Editing Geographic information system (section)

===Cartographic modeling===
{{main | Map algebra}}
[[File:gislayers.jpg|300px|right|thumb| An example of use of layers in a GIS application. In this example, the forest-cover layer (light green) forms the bottom layer, with the [[topography|topographic]] layer (contour lines) over it. Next up is a standing water layer (pond, lake) and then a flowing water layer (stream, river), followed by the boundary layer and finally the road layer on top. The order is very important in order to properly display the final result. Note that the ponds are layered under the streams, so that a stream line can be seen overlying one of the ponds.]]

[[Dana Tomlin]] coined the term ''cartographic modeling'' in his PhD dissertation (1983); he later used it in the title of his book, ''Geographic Information Systems and Cartographic Modeling'' (1990).<ref>{{cite book | last1 = Tomlin | first1 = C. Dana | author-link1 = Dana Tomlin | title = Geographic information systems and cartographic modeling | url = https://archive.org/details/geographicinform00toml | url-access = registration | series = Prentice Hall series in geographic information science | publisher = Prentice Hall | date = 1990 | isbn = 9780133509274 | access-date = 5 January 2017}}</ref> [[cartographic design|Cartographic modeling]] refers to a process where several thematic [[layer (disambiguation)|layers]] of the same area are produced, processed, and analyzed. Tomlin used raster layers, but the overlay method (see below) can be used more generally. Operations on map layers can be combined into algorithms, and eventually into simulation or optimization models.