Location uncetainty is intended to describe positional uncertainty associated with a geometry, not to alter or replace the geometry itself. Uncertainty values are expressed in the units of the geometry’s CRS and may be provided using axis-based or radial (horizontal/vertical) representations. Multiple representations may coexist and are considered alternative expressions of the same uncertainty.
Database handle for the object. It is of XML type ID, so is constrained to beunique in the XML document within which it occurs. An external identifier for the object inthe form of a URI may be constructed using standard XML and XPointer methods. This is doneby concatenating the URI for the document, a fragment separator, and the value of the idattribute.