gml:GridFunction

gml:GridFunction provides an explicit mapping rule for grid geometries, i.e. the domain shall be a geometry of type grid.  It describes the mapping of grid posts (discrete point grid coverage) or grid cells (discrete surface coverage) to the values in the range set.
The gml:startPoint is the index position of a point in the grid that is mapped to the first point in the range set (this is also the index position of the first grid post).  If the gml:startPoint property is omitted the gml:startPoint is assumed to be equal to the value of gml:low in the gml:Grid geometry. Subsequent points in the mapping are determined by the value of the gml:sequenceRule.