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GIS For Dummies® by Michael N. DeMers

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Chapter 12

Measuring Distance

In This Chapter

Measuring absolute distance

Calculating relative measurements

Figuring out distance based on function

You can measure anything you put on a map. You use map measurements to figure out how far you are from one place or another, how much land you own, how much ore you might expect to get from a new mine, and many other measurements. You can measure heights, widths, depths, lengths, areas, and volumes. You can also compare measurements as ratios — for example, ratios of length to width, perimeter to area, or height to distance.

Measuring geographic features is one of a GIS’s strengths, and it does the measuring very quickly! Because you can measure many features quickly, you can use those measurements to help you make decisions about what route to take (by comparing distances between features), whether one place is better than another for mining (by calculating the volume of a specific feature), or where you’re likely to find the best ski slopes (by evaluating a feature’s height against its length).

In this chapter, I show how GIS gives you the power to measure all sorts of features. First, I explain the measurements that GIS software generates by default (such as grid cell size), and then I describe how the GIS uses these numbers to calculate other measurements (such as distance between objects). I also tell you about the difference between relative and absolute measurements, and when you might want to use each. I explain how you can ...

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