What is GIS?

There are as many definitions of geographic information systems (GIS) as there are GIS users. ESRI defines GIS as:

An organized collection of computer hardware, software, geographic data, and personnel designed to efficiently capture, store, update, manipulate, analyze, and display all forms of geographically referenced information. Certain complex spatial operations are possible with a GIS that would be very difficult, time-consuming, or impractival otherwise. (ESRI, 1991)

This is a common definition of GIS and for most people means very little. To better understand GIS, you need to understand its history and what makes GIS a unique technology.

Maps have been utilized for at least 25,000 years. Prehistoric maps focused primarily on mapping the “known world” or as navigation aids, whether for shipping or simple maps to good hunting grounds.

Over the last several centuries, maps increasingly became important for depicting jurisdictional boundaries, land uses, social and demographic information, distribution of populations and natural resources, and many other features relevant to land management and wealth. Whether it is a topic as simple as a general reference map to soil types, maps are  purely a form of communication. With the advent of maps, a small profession called cartography emerged.

Cartographers for centuries went through the tedious process of research, compilation, and production of maps. Not just preparing reference and navigation maps, but also poly-thematic maps to present spatial information in news ways. Much of this early analysis was done to assist decision-makers, as it is used today. A common method of this “overlay analysis” was to prepare a series of individual thematic maps on mylar and stack the various themes together to visualize the relationships. One of the best references for this type of analysis was documented and published in “Three Approaches to Environmental Resource Analysis” (1967). Much of modern GIS can trace its lineage directly to this research paper. This should be required reading for anyone using GIS.

Technological advances allowed the marriage of the art and science of cartography with computers to help use better understand the spatial relationships that surround us. Computers facilitate the analysis of data in more complex ways that can be done manually. Two issues have emerged with GIS. The first is that GIS is a holistic field. GIS can be used in virtually any field and many fields adopted this new technology to help them manage their spatial information. The other problem was that during this process, many cartographers stuck their heads in the sand rather than nurturing this new technology.

So what make GIS unique? Geographic information systems are both a tool and a methodology for the management, analysis, and display of spatial information. There are three primary components to GIS. The combination of these components differentiates GIS from computer-aided design (CAD) and illustration programs, like Adobe Illustrator.

The analysis and data components make GIS unique compared to CAD and illustration programs, especially the analysis component.

Three Components of GIS

Three Components of GIS

Data Component
The data component is where GIS starts. Unlike CAD and illustration programs, GIS data typically has additional tabular data associated with the vector or raster representation. For example, a vector polygon illustrating the boundary of a county may have a table associated with it containing the area, overall population, population by age groups, population by ethnic distribution, etc. In CAD or illustration programs, this additional tabular information would not be included. In addition, raster data could be aerial photography, elevation data, multi-spectral imagery, etc.

Data can be used in the analysis component and the display component. Also, data can be created from the analysis component and reused in the analysis component. This ability to create data from data is one of the unique abilities of GIS.

Analysis Component
The analysis component is what makes GIS truly unique from other programs. The ability to take existing data, interpret, process, and create new datasets or display the information is the power of GIS. There are no limits to what can be done. Through unique implementations of existing tools, creation of new tools and scripts, and the application of user experience, GIS can analyze complex data far more efficiently than a manual process.

Display Component
All applications have this component in one form or another. Whether this is a print map or a web map, this is how we communicate with the GIS user and the map user.

The thing to remember about GIS is that is crosses all fields. It is another holistic information technology. There are always topics “GIS for this…” and “GIS for that…”. GIS, like cartography, does not care what it is being used for. Anything that has a spatial location can by analyzed and displayed by a GIS system. As a cartographer, I see GIS as the technological enabler for my profession.

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