Spatial metadata and GIS for decision support

The proliferation of GIS technology has greatly increased the access to and the usage of spatial data. Making maps is relatively easy even for those who do not have much cartographic training. Nonetheless, the concerns for spatial data quality among GIS and spatial data users have just began to sprout partly because information about spatial data quality is not readily available or useful. Metadata, which refer to data describing data, include the quality and accuracy information of the data. The Federal Geographic Data Committee has proposed content standards of metadata for spatial databases. However, the standards are not adequate to document the spatial variation in data quality in geographic data. The paper argues that information about the quality of spatial data over a geographical area, which can be regarded as spatial metadata, should be derived and reported to help users of spatial data to make intelligent spatial decisions or policy formulations. While cartographers focus on the representation of spatial data quality, and statisticians emphasize the quantitative measures of data quality, this paper proposes that GIS are logical tools to assess certain types of error in spatial databases because GIS are widely used to gather, manipulate, analyze, and display spatial data. A framework is proposed to derive several types of data quality information using GIS. These types of quality information include positional accuracy, completeness, attribute accuracy, and to some extent logical consistency. However, not every type of spatial metadata can be derived from GIS.