Completeness The final quality component involves a statement about the completeness of the data set. This includes consideration of holes in the data, unclassified areas, and any compilation procedures that may have caused data to be eliminated. The ease with which geographic data in a GIS can be used at any scale highlights the importance of detailed data quality information. Although a data set may not have a specific scale once it is loaded into the GIS database, it was produced with levels of accuracy and resolution that make it appropriate for use only at certain scales, and in combination with data of similar scales. Two sources of error, inherent and operational , contribute to the reduction in quality of the products that are generated by geographic information systems.
Inherent error is the error present in source documents and data.
While error will always exist in any scientific process, the aim within GIS processing should be to identify existing error in data sources and minimize the amount of error added during processing. Because of cost constraints it is often more appropriate to manage error than attempt to eliminate it. There is a trade-off between reducing the level of error in a data base and the cost to create and maintain the database. An awareness of the error status of different data sets will allow user to make a subjective statement on the quality and reliability of a product derived from GIS processing. The validity of any decisions based on a GIS product is directly related to the quality and reliability rating of the product.