Define a GIS

A definition of a Geographical Information System (GIS) from the USGS (United States Geological Survey) states that

"A GIS is a computer system capable of capturing, storing, analyzing, and displaying geographically referenced information; that is, data identified according to location. Practitioners also define a GIS as including the procedures, operating personnel, and spatial data that go into the system."

Two components  make something a GIS: a map, and computer data, linked together. The map part, or the geographic coordinates, differentiates a GIS from a standard computer database.  In GIS, and especially in geospatial intelligence, we are looking for the spatial patterns.  Where do things happen (description), and then why do they happen there (analysis).

The military currently classifies this as geospatial intelligence or GEOINT (previous terms included "Mapping, Charting, and Geodesy" (MC&G) and "Geospatial Information and Services" (GI&S)):

"The term "geospatial intelligence" means the exploitation and analysis of imagery and geospatial information to describe, assess, and visually depict physical features and geographically referenced activities on the earth. Geospatial intelligence consists of imagery, imagery intelligence, and geospatial information."  (U.S. Code Title 10, 467)

The biggest problems for students using GIS deal with coordinates--when some of the map layers do not want to display on others, there are problems.  Without coordinates, a graphical map is just a "dumb picture", and the GIS software has no way to know where to plot the map.  The data must also stay in a GIS format to retain its full value; saving in a graphics format like JPEG loses all the associated data.

GIS programs store their data in tables, with rows and columns. Understanding GIS requires understanding computer databases. In the simplest cases the geographic coordinates for points can be included in the database table, but most cases require multiple files.

GIS is based on geography, and applies Tobler's first law of geography:

"Everything is related to everything else, but near things are more related than distant things."

Spatial patterns exist and prove to be important; GIS harness computers to look at maps and data and tease out the spatial relationships.

A GIS course will be a mixture of education and training:

Fundamentally GIS is about telling stories, and the stories involve spatial patterns of data.


Last revision 9/19/2017