Historical geographic information system

A historical geographic information system (also written as historical GIS or HGIS) is a geographic information system that may display, store and analyze data of past geographies and track changes in time. It can be regarded as a tool for historical geography.

Techniques used in HGIS

 * Digitization and georeferencing of historical maps: Old maps may contain valuable information about the past. By adding coordinates to such maps, they may be added as a feature layer to modern GIS data: This facilitates comparison of different map layers showing the geography at different times. The maps may be further enhanced by techniques such as rubbersheeting, which spatially warps the data to fit with more accurate modern maps.
 * Reconstruction of past boundaries: By creating polygons of former political entities, administrative sub-divisions and other types of borders, their evolution as well as aggregated statistics can be compared through time.
 * Georeferencing of historical microdata (such as census or parish records): This enables the use of spatial analysis to historical data.

Notable historical GIS projects

 * China Historical GIS is a project on Imperial China developed by Harvard University and Fudan University.
 * David Rumsey Historical Map Collection is one of the world's largest map collections, which has digitized and georeferenced a large part of its collection and published it on the internet.
 * Electronic Cultural Atlas Initiative (ECAI) is a clearinghouse for the exchange of metadata of Historical GIS. Maintained by the University of California, Berkeley.
 * Euratlas History Maps is a historical atlas of Europe from year 1 to present days with one map per century. The maps depict sovereign states as well as administrative divisions and dependent territories.
 * Great Britain Historical GIS is a GIS-enabled database holding diverse geo-referenced maps, statistics, gazetteers and travel writing, especially for the period 1801–2001 covered by British censuses. Created and maintained by Portsmouth University.
 * HistoAtlas is an open historical geographical information system that tries to build a free historical atlas of the world.
 * National Historical Geographic Information System (NHGIS) is a system for displaying and analyzing Census tracts and tract changes in the United States.

Software or web services developed for Historical GIS

 * Google Earth added a time line feature in version 4 (2006) that enables simple temporal browsing of spatial data.
 * TimeMap is a Java open-source applet (or program) for browsing spatial-temporal data and ECAI data sets. Developed by the department of archaeology University of Sydney.