Geography Reference
In-Depth Information
ultimately a hard-copy map), Harrison would like to label the lakes. He
could just use a paint program and label the lakes, but then he would
have to modify the original image. Besides, Harrison tends to flip-flop
a bit about what he wants, so maximum flexibility is important. Harri-
son then discovers the notion of creating his own vector data. If you're
not familiar with it, vector data is just points, lines, and polygons that
represent real features on the ground. Harrison thinks about creating
a point near the middle of each lake and labeling it, but that would
look a bit goofy, even for him. He then decides to digitize each lake and
make a polygon. For each polygon, he'll add an attribute—the name.
While Harrison is busy working on his lakes, let's talk briefly about the
process of digitizing.
In the simplest sense, digitizing is tracing features with your mouse. In
reality, there is a fair bit of skill involved in doing it right. The process
goes something like this: you create a new layer (think file for now) to
store your features in, add some attributes to it (for example, the lake
name), and then begin tracing features. As you complete each feature,
you enter the attributes. When you are done, you have a layer you
can view and label using the attributes you entered. Of course, this is
a simple explanation, but all digitizing is really an extension of these
concepts.
We've kind of lumped things together under the digitizing category.
There are other ways to create new data apart from digitizing. Harrison
actually illustrated this for us when he imported his GPS data. Other
ways to create data include importing from a text file, scanning images,
and even accepting coordinates from a web form. We'll get into more of
this later. Let's hope by now both you and Harrison have a good idea of
just what it means to create GIS data. Once we have all this good data,
it's time to analyze.
Analyze
This is where GIS really shines. Being able to use our data we worked
so hard on collecting to answer some what-if questions is what makes
GIS exciting. This is also what separates GIS software from being just
a “viewer.”
Using GIS we can answer all types of questions. Let's get Harrison to
help us out with an example. He has a theory that most of his bird
sightings are within 200 feet of a lakeshore. With all his hard work,
Harrison can view both his bird sightings and the lakes, but he can't
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