GIS Defined - Completely GIS, GPS, and Remote Sensing Tutorial - facegis.com
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 (capture, integration, 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 1969 publication of the classic 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.

McHarg's book inspired a young geographer, Jack Dangermond, to become one of the pioneers in GIS. He founded a company, ESRI, that has since become a world leader in this field. Dangermond came to NASA Goddard in the early 1980s to demonstrate this newly emerging technology to staff of ERRSAC, including the writer (NMS) at the time. He started with the basics. His "pitch" was remarkable - I was converted into an "instant fan". The case study he used - getting an activist group of citizens in northwest Colorado to agree on a master plan to develop the region - was totally convincing. My one regret is that my work mission never brought me into a full use of GIS, other than peripherally during the nuclear power plant project described later in this Section.

ESRI has grown into the world leader in GIS technology and applications. A 2007 review of how ESRI's main product is applied is given by Jack Dangermond on an ESRI website.

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' (usually) land surface.

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.

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

Integration of Landsat data with other sources to derive data elements input to a GIS interpretation model.

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 multiple 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 (often, themselves). 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.

Source: http://rst.gsfc.nasa.gov