Historical GIS: Mapping the Past to Understand the Future

Article excerpt

Call it what you like-the resurgence of geography, the reinvention of maps, or the vindication of cartographybut the increasing prominence of geographic information systems (GISs) becomes more pronounced every day. Twenty years ago, most GIS products were designed for businesses to track sales and identify potential new markets. Today they're infiltrating many other disciplines and becoming part of everyday life.

Before launching a review of GIS implementations, I should define the technology. According to ESRI's Guide to Geographic Information Systems, "GIS is a collection of computer hardware, software, and geographic data for capturing, managing, analyzing, and displaying all forms of geographically referenced information" (www.gis.com/whatisgis/index.html). With its capabilities for spatial analysis, GIS can reveal patterns and relationships among data that are not readily apparent in spreadsheets or other statistical packages. It's used for land use planning, utilities management, infrastructural planning, market analysis, and real estate analysis. Probably the very first use of a geographic information system, long before computers were invented or GIS was a recognized acronym, was John Snow's map of the 1854 cholera outbreak in London. By plotting cholera deaths on a map of London, he deduced that contaminated water from a Broad Street pump was the cause.

Essentially, GIS contains two types of information: attribute date (statistical) and spatial data (location), applied within a mapping context. To create a historical GIS, a third type of data is necessary-temporal.

GEOGRAPHY MEETS HISTORY

Historical GIS (HGIS) is an emerging field that uses GIS to research the geographies of the past. Regarded as a sub field of historical geography, HGIS displays, stores, and analyzes data of past geographies and tracks changes over time. Researchers can then perform spatial analysis on historical data. By combining maps and temporal data, you can visualize urban growth, environmental change, weather patterns, and other social and scientific changes.

HGIS gives historical researchers the ability to map change over time by scanning, geo referencing, reprojecting, scaling, and layering historical maps from different eras and comparing these maps to maps showing current locations of both natural and cultural features. Examples include population movement, distribution of wealth, and location of infrastructure.

However, HGIS goes beyond georeferencing and using historical maps. Historical data also comes into play. It can help expand the spatial analysis of historical materials by collating and mapping historical data derived from many different kinds of historical resources such as letters, diaries, sketches, census data, and voting records.

NOTABLE NATIONAL HGIS PROJECTS

GIS is currently used by historians to discover and integrate historical research resources and to display those research results in some form of visualization. This has resulted in digital archives of interest to researchers. Examples of these archives are contained in national HGIS projects, intended primarily for social science research.

The University of Portsmouth (U.K.) created and maintains the Great Britain Historical Geographical Information System (www.gbhgis.org). This digital collection shows the changes over time within British regions-its information sources include census reports (1801-2001), historical gazetteers, travelers' stories, and historic maps. The database holds maps, statistics (social, economic, electoral), and text.

Public access to this collection is on the "Vision of Britain" site (www.visionofbritain.org.uk). It is designed as a public resource into local history, trends in land use, geography of infant mortality in the inter-war period, and so on. You can search by place (postcode or place name) or by clicking on a region on the map. You can then zoom in, zoom out, pan, and ask for more information. …