G.I.S.
Sean Breazeal
GIS, which stands for Geographic
Information System, is a modern, cutting edge technology aiding cartographers and planners
in all fields. It is a special set of software that incorporates the powerful mapping
abilities of today's personal computers with extensive databases to create a world of
possibilities in planning, forecasting, site-location, and myriad other functions with
maps and spatial relationships involved. Before going on further, there are a few terms
I'll need to throw around that the reader should be familiar with. None of this is
complex, just new! Before I jump in, let me state that I am not the best explainer of
things, so bear with me!
GIS got started in the late 60's and early 70's as computers began to grow more powerful.
Before then, the sheer mass of data was more than even a large computer could handle. Jack
Dangermond, the president of ESRI (Environmental Systems Research Institute), and some of
his contemporaries developed the first true GIS for the census department. The technology
spread like wildfire in the 80's, with GIS systems being ported to Unix, Solaris, IRIX,
and other development platforms. ARC/Info was and still is the flagship GIS, growing more
powerful and adding zillions of geographic data processing functions. In 1991 ESRI really
made GIS accessible with the release of ArcView for the Windows PC. It was the first GIS
with a modern graphical interface, but it's functionality was limited to viewing data. The
current ArcView 3.2 and future releases feature a powerful programming language and basic
editing and data creation functions.
How does it work? Well, a GIS stores its data in layers. Each layer represents
a different distinct geographic feature. A single layer could represent a road system,
another could represent a city's building locations. You can think of the layers as
transparent sheets that can be overlaid on top of each other in as many combinations as
is needed. What makes a GIS work is twofold.
First, every feature in your layer, each street, stream, building, whatever, has a
corresponding set of data in a table. A table is essentially a spreadsheet that links
values in the table to a geographic feature. This data can be accessed by pointing and
clicking on the map. Clicking on a stream for example might bring up a window describing
the steam's length, depth, rate of flow, and pollution level. A building might have data
on the architect, year constructed, cost, height, number of parking spaces, anything that
the GIS designers may wish to store. Secondly, and most powerfully, a GIS can analyze data
from multiple layers at once to find relationships. This is the heart of any GIS system. A
little later, I'll describe some uses for modern GIS systems.
A GIS can tell what direction features lie and where things are in relation to each other
by a complex system of topology. Topology is the scientific study of location, and the GIS
has built-in topological algorithms to help it. It records the origin of a line, and it's
final point, so it then knows the "direction" that the line travels. At the
intersections of two lines, a "node" is placed and the node stores information
about what lines enter and exit it and the directions they are coming from.
Virtually all GIS data came from existing paper maps. If you're lucky, then the lines,
points, and polygons that represent your features of interest are already in existence
somewhere. More often than not, however, you'll have to create this data yourself. Doing
so isn't hard, just very mind-numbing and time-consuming. There are modern processes that
take the tedium out of having to hand digitize every single point and line in by hand, but
error checking and processing after those processes take time as well. Creating data is
nothing more than selecting the right area of the world in the GIS and click, click, click
to add the points and lines. When a point or line is added, you can enter data about it on
the fly if desired, or you can add it later when digitizing is complete. Either way, it is
the data behind the linework that makes a GIS what it is. Entering data into the GIS about
the features can be as simple as typing in a spreadsheet in more modern systems, to as
clunky and archaic as a totally command line based system (a la DOS) for older versions.
The GIS assigns each feature a unique identifier number so that it can keep everything
straight.
GIS is now used in countless applications in ways that it may not at first be apparent.
Instead of listing a ton, let me go in-depth into the classic GIS application that put the
technology on the map (oh, the puns!): site location of a business. Let's suppose that you
are manager of a large chain of fast-food restaurants. You are looking to enter a new city
and build a new franchise. Before you begin, you need to determine what variables are
important in locating a new restaurant. Beginning on the large scale, what would be the
best new city to enter? Fast food is very dependant on large customer volume, so you'd
likely want to pick a location that will have a moderately large population. If you had
data on the population of other towns in which you had restaurants you could easily
determine the average population per restaurant. This would help you narrow the choices.
Cities that lie on interstates have increased population flow. Think about how many
McDonalds you see at freeway exits. They're there for a reason!
Let's assume you found a city. Now you need to pick a spot in that city. You'll have to
decide if you want to be near other fast food joints or if you want to strike out alone at
a new spot (usually more desirable). Assuming you're going with a new spot the first
consideration is looking at the city's zoning maps and finding spots that allow commercial
construction of that size. Such maps are commonplace in GIS systems these days, just 10
years ago you'd be doing it all the digitizing by hand! Next you need to find a few
parcels of land that you can afford to build on. So in comes the land valuation study.
Again, it's fast food, so you need to find a high traffic location that fits all the above
criteria. If you're lucky, you whittle away the possible choices one by one until a site
matching all your criteria is found.
Other urban planning uses would be in predicting revenue income based on zoning changes,
and for predicting growth into new city annexes based on surrounding data. The link below
to ESRI's web site is a good showcase of the current uses of GIS in all facets of life.
What about a career in GIS? Anyone who loves maps and computers may be interested in a GIS
career. The educational requirements are not severe and the chances to be creative are
abundant! A prospective GIS candidate would want to take as many science and math classes
as possible in high school and enter a geographic degree program in college. There are
many subdisciplines in geography: cultural, urban, region-specific, remote sensing, GIS,
and others. In some ways, GIS blends all these together as it can be used in all of those
disciplines. Someone studying urban planning in a large city could definitely use a GIS to
make accessible the huge volume of data relating to land values, taxation, and utilities.
Sean Breazeal is a GIS expert working
for the State of Utah. He lives in Salt Lake City.