Editing Raster graphics (section)

===Geographic information systems===

Geographic phenomena are commonly represented in a raster format in [[Geographic information system|GIS]]. The raster grid is ''[[Georeferencing|georeferenced]]'', so that each pixel (commonly called a ''cell'' in GIS because the "picture" part of "pixel" is not relevant) represents a square region of geographic space.<ref name="Bolstad">{{cite book |last1=Bolstad |first1=Paul |title=GIS Fundamentals: A First Text on Geographic Information Systems |date=2008 |publisher=Eider Press |page=42 |edition=3rd}}</ref> The value of each cell then represents some measurable ([[Level of measurement|qualitative or quantitative]]) property of that region, typically conceptualized as a [[Field (geography)|field]]. Examples of fields commonly represented in rasters include: temperature, population density, soil moisture, land cover, surface elevation, etc. Two sampling models are used to derive cell values from the field: in a ''lattice'', the value is measured at the center point of each cell; in a ''grid'', the value is a summary (usually a mean or mode) of the value over the entire cell.