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# M (geometry Data Type)

The M (measure) value of the geometry instance. The semantics of the measure value are user-defined.

SQL Server type: float

CLR type: SqlDouble

The value of this property is null if the geometry instance is not a Point, as well as for any Point instance for which it is not set.

This property is read-only.

M values are not used in any calculations made by the library and will not be carried through any library calculations.

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;