Introducing Geographic Information Systems with ArcGIS: A Workbook Approach to Learning GIS, 3rd Edition

The Original Form of Spatial Data: Maps

Thirty years ago spatial data meant maps. A single map is a spatial database and, for many purposes, a very good one. For hundreds, perhaps thousands, of years, almost all of the information used to support land-related planning and management, and myriad other activities such as navigation, has come from maps. Mapmaking became a well-developed activity. The piece of paper on which the map is drawn is a continuum that can represent the quasi-two-dimensional surface of the Earth in an obvious way. (“A picture is worth a thousand words.”) Many times when people are asked “How do I get to . . . ?” they respond, “Let me draw you a map.”

Why, then, should we spend millions of dollars on databases composed of discrete symbols when maps are available? Among the answers are that maps alone are extremely hard to use for many of the analyses that human activity requires. There are precious few ways to combine graphic information with other graphic information. Decisions involving the space we live in are becoming more difficult all the time because of the larger number of factors that must be considered. Physical techniques have been evolved for combining maps, such as overlaying one transparent map with another and looking through the composite, but these methods are tremendously time-consuming and have substantial limitations in terms of useful output.

The reason spatial databases composed of discrete symbols (numbers, letters, and special characters) ...