geography Data Type Method Reference
Applies To: SQL Server 2014, SQL Server 2016 Preview
Topic Status: Some information in this topic is preview and subject to change in future releases. Preview information describes new features or changes to existing features in Microsoft SQL Server 2016 Community Technology Preview 2 (CTP2).
SQL Server supports a set of methods for the geography spatial data type, including methods on geography that are defined by the Open Geospatial Consortium (OGC) standard and a set of Microsoft extensions to that standard.
The error tolerance for the geography methods can be as large as 1.0e-7 * extents. The extents refer to the approximate maximal distance between points of the geography object.