Units describing the way geographies are stored in a data source.
public enum GeographyUnit
The geography unit defines how your map data is stored. More specifically, it describes what the change in X and Y mean in relationship to the data itself. For example, if your data is stored in a geographic unit of feet, an increase of one on the x-axis means that you've moved one foot in the X direction. Nearly all map data is stored using three simple units, which are decimal degrees, feet, and meters. It is important to note that this has very little to do with the projection that the data is in.