A GIS viewer allows users without Geographical Information Systems (GIS) software on their computer to view and print maps created in GIS formats. Some types of these viewers can also contain tools for map editing and spatial analysis. There are also web-based viewers, which generally contain large amounts of downloadable geographic data. A GIS viewer is useful for people who often need to view, print, and share maps, but are not generally responsible for editing them.
Several types of GIS viewer are available for download or purchase, and some are even offered for free. Each has a different set of capabilities, so someone needing a viewer should examine the options and determine which one best suits his or her needs. Some viewers are very basic, and contain only tools similar to those found in image viewers, while others are actually capable of editing maps and performing some other functions of GIS software.
The average GIS viewer can open the file types commonly used in GIS software, including shapefiles, raster and vector data, DBF database files, and image files. These viewers also have most of the features usually found in image viewing applications, like zooming, panning, and printing. They can also be used for viewing and querying database tables related to the map layers. It is possible to view both the map layout and the page layout for the files.
More complex viewers generally include various tools for editing maps and performing spatial analysis. Common editing tools include changing vector data, converting between coordinate systems, and adding photos and other information. Database tables can also be added and joined to the map features. Most viewing software cannot create data, but some has limited functionality in this area. GIS viewers are usually capable of performing some types of spatial analysis, such as a proximity search.
In addition to desktop GIS viewers, there are also many web-based ones provided by various organizations. For example, some United States government agencies, such as the U.S. Geological Survey (USGS), provide online access to large amounts of geographical data. Most web viewers provide basic map data, like boundaries, roads, and water bodies. Soil type, land use, population density, and many other data sets may also be found on various web viewers, along with database files pertinent to the map files. Most online versions also allow the data to be downloaded and used with GIS software.