GIS For Dummies®

Table of Contents


About This Book

Conventions Used in This Book

What You’re Not to Read

Foolish Assumptions

How This Book Is Organized

Part I: GIS: Geography on Steroids

Part II: Geography Goes Digital

Part III: Retrieving, Counting, and Characterizing Geography

Part IV: Analyzing Geographic Patterns

Part V: GIS Output and Application

Part VI: The Part of Tens

Icons Used in This Book

Where to Go from Here

Part I: GIS: Geography on Steroids

Chapter 1: Seeing the Scope of GIS

Getting a Feel for GIS

Meeting the GIS Collective

Accumulating geographic data

Adding the right computing power

Providing display and representation

Working with people

Knowing How to Think Spatially

Recognizing the spatial nature of questions

Discovering what’s so special about spatial data

At Least 101 Uses of GIS

Managing business activities

Planning city operations and expansion

Providing protection and emergency services

Land management and conservation

Military and defense-related tasks

A treasure chest of possibilities

Chapter 2: Recognizing How Maps Show Information

Knowing How Maps Represent Geography

Understanding scale

Interpreting symbols

Incorporating symbols into your map

Recognizing the Different Types of Maps

Reading reference maps

Using thematic maps

Grasping the importance of scale

Working with Projections and Datums

Picking the right projections

Good projections depend on accurate datums

Working with Coordinate Systems and Land Subdivisions

Meeting the Universal Transverse Mercator (I know you want to)

Measuring the land

Chapter 3: Reading, Analyzing, and Interpreting Maps

Making Sense of Symbols

Categorizing the space on a map

Understanding levels of measurement

Understanding the relationship between symbology and data measurement

Recognizing Patterns

Identifying random distributional patterns

Finding clustered distributional patterns

Observing uniform distributional patterns

Seeing patterns among dissimilar features

Describing patterns with linear features

Understanding the repeated sequence of shapes

Analyzing and Quantifying Patterns

Knowing your geometry and patterns

Using GIS software for the analysis

Determining the type of pattern

Identifying even more patterns

Interpreting the Results and Making Decisions

Part II: Geography Goes Digital

Chapter 4: Creating a Conceptual Model

Helping Computers Read Maps

Embracing the Model-Creation Process

Defining Your Map’s Contents

Choosing a theme to map

Applying the methodology to any GIS project

Breaking down the data you want to include

Verifying your data’s characteristics

Converting from Map to Computer

Deciding how to represent your map

Weighing the benefits: Raster versus vector

Chapter 5: Understanding the GIS Data Models

Examining Raster Models and Structure

Representing dimension when everything is square

Making a quality difference with resolution

Finding objects by coordinates

Finding grid cells by category

Working with map layers

Linking objects and descriptions

Exploring Vector Representation

Simple forms of vector representation

Complex forms of vector representation

Dealing with Surfaces

Storing surface data in a raster model

Representing surfaces in a vector model

Chapter 6: Keeping Track of Data Descriptions

Knowing the Simple Systems for Tracking Descriptions

Understanding computer-assisted cartography

Using computer-aided design

Exploring raster systems

Working with Tables and Database Management Systems

Structuring simple relational data

Getting more complex with relational joins

Managing data in Vector GIS

Storing data in Raster GIS

Searching with SQL in any GIS

Understanding Object-Oriented Systems

Storing attributes with object-oriented systems

Using object orientation to enhance descriptive information

Knowing the packaging descriptions for different objects

Chapter 7: Managing Multiple Maps

Layering Data in GIS Models

Comparing the Map-Handling Capabilities of GIS System Models

Checking out a hybrid system model

Eliminating pointers with integrated system models

Getting better control with object-oriented system models

Opting for an Object-Oriented Model

Chapter 8: Gathering and Digitizing Geographic Data

Identifying Quality Data

Importing Statistical and Sensory Data

Getting information from GPS data

Using remote sensing to create maps

Collecting field data

Working with census data

Getting Existing Map Data into the Computer

Forms of digitizing

Preparing your map for digitizing

Deciding what to digitize

Cleaning up after digitizing

Building the metadata

Part III: Retrieving, Counting, and Characterizing Geography

Chapter 9: Finding Information in Raster Systems

Creating a Search Strategy

Locating objects on a map

Searching for linear features

Searching for areas and distributions

Using the Software to Perform a Search

Searching in simple raster systems

Searching DBMS-supported raster systems

Counting and Tabulating the Search Results

Getting simple statistics

Interpreting the results

Chapter 10: Finding Features in Vector Systems

Getting Explicit with Vector Data

Seeing How Data Structure Affects Retrieval

Deciding How to Search the Systems

Targeting the right data source

Keeping the expected result in mind

Locating Specific Features with SQL

Getting to the point(s)

Keeping your searches

What’s my line?

Searching Vector Systems using Geography

Counting, Tabulation, and Summary Statistics

Validating the Results

Chapter 11: Searching for Geographic Objects, Distributions, and Groups

Searching Polygons in a GIS

Searching for the Right Objects

Extracting specific information

Knowing the size of each polygon

Working with concentrations of point objects

Reorganizing data

Locating 2-D Map Objects

Searching based on category

Finding polygons based on level

Looking for polygons based on value

Locating polygons based on size, shape, and orientation

Finding polygons based on location and position

Defining the Groups You Want to Find

Looking for common properties

Looking for common positioning

Grouping by what you already know

Part IV: Analyzing Geographic Patterns

Chapter 12: Measuring Distance

Taking Absolute Measurement

Finding the shortest straight-line path

Measuring Manhattan distance

Calculating distance along networks

Working with buffers

Establishing Relative Measurement

Adjacency and nearness

Separation and isolation

Containment and surroundedness

Measuring Functional Distance

Anisotropy (whew!) — non-uniformity

Accounting for physical parameters

Based on intangibles

Creating the functional surface

Calculating the functional distance

Chapter 13: Working with Statistical Surfaces

Examining the Character of Statistical Surfaces

Understanding discrete and continuous surfaces

Exploring rugged and smooth surfaces

Climbing steep surfaces

Determining slope and orientation

Working with Surface Data

Collecting surface data for entire areas

Sampling statistical surfaces

Displaying and analyzing Z values

Ignoring the rules

Predicting Values with Interpolation

Determining values with linear interpolation

Using non-linear interpolation

Estimating values with distance-weighted interpolation

Knowing the other exact interpolation methods

Chapter 14: Exploring Topographical Surfaces

Modeling Visibility with Viewsheds

The importance of viewshed analysis

Using ray tracing

Finding and Using Basins

Knowing how basins work

Working with basins in your GIS

Characterizing Flow

Knowing the importance of flow

Modeling and using flow

Defining Streams

Finding and quantifying streams

Identifying methods that work for you

Chapter 15: Working with Networks

Measuring Connectivity

Recognizing the importance of connectivity

Measuring and using connectivity

Working with Impedance Values

Knowing when your paths are fast or slow

Modeling impedance for traffic flow

Working with One-Way Paths

Understanding unidirectional paths

Modeling unidirectional paths

Characterizing Circuitry

Knowing when lines create circuits

Measuring and modeling circuits

Working with Turns and Intersections

Recognizing the importance of turns and intersections

Encoding and using turns and intersections

Directing Traffic and Exploiting Networks

Finding the shortest path, or route

Finding the fastest path

Finding the nicest path

Finding the service areas

Chapter 16: Comparing Multiple Maps

Exploring Methods of Map Overlay

Finding points in polygons

Finding lines on polygons

Using Logical Overlay to Compare Polygons

Searching with union overlay

Using intersection overlay

Understanding complement or symmetrical difference overlay

Using identity overlay

Comparing geometry with clip overlay

Understanding Raster Overlay

Comparing Features with Selective Overlay

Chapter 17: Map Algebra and Model Building

Creating Cartographic Models

Understanding Map Algebra

The Language of Map Algebra

Performing Functions with Map Algebra

Exercising control

Using local functions

Using focal functions

Exploring zonal functions

Understanding block functions

Using global functions

Formulating a Model

Making a formulation flowchart

Basing your database on your flowchart

Implementing a Model

Testing a Model

Determining whether the software is working correctly

Assessing whether the model gives adequate results

Gauging whether your model makes sense

Ensuring that your model satisfies the user

Part V: GIS Output and Application

Chapter 18: Producing Cartographic Output

Exploring Traditional Maps

Mapping qualitative data

Mapping quantitative data

Creating classes

Using map elements

Factoring in graphic map design

Understanding Cartograms

Attracting attention with area cartograms

Distorting distance with linear cartograms

Mapping sequence with routed line cartograms

Chapter 19: Generating Non-Cartographic Output

Looking for Routings and Travel Directions

Getting Customer Lists and Statistical Data

Producing Alarms and Signals (Audio and Video)

Benefiting from Virtual Output

Animating your maps

Getting the most from flythroughs

Chapter 20: GIS in Organizations

Understanding How Your Organization’s Interactions Change

Categorizing the Types of Organizations That Use GIS




Designing and Introducing a GIS for Your Organization

Understanding how technology affects organizations

Managing people problems

Planning for integration

Looking Before You Leap (And Afterwards, Too)

Performing needs analysis

Performing a cost/benefit analysis

Understanding initial versus ongoing analysis

Using Change Detection

Technological change

Institutional change

Part VI: The Part of Tens

Chapter 21: Ten GIS Software Vendors

Environmental Systems Research Institute

PitneyBowes MapInfo Incorporated


Clark Laboratories

Autodesk, Inc.

GE Smallworld

PCI Geomatics

Leica Geosystems

Bentley GIS


Chapter 22: Ten Questions to Ask Potential Vendors

What Services Do You Offer?

Can You Show How Your Product Will Meet My Needs?

What Data Formats Does Your Product Support?

How Do You Handle Communications and Change Requests?

What Hardware Expertise Do You Have?

What Does the Price Include?

How Long Until the System Is Operational?

What Happens If the System Crashes?

What Are Your Quality-Control Procedures?

Chapter 23: Ten GIS Data Sources

GIS Data Depot

Environmental Systems Research Institute

National Geospatial Data Clearinghouse

Center for International Earth Science Information Network (CIESIN)


Instituto National de Estadistica Geographia e Informatica (INEGI)

CGIAR Consortium for Spatial Information (CGIAR-CSI)

Australian Consortium for the Asian Spatial Information and Analysis Network (ACASIAN)

Geoscience Australia

Canada Geospatial Data Infrastructure

GIS For Dummies®

by Michael N. DeMers


About the Author

Michael DeMers is an Associate Professor of Geography at New Mexico State University and has been teaching GIS-related courses since 1983. He is the author of Fundamentals of Geographic Information Systems (4th Edition), which has been translated into both Russian and simple Chinese, and GIS Modeling in Raster, currently being translated into Arabic.


To all who have taught me, including my teachers, my students, my colleagues, and those I have known only through their writings.


I am grateful to Katie Feltman and Andy Cummings for having the faith in me to write this book. Both gratitude and high praise are due to Colleen Totz Diamond and Laura Miller for their Herculean efforts to make sense of the often vague and always technical GIS ideas and terms. I thank Karen Kemp for her diligent efforts to keep me from technical blunders. My deepest thanks go to Leah Cameron who endured, persevered, and worked tirelessly, all with wonderful humor and constant encouragement. Thanks to all of you in composition, proofreading, page layout, and graphics who convert words and sketches into a polished document. Thanks to Caliper Corporation, Clarke Laboratories, and Intergraph Corporation for providing me with complementary copies of their software (Maptitude, IDRISI, and GeoMedia Professional, respectively) for the production of this book. Finally, thanks to all those I love so dearly who have supported me on this journey.

Publisher’s Acknowledgments

We’re proud of this book; please send us your comments through our online registration form located at

Some of the people who helped bring this book to market include the following:

Acquisitions, Editorial, and Media Development

Editors: Leah P. Cameron, Colleen Totz Diamond, Laura Miller

Senior Acquisitions Editor: Katie Feltman

Technical Editor: Karen Kemp

Editorial Assistant: Amanda Foxworth

Sr. Editorial Assistant: Cherie Case

Cartoons: Rich Tennant (

Composition Services

Project Coordinator: Katherine Key

Layout and Graphics: Shawn Frazier, Nikki Gately, Sarah Philippart, Christin Swinford, Christine Williams

Proofreader: Debbye Butler

Indexer: Potomac Indexing, LLC

Publishing and Editorial for Technology Dummies

Richard Swadley, Vice President and Executive Group Publisher

Andy Cummings, Vice President and Publisher

Mary Bednarek, Executive Acquisitions Director

Mary C. Corder, Editorial Director

Publishing for Consumer Dummies

Diane Graves Steele, Vice President and Publisher

Composition Services

Gerry Fahey, Vice President of Production Services

Debbie Stailey, Director of Composition Services


Do you plan to purchase a geographic information system (GIS) in the near future? Are you curious about what it can do for you and how you can get the most out of it? Do you need to use the software, or do you need to supervise others who use it? Do you have concerns about how GIS might change the way your organization functions?

If you answered yes to any of these questions, GIS For Dummies is the right book for you. GIS is some of the most exciting software to come along in ages, and I want to get you as excited about the possibilities GIS offers as I am. This book can help you start thinking about how you can use maps and harness the awesome power of this new technology.

About This Book

Unlike many books on GIS, this one isn’t meant to keep you spellbound for days or weeks. Instead, you can use this book when you need to answer basic questions or figure out what questions to ask your GIS-specialist friends. Think of this book as a reference you can use to find what you need when you need it.

The book gives you a big picture look at GIS — everything from the parts that make up the systems (see Chapter 1) to the spatial information products (see Chapter 20) that the systems produce. So wherever your interests in GIS point you, find those topics in the Table of Contents or Index and jump right in.

Conventions Used in This Book

GIS terminology can get a bit confusing, especially with computer terms. I use the term raster to represent both a GIS data structure (composed of square grid cells) and the software based on that structure. When I talk about vector, I’m also referring to both the data structure (based on points, lines, and polygons) and software that uses the structure.

When I define a term for you, that term appears in italics. Also, I show URLs in monofont typeface to set them apart from the regular text.

What You’re Not to Read

You may feel the urge, every now and then, to explore some of the more advanced features of the GIS software. The GIS crowd might recognize these features and understand the details, but I don’t expect everyone to have (or want to have) that specialized knowledge. Most GIS analysis is based on pretty basic ideas about how things work in geographic space. Sometimes, GIS gets technical and uses fancier methods including mathematical procedures that you probably don’t need to understand in depth. So, keep an eye out for the Technical Stuff icons and skip them if you want.

Also, I like to illustrate certain points with extra examples that appear in the book as sidebars. I think you’ll find the examples interesting, but they’re not essential to your understanding of the basics.

Foolish Assumptions

I’m going to assume that you’ve heard about GIS but don’t know all that much about its inner workings and hidden mechanisms. Many people think GIS (geographic information system) means GPS (global positioning system) because more people have heard the term GPS. In reality, GPS is just a part of GIS, and I tell you about that in Chapter 8. I assume you have something more than a casual interest in GIS, so I explain what GIS is, what it does, and how it can help you with what you do in your organization. Here are a few other assumptions I make:

You know what a map is. GIS relies heavily on maps and map-related data. I assume that you have used a map of some kind, but aren’t an expert in either making or using maps. I provide all the background you need to become familiar with how maps represent the real-world geography.

You know what geography is. I assume that you’ve taken a geography class at some point in your life, but I don’t assume that you’re a geographer or that you think like a geographer. So I guide you on that path, as well. After you figure out how to think like a geographer (in mapping terms), GIS can become your friend and ally. You might even find it fun to use.

You use some form of computer from time to time. GIS relies on computers. I don’t expect that you’re a computer technician, but I do assume that you know what data files and software programs are and how to use a computer interface. Beyond that, I explain some of the inner workings of the GIS software and databases so that you can ask intelligent questions of the GIS experts.

How This Book Is Organized

GIS For Dummies contains six parts. They move from general background in geography and mapping in Part I, to the use of computers for maps in Part II, GIS data retrieval in Parts III, pattern identification and analysis in Part IV, a look at GIS output in Part V, and some helpful info about GIS vendors and data sources in the Part of Tens (Part VI).

Part I: GIS: Geography on Steroids

If you’re brand new to GIS, you may want to start here. Part I provides a general overview of the book, explains the basic geography background needed to understand how maps represent the real world, and introduces you to some of the mapping terminology that you need to know to understand GIS-speak. It covers map reading, symbolism, projections (moving from 3-D to 2-D), datums (starting points for measurement), scale issues, and generalization. You can see the power of map data and how getting them into your computer really improves your ability to make use of information contain in maps.

Part II: Geography Goes Digital

Part II deals with how you get data from your paper maps into the computer. If you’re unsure about how GIS data work inside the computer, this part can give you the answers. In this part, I show you the two basic models used for digital map representation (grids, called raster; and points, lines, and polygons, called vector). You find out how these different models enable you to keep track of the geographic features you include in your GIS and how the models link these features to the descriptive information that eventually winds up in your GIS output (such as a map legend).

Part III: Retrieving, Counting, and Characterizing Geography

Part III is for people who want to know how to use GIS to answer questions. It includes information about how to find the geographic features that you put in your GIS database, different ways of searching for features, how to count them up when you find them, and how you can describe what you find. In this part, you discover how to locate and characterize features by type or category, by their sizes and shapes, by measurements that describe them, and even by where they’re located relative to each other in geographic space.

Part IV: Analyzing Geographic Patterns

GIS does its most powerful work when analyzing the patterns that you identify, and Part IV focuses on that subject. You see how to measure lengths, areas, distances, and volumes; as well as how to work with networks, such as highways and streets. I explain both topographic and non-topographic surfaces, how to analyze rivers and determine where water will flow during flooding, and how to determine places that an observer can and can’t see from a certain point. I even show you how to combine maps and use a powerful map analysis language called map algebra.

This part can’t make you an expert in GIS analysis, but it can help you figure out enough to start your analyses and talk knowledgeably with the experts.

Part V: GIS Output and Application

In Part V, I show you how to make the most of all your GIS queries and analysis. You can find out about the various types of map output, as well as non-map output, that you can use to help explain the results of your work. I tell you how GIS can generate travel directions, customer lists, alarms, and even movies that show maps through time. Finally, I show you how to smoothly incorporate this high-level technology into your organization so that you can quickly take advantage of its power.

Part VI: The Part of Tens

In the Part of Tens, I introduce ten GIS software vendors and explain what other products and services they provide. I also provide a handy list of questions to ask those vendors before you decide where to purchase software, products, and services. Finally, I also provide a list of sources of GIS data from government and private companies — both free and for purchase.

Icons Used in This Book

GIS For Dummies uses little pictures, or icons, that help direct your reading. These little graphics can save you time by letting you find all the high points quickly.

Tip.eps The Tip icon provides a few helpful hints about shortcuts, best practices, and just plain common sense when it comes to GIS. GIS tips help you do the right things at the right time for the right reasons. Each tip comes with an explanation about why it’s a good idea, too.

Warning(bomb).eps I use the Warning icon to keep you from making mistakes that are very hard to recover from. Unfortunately, GIS doesn’t come with many built-in safety mechanisms, so I try to point out potential problem points.

Remember.eps The Remember icon is sort of like a summary of important points that you need to focus on. In some cases, I remind you of things I cover recently in the chapter, and in other cases, I highlight material from other parts of the book and explain how it applies to that specific discussion. Think of them like tiny refresher courses.

realworld(gis).eps The Real World GIS icon highlights all the places that you can find out how people use GIS to accomplish real tasks in the real world.

TechnicalStuff.eps When you see the Technical Stuff icon, you don’t have to read the technical information to understand the surrounding text — but you might want to look at it and get a sense of all the possibilities of GIS.

Where to Go from Here

Because GIS software changes all the time, the user community requires constant updating and retraining. Many fine community colleges, technical schools, colleges, and universities provide formal education in GIS, and some provide continuing education courses to help you keep up with what’s going on. Some vendors offer face-to-face and online courses (largely geared toward their product line, of course).

You can also keep updated by interacting with other users. In the past, you’d make these contacts through professional meetings, trade shows, and user group meetings (which still draw plenty of users). Today’s technology provides you with a supplemental method of keeping current. Blogs, wikis, forums, and RSS feeds now provide a vast array of methods that you can use to obtain just the right answer in a timely fashion without ever having to leave your computer. Even the vendors themselves often provide audio and video podcasts that give updates on the newest software wrinkles. Here are a few prominent Web-based resources that you can use to continue your GIS education:

GIS Café ( A general online GIS community that contains all things GIS, including forums, data providers, and much more.

GIS Data Depot ( Another general online GIS community which is focused mostly on data sharing.

GIS Lounge ( Similar to GIS Café, but with a somewhat more educational and informational spin.

Directions Magazine ( A forum and online GIS magazine that focuses on keeping the reader up to date on research, innovations, software, and hardware related to GIS.

VerySpatial ( A podcast that generally covers the larger discipline of geography, but with a large amount of GIS content.

ESRI Podcasts ( ESRI’s podcasts include both an instructional series and a speaker series.

GIS forums and podcasts will continue to increase, both in number and in focus. An occasional search on your favorite Internet browser can keep you reading and listening about GIS for a long time to come.

Part I

GIS: Geography on Steroids


In this part . . .

No, I’m not advocating the use of steroids, but I am advocating GIS. In this part, I provide an introduction to all the geography and map-related capabilities that underlie the enormous power of GIS. You find out how GIS has merged the speed and strength of a computer with a geographer’s robust toolkit. And even more impressive, you see how this merger has produced one of the most transforming technologies of the 21st century.