Metadata, Geospatial

A metadata record is a file of information that describes the basic characteristics of a data resource. It represents the “who,” “what,” “when,” “where,” “why,” and “how” of the data. Geospatial metadata are used to document digital geographic data formatted as geographic information system (GIS) files, geospatial databases, and earth imagery. The information in the metadata record can be used to apply, manage, archive, and distribute the geospatial data.

Metadata make up the component of the data resource that provides context. All data resources represent an abstraction of some form. This is particularly true of geospatial data, in which real-world forests or transportation networks are reduced to a set of points, lines, and polygons. Metadata provide the data consumer with critical information about the data developer's purpose in abstracting the data, the decisions made during the abstraction, and the data elements derived from the abstraction. Metadata preserve the ontological pedigree of the data resource.

The key components of a geospatial metadata record are as follows:

• Identification information: Information that uniquely identifies the data, including citation, abstract, geographic, and temporal extents
• Constraint information: Restrictions placed on the data
• Data quality information: Data processing history (lineage) and assessments as to the completeness, logical consistency, positional accuracy, thematic accuracy, and temporal accuracy of the data
• Maintenance information: Scope and frequency of data updates
• Spatial representation information: Grid or vector mechanisms used to represent the data
• Reference system information: Geographic and temporal reference systems used to present the data
• Content information: Attributes used to describe the data features
• Portrayal catalog information: Symbol sets used to represent the data features
• Distribution information: Options and contacts for obtaining the data resource