• Article

STBuffer (geography Data Type)

Returns a geography object that represents the union of all points whose distance from a geography instance is less than or equal to a specified value.

Syntax

.STBuffer ( distance )

Arguments

  • distance
    Is a value of type float (double in the .NET Framework) specifying the distance from the geography instance around which to calculate the buffer.

Return Types

SQL Server return type: geography

CLR return type: SqlGeography

Remarks

STBuffer() calculates a buffer in the same manner as BufferWithTolerance, specifying tolerance = distance * .001 and relative = false.

A negative buffer removes all points within the given distance of the boundary of the geography instance.

The error between the theorectical and computed buffer is max(tolerance, extents * 1.E-7) where tolerance = distance * .001. For more information on extents, see geography Data Type Method Reference.

Examples

The following example creates a LineStringgeography instance. It then uses STBuffer() to return the region within 1 meter of the instance.

DECLARE @g geography;
SET @g = geography::STGeomFromText('LINESTRING(-122.360 47.656, -122.343 47.656)', 4326);
SELECT @g.STBuffer(1).ToString();