Posted on February 4th, 2014

G-FAQ – What is GIS?

In this three-part edition of the Geospatial Frequently Asked Question (G-FAQ), I try to a question that I am sure most of you have been asked at least once. Now I say try to answer the broad question, “What is GIS?” as no matter how simple, or how complex I make this discussion, I will never be able to please everyone with what I come up with. That said, I take the approach here of moving from the most simple to the most complex view of GIS, with some history and real world use cases included. So sit back and enjoy as I jump head first into this burly topic!

This G-FAQ series will be centered around three core questions:

What is GIS: is it just computer software or is it a science? How did GIS develop into an established field of study? How does GIS work and what can you use it for?

While it might seem odd for me to use the acronym ‘GIS’ without first defining it, you will now see why I made the conscious choice to do so, as in many ways it gets to the heart of much of the discussion to follow. The term GIS was coined in the early 1960’s, and most credit English geographer, Roger F. Tomlinson, as using it first in 1962 to stand for Geographic Information Systems. Today, many mapping professionals would still tell you that GIS stands for G.I. Systems; but if you were to ask an academic, many would tell you it stands for G.I. Sciences – and here we are at the heart of the debate already, is GIS a software package or is it a science??

The Many Definitions of GIS

Now that you know what GIS stands for, well kind of at least, let’s see if we can make sense of the many definitions of the technology you will find. After surveying a variety of academic and professional resources, I feel that the definitions of GIS can be lumped into four broad categories which build upon and expand from each other.

  1. GIS as a Toolbox

    The most simple way to define GIS is as a digital mapping software. It is the ‘natural,’ digital evolution of the 18th century cartographer’s pen, paper and compass. In this view, GIS is a software package that can store, retrieve, analyze and display data with latitude and longitude values (i.e. spatial data such as roads, school locations or topography). A GIS contains a set of standardized tools which manipulate, analyze, format, etc. your various layers of spatial data. A key component of GIS software is the ability to tie attributes (such as the number of lanes a road has) to a spatial location in a database – we will discuss this point in more detail as it is an important one. Even in this, the most simplistic view of GIS, it is not just a software but it is a system of at least four components: spatial data; software to link the data, computer hardware and network; professionals to use the software; and the analysis, visualization and maintenance of the spatial database.

  2. GIS as a decision support system

    As we move up the levels of GIS definitions, what you will see is that each one acknowledges the basic tenements of the previous definition, and then adds on a layer of complexity. In this view of GIS, it is a digital mapping software as described above with the added notion of the ability to support decision making. These decision can be political, cultural, economic or environmental (to name a few) in nature; and GIS is the tool that lets you make a decision in as unbiased a fashion as possible. GIS then is a toolkit that helps individuals, companies, politicians, etc. make more informed decisions by employing the most accurate and pertinent spatial information available.

    As a quick side note, it is now possible to distinguish GIS from another mapping program of sorts used commonly in the world of engineering, CAD. While CAD creates maps as can GIS, it does not give users a set of spatial operations to manipulate, analyze, sort, etc. data so that informed decisions can be made.

  3. GIS as a part of society

    In this definition of GIS, it is seen as a mapping software that supports decision-making but it sees these decisions, and more broadly the role of GIS, as a part of society. GIS becomes a part of society when it is used to make decisions that shape the way we all work, live and play. There are few, if any, decisions that space, and then adjunctly GIS, is not at least a part of. From transportation planning, to the site for a new park, to the advertisements we see, this ‘software package’ is integral to the society we live in.

    This definition does not stop here as it also acknowledges the two-way nature of decision making. What I mean here is that no decision is made in a vacuum, societal trends and values impact each and every choice we make. And as a human ultimately completes a GIS analysis (or pushes the buttons, so to speak), it is impossible to separate the impacts society has on these decisions.

    So too sum this up: (1) GIS shapes decisions, (2) these decisions shape society and (3) in turn society shapes the decisions we make in GIS!

  4. GIS as a science

    This is the most holistic view of GIS, admitting its role in society for decision-making and map-making, but it takes it a step farther claiming it to be part of its own scientific discipline. According to this definition, GIS is an interdisciplinary field containing elements of cartography, computer science, statistics and geography (just to name a few!). The idea here is that GIS evolves into a science when the field looks at the methodology used to create its analyses and then the biases behind the decisions reached with the software. GIScience then becomes a more standardized way to analyze the world around us and its social processes to make informed and repeatable decisions. Simply stated, GIS is a way to understand and interpret the world around us from a spatial perspective.

    GISLounge_wordcloudA word cloud created from the RSS feed on In this word cloud, you can see many of the defining features of GIS mentioned in this article. (Created with Wordle)

    As more evidence of GIS as a science and not just software, consider that many of the principles upon which it is built do not exist on a computer only, for example scale and positional accuracy. These principles were just as important and valid when cartography was ‘analog,’ and no one questions cartography as a valid field of scientific study.

    As you can see, the four definitions for GIS presented here are not mutually exclusive, rather they build upon one another, extending the complexity of the definition in each case. At the root of this question is the very basic debate as to whether GIS is a software or a science; and similarly, if with GIS you are mapping or completing an analysis. While I have not answered the question of what is GIS in full here, what I have laid is the foundation required to answer it which I will attempt in the final edition of this G-FAQ series. Next month, we take a look at the historical development of GIS.

Do you have an idea for a future G-FAQ? If so, let me know by email at

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Brock Adam McCarty
Map Wizard
(720) 470-7988

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