direction.xsd See ISO/DIS 19136 Clause 18. The direction schema components provide the GML Application Schema developer with a standard property element to describe direction, and associated objects that may be used to express orientation, direction, heading, bearing or other directional aspects of geographic features. The property gml:direction is intended as a pre-defined property expressing a direction to be assigned to features defined in a GML application schema. Direction vectors are specified by providing components of a vector. deprecated direction descriptions are specified by a compass point code, a keyword, a textual description or a reference to a description. A gml:compassPoint is specified by a simple enumeration. In addition, thre elements to contain text-based descriptions of direction are provided. If the direction is specified using a term from a list, gml:keyword should be used, and the list indicated using the value of the codeSpace attribute. if the direction is decribed in prose, gml:direction or gml:reference should be used, allowing the value to be included inline or by reference. These directions are necessarily approximate, giving direction with a precision of 22.5°. It is thus generally unnecessary to specify the reference frame, though this may be detailed in the definition of a GML application language.