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The Atlas covers the history of more than 3,000 counties and county equivalents in the United States from the early 1600s to 2000. [1] [2] It is available in print form or as downloadable files in shapefile, Keyhole Markup Language, and PDF formats, which are compatible with geographic information systems including Google Earth and ArcGIS.
U.S. Gazetteer, TIGER/Line shapefiles, census data. National Historical Geographic Information System NHGIS provides free of charge, aggregate census data and GIS-compatible boundary files for the United States between 1790 and 2012.
Shapefiles : are a data exchange format created by ESRI and one of the most widely used GIS/geodata formats. One "shapefile" usually include four different files : .shp, .shx, .dbf, .prj. First three files must all be present in order to use the data. Each shapefile can hold only one geometry type.
QGIS supports shapefiles, personal geodatabases, dxf, MapInfo, PostGIS, and other industry-standard formats. [5] Web services, including Web Map Service and Web Feature Service, are also supported to allow use of data from external sources. [6] QGIS integrates with other open-source GIS packages, including PostGIS, GRASS GIS, SAGA GIS, and ...
Basic GIS concept. A geographic information system (GIS) consists of integrated computer hardware and software that store, manage, analyze, edit, output, and visualize geographic data.
Shapefile – open, hybrid vector data format using SHP, SHX and DBF files (by ESRI) Spatial Data File – high-performance geodatabase format, native to MapGuide (by Autodesk ) TIGER – Topologically Integrated Geographic Encoding and Referencing
The GAUL always maintains global geographic layers (in shapefile format) with a unified coding system at the levels of country, first administrative (e.g. regions), and second administrative (e.g. districts). In addition, when data is available, it provides layers on a country-by-country basis down to third, fourth and lower levels.
This was most common from the 1970s through the early 1990s, because GIS software developers had to invent their own geometry data structures, but incorporated existing relational database file formats for the attributes. For example, the Esri Shapefile format includes the .dbf file from the DOS dBase software.