Representation: Geographic Systems

Geographic information systems (GIS) apply geographic data models to describe how natural and constructed systems such as rivers, parcel cadastres, and transportation networks are located in space and interact with each other. Geographic data models are built by applying elements of a geographic information model to describe the spatial extents, attributes, interrelationships, and behaviors of the system under study. There are several generic geographic information models; cell‐based rasters are used for imagery and continuous phenomena, sets of features describe a collection of discrete geographic entities, graph elements are linked into networks, and finite‐element meshes in three‐dimensional space model topographical and other types of surfaces. Geographic data can also be structured to model temporal changes within geographic systems.