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Introducing Geographic Information Systems with ArcGIS: A Workbook Approach to Learning GIS, 3rd Edition by Michael D. Kennedy

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A Plan for Digitizing and Transforming
Here we will look at a fourth way of getting graphic information into the computer; it is called “heads-up” digitizing—so named because you look up at the monitor rather than down at a paper map, as in traditional digitizing. In heads-up digitizing, an electronic image of a paper map is made by scanning. In this case the map is the Foozit Court. You will be able to see this image on the screen of your computer. By tracing around the lines of the map with crosshairs (a cursor or pointer, controlled by the mouse), you will be able to automatically supply coordinates to ArcMap.
This process is a little like learning to ride a bicycle: not really hard, but difficult to describe in all its detail (e.g., if the bicycle begins to tip over to the left, turn the handlebars to the left—just a little now—and . . .), so I will simply provide general directions and let you figure out how to digitize mostly on your own.
A caveat: In the process of scanning and then displaying a map systematic error may creep in—since scanners, and particularly computer screens do not maintain exactly the same aspect ratio(height to width) as the paper or Mylar map. It’s something to think about, measure, and correct on the final product if necessary.
The product of your digitizing will be an ArcGIS shapefile. As you know, since we have discussed the nature and characteristics of these elements in the last chapter, a line shapefile is made up of beginning points, ending ...

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