M (geometry Data Type)
The M (measure) value of the geometry instance. The semantics of the measure value are user-defined.
The following example creates a Point instance with Z (elevation) and M (measure) values and uses M to fetch the M value of the instance.
DECLARE @g geometry; SET @g = geometry::STGeomFromText('POINT(1 2 3 4)', 0); SELECT @g.M;