Digitizing and Editing Vector Data - Desktop GIS: Mapping the Planet with Open Source Tools - page 70

Chapter 5

Digitizing and Editing Vector Data

One of the strengths of desktop GIS is the ability to create new data.
Although your favorite desktop application can be a data consumer, it
can also be a creator. In this chapter, we'll look at creating vector data
and some of the reasons why you might want to do so.

5.1 Simple Digitizing

If you remember Harrison's original bird project, one of the things he
wanted to do was create a new vector layer for the lakes in one of his
birding areas (see Figure 1.3 , on page 19 ) . Once he had the lakes in a
new vector layer, he could do some more advanced GIS processing to
create a buffer and test his hypothesis regarding birds and nearness
to lakes. This is a pretty simple digitizing project, one that we'll do for
Harrison.

Picking a Tool
As you've gathered, we could use a bunch of tools to digitize the lakes.
Since we're going for simple here, either uDig or QGIS is a good choice.
You could use OpenJUMP or GRASS as well. Since we are going to
do some geoprocessing with this layer (a fancy way of saying create
a buffer), it makes sense to create it in a flexible format that we can
import into whatever application we choose. The obvious choice is a
shapefile, although we could just as easily have chosen PostGIS—but
since we won't talk about that until Chapter 7 , Spatial Databases, on
page 98 , we'll keep it simple.

To build Harrison's layer, we'll use QGIS and create a shapefile con-
taining lakes as polygons.