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Geographic Information Systems

Introduction to GIS


Following: Constructing and Sharing Maps

Geographic Information Systems (GIS) provide a powerful way to visualize and analyze spatially distributed data.

A Brief Overview of GIS

Numerous applications of GIS can be seen in our own Town of Amherst.

US CapitalsGeographic Information Systems (GIS) are a set of computer programs that can organize, display, and analyze spatially distributed data.

At its simplest, GIS is "mapping", providing a geographic arrangement of diverse information, allowing for visual comparison.

Such maps are therefore a powerful means to educate, in class and in publications.

Additional GIS tools can extract related features, provide geostatistical analysis, and generate 3D models and movies of time-dependent changes.

GIS has been applied in geology, biology, psychology, anthropology, sociology, linguistics, history, political science, economics, and many other fields.

GIS data is commonly in one of two forms:

Raster: A grid of rows and columns of colored cells.

These might represent photographic or scanned images.

Vector: A geometric shape, including points, lines, and polygons.

These might represent buildings, roads, and counties.

Either of these can have tables of data associated with them, e.g. elevation, population, financial values, etc.

These associated data can be used to color a map so that it conveys information with visual impact.

Some samples of GIS-produced maps for the town of Amherst are shown below, clear evidence of its cross-disciplinary value.

The data underlying these maps comes from many sources: the Town of Amherst, the State of Massachusetts, the U.S. Census Bureau, and the U.S. Geological Survey.

Overview Maps


Visible Orthographic Photograph

Scanned Map

Infrared Orthographic Photograph

Amherst's true colors are revealed by this orthophoto (a photo with perspective removed). It's a mosaic of many taken by airplane.
Cell Resolution = 0.152 m = 6 in.
A scanned USGS topographic map shows streets, buildings, open lands (green), and constant-elevation contours (brown lines).
Cell Resolution = 2.54 m = 8.33 ft = 100 in.
A Landsat 7 satellite image shows warmer areas (purple) and cooler areas (green), with streets added for reference (black).
Cell Resolution = 291 m = 955 ft.
Type: Raster/Image. Type: Raster/Image. Type: Raster/Image; Vector/Line.

Scientific Maps


Terrain Elevation (Topography)

Water Resources (Hydrography)


This "digital elevation model" (DEM) gives each pixel a color-coded elevation (black = 90 ft., white = 1302 ft.).
Cell Resolution = 30 m = 98 ft.
Lakes, reservoirs, and streams in blue, over the DEM to illustrate relationship to land forms. Different types of vegetation, e.g. forest, grasslands, agricultural, etc.
Type: Raster/Data. Type: Raster/Data; Vector/Line, Polygon. Type: Vector/Polygon

Demographic Maps





Census 2000 population. Each dot represents 10 people (distributed randomly within census blocks, also shown). Census 2000 average age within each census block, grouped into four categories. Census 2000 average household income within each census block group, grouped into four categories.
Type: Vector/Polygon. Type: Vector/Polygon. Type: Vector/Polygon.

Civil and Political Maps


Streets, Precincts, and Schools

Land Use

Open Lands and Trails

Streets and railroads, voting precincts (blue), and K-12 schools. Different uses of land, e.g. commercial, residential, agricultural, institutional, etc. Open lands (green) and trails (red), and again water(blue).
Type: Vector/Line, Polygon, Point. Type: Vector/Polygon. Type: Vector/Line, Polygon.

Calculated Maps


Non-English Principal Language

School Buffer Zones


Census 2000 population whose principal language is not English, normalized by the total population (applied to census block groups). Schools surrounded by 1500-ft. buffer zones. Analysis of digital elevation model to determine regions that flow into the same stream (in random colors), with streams superimposed (light blue).
Type: Vector/Polygon. Type: Vector/Line, Polygon, Point. Type: Raster/Data; Vector/Line, Polygon.

Course Overview

Because of its diverse applications and multiple data types, learning GIS can take several classes.

First Class: Constructing and Sharing Maps

You will learn to construct maps using GIS data such as the above.

You will discover how to use GIS for exploratory analysis of geographic data.

You will also learn how to export your maps into a number of formats such as PDF or Google Earth, so that it can be shared with others who don't have this GIS software.

The data has been prepared (geographically referenced) in advance so that you can focus on the general skills required to work with it.

Often geographic data is not ready-to-use, and in subsequent classes you learn how to use these different formats.

Table of Geographically Named DataSecond Class: Mapping Geographically Named Data

You will learn to map data from tables that use names for geographic locations.

This includes census data and street address data.

In these simple tables, information about each geographic region is in a single row, viz. its name and attribute data.

This type of data can be geographically referenced by associating it with existing prepared data.

Western Hemisphere with Geographic CoordinatesThird Class: Mapping Geographic Coordinate Data

You will learn about geographic spatial references and how the globe is projected onto flat maps on computer screens and paper.

In the process you'll learn to map another common tabular format for geographic data that uses X-Y coordinates such as latitude and longitude.

The data collected by a Global Positioning System (GPS) receiver is in this format.

This type of data can be geographically referenced by associating it with descriptions of its spatial reference (i.e. how its coordinate system is oriented in space).

Map of Amherst, MA in 1833Fourth Class: Working with Traditional Maps

You will learn how to georeference scanned paper maps, and extract their features into vector layers.

There is still a lot of information in the world that already comes in the form of maps.

If you want to compare it with other sets of data, you can bring it into a GIS so that they can be overlayed.

You can also extract information from the map using editing tools to create new GIS data.

Academic Uses of GIS

There are many different ways that GIS can be used in academic pursuits.

As seen in the previous section, there is a wide variety of data that can be used to build your own maps.

Finding this data and pulling it together in a usable format is typically the largest effort involved in GIS.

For example, data from the Third World or precise historical data can be difficult to come by.

As a result, the most effective academic uses of GIS are:

  1. Faculty research and student thesis projects that are longer term and so may include the development of original data or the pursuit of uncertain data sources.

    (An Economics thesis project utilizing British census data is shown below left.)
  2. A "term map" where students learn to build their own maps over a semester (though it's better if data is identified in advance).
  3. Simple classroom activities that are prepared in advance for students, to allow them to explore an issue with geographic foundations (often these can be prepared with ArcGIS and then deployed with the free ArcReader or the more familiar Google Earth software).
  4. Maps created to illustrate important ideas that are provided to students in lectures or handouts or on-line.

    (For example a map that illustrates the economic and political alignments in the 2006 Mexican presidential election, shown below right.)

The Reference Librarians will be of great assistance in obtaining existing data, and Academic Technology Services can assist you in all of these activities.

Economics Thesis Research Peformed by Joshua Stein

The ArcGIS Software

The ArcGIS software that Amherst College provides has made "desktop GIS" a reality.

Geographic Information Systems have been around for more than forty years, but have become increasingly accessible as computing power has increased.

Amherst College has one of the best GIS available, the Arc products from Environmental Systems Research Institute.

Their newest software, ArcGIS, has made GIS significantly easier than it was even a few years ago.

ArcGIS consists of three primary programs:

  • ArcMap: create, view, and manipulate maps (shown).
  • ArcCatalog: view and organize the various pieces of data that go into making a map.
  • ArcToolbox: convert data from one format to another and perform many types of geographic analyses. 

There are also a large number of extensions, for example for spatial or three-dimensional analysis.

Anyone with a Windows computer can install the free program ArcReader (available from the Software (K:) drive), allowing them to view "published maps" produced by ArcGIS.

ArcGIS is available on all Windows computers in most campus computer labs, as well as on classroom projection computers.

In particular, there is a GIS computer classroom where faculty members can teach students about GIS or other subjects applying GIS, and give them a chance to work on projects with the latest hardware and software.

Faculty and staff can install ArcGIS on any College-provided Windows computer, from the Software (K:) drive.

Laptop (off-network) installation of ArcGIS requires a hardware key.

Free one-year licenses are also available for students taking GIS-related courses or programs; visit this ESRI web site for more information.

Contact Academic Technology Services for more information or assistance.

Additional GIS Training and Resources

There are many other options for learning GIS and extending your knowledge.

Amherst College's license for the ArcGIS software includes a number of online courses prepared by ESRI.

Contact Academic Technology Services for more information or to obtain a license code.

Amherst College maintains a collection of ArcGIS documentation in the form of Adobe Acrobat (PDF) digital books, on the network at

K:\Maps\ArcGIS Books-n-Data\Documentation\ESRI Library


What is ArcGIS A brief overview of the various pieces of software that make up ArcGIS.
Getting Started with ArcGIS A brief guide to ArcGIS.
Using ArcMap A brief guide to the ArcMap component of ArcGIS.
Using ArcCatalog A brief guide to the ArcCatalog component of ArcGIS.
Using Publisher A brief guide to the ArcPublisher component of ArcGIS, and the free ArcReader.
Editing in ArcMap An introduction to editing data in ArcMap.
Using Spatial Analyst A comprehensive introduction to geographic-based calculations.
Using 3D Analyst Describes many of the three-dimensional capabilities of ArcGIS.
Building a Geodatabase Geodatabases are a new format to collect together the data underlying maps.
Maplex for ArcGIS An extension that provides better handling of labels.
Understanding Map Projections A more detailed explanation of map projections.

The K:\Maps folder also contains a great deal of data that can be used as the foundation for your own maps.

The Amherst College Library maintains a web page of GIS resources, including links to the GIS books in the library's collection.

There are a number of tutorials that can be found on the Internet, some of which are:

ESRI also provides a useful collection of tips and shortcuts for the Arc software.


Next: Constructing and Sharing Maps

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