Section 2.4.9 Annotation


Spatial information often includes text and symbols. Text may be used as a label. It may also refer to a general region with an ill defined boundary, such as Pacific Ocean or Blue Ridge Mountains. Symbols may be used to indicate swamps, airports, historic sites, etc. The definition of text or symbols includes at least one point to indicate where the text is to be placed. In the case of text on a curve or multiple lines of text, a series of points are given. Text and symbols are modelled on the Computer Graphics Metafile specification.

Text and symbols must also be spatially referenced. An object from the class Annotation includes an object from the class TextOrSymbol, as well as an object from the class SpatialReferencing. The structure of Annotation is analogous to that of SpatialObject, which has one object from the class GeometricObject and another from SpatialReferencing. Note that Annotation is not related through the type hierarchy to either GeographicObject or SpatialObject. As with geographic objects, annotation may be included in a spatial data set.


Links to the SAIF 3.1 Specification document and the complete SAIF class list