Coordinate Systems and Datum

Geo-referencing is the technique of assigning location codes to points on Earth. There are many geo-referencing methods, including the use of landmarks and civic addresses. An effective system would provide a systematic way of yielding a unique code for each possible location. In other words, the location code of any position could be determined uniquely using a well-defined procedure. Moreover, given a code, the location it represents can also be derived. Both landmarks and civic addresses are not every effective geo-references because they are not unique.