GIS For Dummies®

Chapter 11

Searching for Geographic Objects, Distributions, and Groups

In This Chapter

Knowing why you search for polygons

Searching the right polygons for your needs

Understanding the six methods for locating polygons

Turning found objects into groups

After you put geographic data into the computer, you use GIS frequently to get information derived from the data back out. To retrieve data that best suits your needs, you must know why, where, and how you search for geographic objects (such as roads, rivers, lakes, power plants, and thousands of others) and distributions represented by polygons (such as the range of an animal species or ethnic groups within a nation).

The vast majority of geographic objects that you encounter every day occur in groups. Some of these groups even have specific names. Birds occur in flocks, cattle in herds, trees in forests or orchards, quail in coveys, geese in gaggles, and the list goes on. Beyond the biological groups, glacial features (called drumlins) form in swarms, streets form networks, streams form watersheds, homes form neighborhoods, and many more. People assign special names to groups to provide a handy way to refer to features that look alike, act alike, occur in similar places, are near certain features, or occur in similar patterns or densities.

In this chapter, I show you how to specify search criteria that can yield the results you’re looking for. And after a brief look at common GIS interfaces, I explain the six methods for searching ...