GIS (geographic information system) has various layers representing different sets of data. Some general examples are the following: hydrology - water patterns, topography - surface land features, ecology - interactions between vegetation and animal life, geology - subsurface land features, land use, utilities, soil types, streets, land parcels, other human characteristics such as demographic or socioeconomic. Layers can be sorted into two groups, physical layers and human layers. Physical layers are information about the natural features of an area. Human layers are facts about people, their structures, or their interactions with the land.