Glossary for Geospatial Science

virtual field: A TNTmips database field that draws information from other database fields.  This information can be used directly or combined with the information from other fields or additional components.  There are two types of virtual fields: numeric, which are referred to as computed fields, or strings, which are called string expression fields.  An example of a computed field is population density, which may take population from one table, area from another, make the division and apply appropriate conversion factors for the desired output units.  A string expression field might concatenate the contents of separate fields, such as section, township, and range or create a multiline DataTip from a number of different fields, such as address, owner name, and property value for a parcels vector object.