Getting Started with the geography Data Type

The geography spatial data type, geography, is implemented as a .NET common language runtime (CLR) data type in SQL Server. This type represents data in a round-earth coordinate system. The SQL Server geography data type stores ellipsoidal (round-earth) data, such as GPS latitude and longitude coordinates.

Registering the geography Type

The geography type is predefined and available in each database. You can create table columns of type geography and operate on geography data in the same manner as you would use other system-supplied types.


The following examples show how to add and query geography data. The first example creates a table with an identity column and a geography column GeogCol1. A third column renders the geography column into its Open Geospatial Consortium (OGC) Well-Known Text (WKT) representation, and uses the STAsText() method. Two rows are then inserted: one row contains a LineString instance of geography, and one row contains a Polygon instance.

IF OBJECT_ID ( 'dbo.SpatialTable', 'U' ) IS NOT NULL 
    DROP TABLE dbo.SpatialTable;

CREATE TABLE SpatialTable 
    ( id int IDENTITY (1,1),
    GeogCol1 geography, 
    GeogCol2 AS GeogCol1.STAsText() );

INSERT INTO SpatialTable (GeogCol1)
VALUES (geography::STGeomFromText('LINESTRING(-122.360 47.656, -122.343 47.656)', 4326));

INSERT INTO SpatialTable (GeogCol1)
VALUES (geography::STGeomFromText('POLYGON((-122.358 47.653, -122.348 47.649, -122.348 47.658, -122.358 47.658, -122.358 47.653))', 4326));

The second example uses the STIntersection() method to return the points where the two previously inserted geography instances intersect.

DECLARE @geog1 geography;
DECLARE @geog2 geography;
DECLARE @result geography;

SELECT @geog1 = GeogCol1 FROM SpatialTable WHERE id = 1;
SELECT @geog2 = GeogCol1 FROM SpatialTable WHERE id = 2;
SELECT @result = @geog1.STIntersection(@geog2);
SELECT @result.STAsText();