Procedures that determine the increase or decrease of a particular phenomenon based on changes in a number of other variables. The majority of spatial analytical functions currently support procedures that can be used to determine impact assessment on a modeled system. For instance, linear network data management systems that maintain utility facility networks (electric, water, etc.) provide procedures that depict the demand on an overall linear network based on specific changes made both in the physical structure of the network and in the demand schedule from customers. This type of system allows local government personnel to assess the impacts on a network, based on changes such as new development. Impact assessment systems are used for diverse functions such as (1) decision support for the approval or rejection of proposed land activities and (2) quantification of overall system impact of development for use in the determination of impact fees.