Working with Vector Data - Desktop GIS: Mapping the Planet with Open Source Tools - page 33

Figure 3.4: Countries classified by population

The results of the classification are shown in Figure 3.4 . As you might
have suspected, China and India are rendered as the most populous,
followed by the United States. We could refine our classification to get
a finer-grained view of population by changing the number of classes
or the method. This is a common way to render data to make it tell a
story. Some of the other OSGIS applications we will look later offer even
more ways to symbolize your data.

3.3 Looking at Attribute Data

In the previous section, you might have wondered how we knew about
the POP_CNTRY field in the world_borders shapefile. Well, there are a num-
ber of ways to examine the attribute data associated with a layer. One of
the quickest ways is with ogrinfo , a utility that is part of the GDAL/OGR
suite. We'll take a more detailed look at ogrinfo and friends later in Sec-
tion 11.2 , Using GDAL and OGR, on page 186 . If ogrinfo is not already
on your system, see Section B.7 , FWTools, on page 295 for information
on installing FWTools. 3

FWTools is a suite of tools that contains many applications, including ogrinfo .

3.