Microsoft® SQL Server 2012 Unleashed

Working with Geography Data

The GEOGRAPHY data type is also implemented as a .NET CLR data type in SQL Server. Unlike the GEOMETRY data type in which locations are defined in terms of X and Y coordinates that can conceivably extend to infinity, the GEOGRAPHY type represents data in a round-Earth coordinate system. Whereas flat models do not “wrap around,” the round-Earth coordinate system does wrap around such that if you start at a point on the globe and continue in one direction, you eventually return to the starting point.

Because defining points on a ball using X and Y is not very practical, the GEOGRAPHY data type instead defines points using angles. The SQL Server GEOGRAPHY data type stores ellipsoidal (round-Earth) data as GPS latitude ...