gml:PolarCS ia s two-dimensional coordinate system in which position is specified by the distance from the origin and the angle between the line from the origin to a point and a reference direction. A PolarCS shall have two gml:axis property elements.
The attribute gml:id supports provision of a handle for the XML element representing a GML Object. Its use is mandatory for all GML objects. It is of XML type ID, so is constrained to be unique in the XML document within which it occurs.
Source
<element name="PolarCS" type="gml:PolarCSType" substitutionGroup="gml:AbstractCoordinateSystem"><annotation><documentation>gml:PolarCS ia s two-dimensional coordinate system in which position is specified by the distance from the origin and the angle between the line from the origin to a point and a reference direction. A PolarCS shall have two gml:axis property elements.</documentation></annotation></element>