system) established for them.

A network of carefully measured horizontal and vertical points. An accurate geodetic network provides the foundation for photogrammetric mapping.