What is GIS?


A GIS (Geographic Information System) is most commonly referred to as a mapping software that is used to present and analyze geospatial data -- data matched to a location. It is said that about 80% of the world's data can be geographically located. This makes GIS a powerful tool in manipulating, managing, and visualizing data. GIS is used in many disciplines and has become a critical tool in some fields for decision-making.

Examples of the tasks a GIS can help accomplish:

  • mapping crime locations
  • routing delivery drivers to a proper delivery location
  • locating the best site for a new business
  • mapping global shipping lanes
  • mapping economically challenged areas.


User views of GIS data

Often, the biggest hurdle in using a GIS is finding the right data and importing it into the software. Some GIS datasets are so large and complex that they require the use of a relational database for storage. GIS application developers often need database programming skills to perform complex GIS analyses efficiently.

GIS software works with specific data types to display data in 2-dimensional maps. There are two important data components:


  • The spatial component is the visual part of the data. Spatial data can be represented as raster data like aerial photographs or vector data made of points, lines, and polygons that depict the features on the earth. For example, area features like states and counties can be drawn as polygons, linear features like streams and streets can be drawn as lines, and locations of coffee shops can be represented with points. All of these features are drawn as individual layers and each layer can be chosen to be displayed or not. The layers can be jointly analyzed to help understand the possible impacts that one might have on the others.


  • The table data component is the tabular data that describes each feature appearing on a map. Each spatial feature in a GIS is associated with one row of table data. For example, a state's boundary will be associated with a row of the data table, containing state name, state FIPS code, total population, state capital, etc.


What can a GIS do?

GIS software has three primary uses.

  • Storage GIS packages have a unique way of storing data to link the table data attributes with the spatial component information. This is often callaed a geodatabase. Users interact with the graphical view of the data to access information about the viewed features. Geodatabases also store network topology rules that that define how features can be used in analyses, such as stream or traffic flows.

  • Visualization Most interaction with a GIS is performed through the mapping interface. Users can investigate data by panning or moving the map, zooming in or out, turning data layers on and off, creating thematic color schemes to symbolize data, and selecting features that are within a given distance of a clicked location on the map. One visualization tool that is growing in popularity is 3D-rendering. This ability to make a GIS map look more life-like provides much additional visual information.

  • Analysis The ability of a GIS to analyze data makes GIS more of a tool than just a map viewer. GIS packages contain rich tools that can process GIS data together to create new data sets. This processing, called geoprocessing, includes clipping a larger geographic area to a smaller second area, merging two dataset's tabular and spatial features, calculating summary statistics based on geographic areas, reclassifying image pixels, and determining and displaying information in user-defined buffer zones.



GIS at UD

GIS is used in over 40 departments and research centers at the University of Delaware. The use of GIS and image processing is growing steadily and is being incorporated into disciplines that have not traditionally used GIS technologies. UD maintains a campus-wide site license for ESRI GIS software. This software can be found in many public computing sites on campus. There is also an active community of GIS users that share data, ideas, and tips. For more information on GIS use at UD, visit the GIS@UD web site .