ST_M — Returns the M coordinate of a Point.
float ST_M(geometry a_point
Return the M crdinate of a Point, or NULL if not available. Input must be a Point.
This is not (yet) part of the OGC spec, but is listed here to complete the point coordinate extractor function list.
This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.
This method implements the SQL/MM specification.
This function supports 3d and will not drop the z-index.