As a tool-kit for answering geographic questions the GIS currently provides a relatively robust set of computer algorithms. But as our application needs increase and our knowledge of geographic concepts grow, the need for even more advanced tools increases. Recognizing this increased need for advanced tools and new theory development, the GIS industry pays a premium for graduates who know not only how to use the existing software in complex and innovative ways, but how to push the technology beyond its current bounds. This new method of inquiry, known as geographic information science, demonstrates that a knowledge of the various GIS software packages is no longer sufficient if the industry is to expand. It acknowledges that many algorithms commonly used in GIS are either approximations of geographic reality or are workarounds stemming from a lack of understanding of the underlying geographic principles driving spatial patterns and dynamics.

This textbook is designed to provide some of the basics required not only to operate currently available GIS technology to solve everyday geographical problems, but also to encourage spatial thinking in the broader context. A fundamental premise of GIS is that its users, as well as its designers and developers, must be able to identify and isolate the spatial components of their knowledge domains. Before spatial models can even be considered, much less implemented, we must be able to recognize that geographic space is the underlying fabric upon which all spatial models are embroidered. While this may seem to be commonly accepted in theory, in practice it is not always so well recognized. For example, it is not uncommon for business owners to be unaware that the potential for customers is generally greater among those who live near the business than for those who live farther away. This is a fundamental concept involved in economic placement theory-a type of modeling commonly applied within GIS. Even for those that recognize that there is an important spatial component inherent within their academic disciplines, their education frequently delays the explicit inclusion of that spatial component until late in the student's academic course work, thus limiting their exposure to severely restrained amounts and types of spatial data and spatial concepts.

Fortunately, this situation is changing, with new sub-fields developing that not only acknowledge but which focus on the importance of geographic space within their subject. The new sciences of landscape ecology and conservation biology, for example, often contain an explicit spatial component. Health care professionals are now examining the spread of disease vectors, the placement of health care facilities, and the importance of spatial interactions as they affect overall health of patients. Agriculture is now attempting to link ground-based data with remotely sensed data to examine the potential to increase the efficiency of applications of fertilizers, water, and pesticides under the heading of 11 precision agriculture." Even the U.S. Department of Justice's newly formed Crime Mapping Research Center is a direct result of the acknowledged need for mapped data in the analysis of crime statistics for reducing crime and apprehending criminals. Within that context, a new field of study called geographic profiling has developed to analyze the spatial behavior of serial criminals, allowing criminologists to predict the locations of future criminal events. Investigative journalists are beginning to use GIS as a method of answering questions about everything from the differential affects of storm damage to the impact of terrain and weather on military operations. The GIS literature within wildlife science is still another example of the exponential growth of GIS models applied to and developed by practitioners in other subject disciplines.

Although there are many additional examples of how spatial thinking has led directly to the use of GIS in a wide variety of fields, there are many more potential applications yet to be discovered by people trained in geographic information systems and geographic information science. For those whose career goals are primarily to become GIS technicians, it is important to understand how the GIS is to be used for modeling so that the databases allow the users to perform the necessary tasks. Applications specialists need to understand both the spatial nature of the data they will most often encounter as well as the limitations of the data structures and data models used by the GIS to allow them to do so. Finally, GIS designers and developers need to know what spatial analytical needs are not being met, the limitations of existing algorithms and data models, and how the users can best interact with the software. They must also be well versed in software development techniques and computer science.

This presents quite a diverse audience for those reading this book and/or taking perhaps their first course in geographic information systems. But while I have attempted to include some basic material of interest to all of these groups, I have focused on the primary task of the GIS-analysis and decision making. Analysis is what links the technician who must perform the analytical functions, the applications specialists who need the analyses performed, and the developers who must make this happen. The text is meant as an overview of the discipline at a basic level, not as an encyclopedia of existing knowledge or as an examination of new theory. My intent is to provide a set of basic concepts upon which students will, through the pursuit of additional course work and practical experience, develop new applications, new theory, and new software.

For this second edition I have tried to incorporate as many of the suggested changes we received from readers and reviewers of the first edition to improve readability and the ability to convey the basic concepts. I have made some adjustments in the organization of the text without completely reworking its basic structure. Among the most requested changes is the inclusion of more graphics. I have added close to 40 new graphics to try to link the concepts to a visual learning device. I've also tried to improve or replace some of the graphics that were described as less than useful. All of the changes, whether major or minor, have been in response to the needs expressed by both instructors and students.

As you read through the book, whether as part of a formal GIS course or independently, try to examine each concept as it applies to your own career goals. Look for the spatial components and how they are represented and modeled. Think beyond the text itself by combining your own interests and background to extend the basic ideas to satisfy your own needs. Be creative. Much of what you read here may not be true in the future. You, and many others like you, will change the way the science, the technology, and the applications will appear in the next decade.

Finally, I invite all of you to become geographers, if not by vocation then by avocation. GIS is about geography and about thinking geographically. Beyond being an essential component of GIS, geography also opens new avenues of examining and analyzing the world around us. More importantly, it provides us with a totally new appreciation of everyday life and the environment in which we live it.

Acknowledgments

I am deeply grateful to the many students, faculty, and reviewers who have suggested changes for the second edition. Unfortunately, there are far too many of you to mention. Please know that I took all your suggestions to heart and that I am grateful to you for helping to make this second edition better than the first. Some of you made substantial efforts on behalf of the second edition, and I would like to thank you by name. First, Dr. Keith Rice (University of Wisconsin, Stevens Point) provided some of the most precise pedagogic insights. He is joined by Dr. Lin Liu (University of Cincinnati), Dr. Donna Peuquet (Pennsylvania State University), and Dr. Elizabeth Wentz (and her students at Arizona State University). Dr. David Cowen (University of South Carolina) was not the only one but was certainly the most vociferous in his recommendation that more graphics be included. While at New Mexico State University, Dr. Howard Holt and Mr. Damian Kessler provided many needed changes and spotted some of the hard to find errors that slipped past me in the first edition. To these colleagues, and to the editorial and production personnel at Wiley, I owe a substantial debt.