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GIS Defined

The maturing of the computer age has greatly changed the manner in which we can merge, compare, and manipulate multiple maps and other data sets,. Computers and their software have significantly enhanced data handling capacity and flexibility. A powerful new tool, known as the Geographic Information System (GIS) emerged in the 1970s. Many of those who developed GIS were inspired by the classic 1969 publication of Design with Nature by Ian McHarg (Doubleday/Natural History Press), a leading landscape architect then at the University of Pennsylvania. This document pointed the way to planning and decision-making through comparative, integrated maps and related data types. Since its inception, GIS has become a major growth industry, now conducted worldwide at the multi-billion-dollar level. It has blossomed into the main way for using maps (novel and practical) in most endeavors that focus and rely on geographically-based data of many kinds. Because remote sensing has routinely provided new images of the Earth's surface, it too has become intertwined with GIS as a means to constantly and inexpensively update some of the GIS data (such as land use and cover). The Association for Geographic Information defines GIS as:

A system for capturing, storing, checking, integrating, manipulating, analyzing, and displaying data which are spatially referenced to the Earth.

A simpler working definition is: A computer-based approach to interpreting maps and images and applying them to problem-solving. The inclusion of computers to store, process, manipulate, interpret, and display GIS information is the critical ingredient that separate modern GIS from the more conventional (traditional) methods of using maps and correlative data prior to the 1970s.

15-6: In their book on GIS, J. Star and J. Estes (see references at the end of this section) mention the four essential "M's" involved in the use of GIS by planners, resource managers, scientists, and others. These are operations that are commonly carried out in succession. Try to guess what these M's are. ANSWER

We synopsize the role of GIS in the general planning process for site selection, environmental management, and other geographically-dependent applications in this diagram:

GIS in the Planning Process diagram.

From B. Davis, GIS: A Visual Approach, ©1996. Reproduced by permission of Onword Press, Santa Fe, NM.

The driver for this closed-loop operation is the constant need for timely information about human activities and expectations concerning life in the real world. The specifics underlying those needs define the types and amounts of data/information required. Once GIS users stipulate the specifics, they collect the data from multiformed sources, such as already published maps and tabulations, current field observations, surveys, and aerial/satellite imagery. In the next step they convert the varied data into computer-compatible formats. The heart of the GIS operation lies within various techniques for analysis that users have devised as GIS evolved. They then present their reports, displays, new maps, statistics, and other kinds of computer-based, information-oriented products to decision-makers. The test of value then happens by applying the results in the same real world that dictated the initial requirements. Data management through a GIS involves all of these facets:

GIS Data Management diagram.

15-7: What is the "driver" or key determinant in the above Data Management diagram? ANSWER

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Primary Author: Nicholas M. Short, Sr. email:

Collaborators: Code 935 NASA GSFC, GST, USAF Academy
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