GRASS Basics - Desktop GIS: Mapping the Planet with Open Source Tools - page 317

Figure C.13: Results of digitizing lakes in GRASS
will pop up, and we can enter Lake Tanganyika for the name. When we
submit, the attributes are stored. Now when we click the centroid of the
lake in the GRASS map display using the Query tool, we get the polygon
attributes. In fact, now our africa_lakes map contains two feature types:
1_line and 1_polygon . We can draw boundaries to view the outline of the
lake. If we also turn on areas in the GIS Manager, we see the polygon.
In Figure C.13 , you can see the results of our digitizing the lakes. We've
rendered them in cyan with a three-pixel dark blue border and added
labels to the centroids, all using the GIS Manager to set things up.
That completes our simple example of digitizing in GRASS. We didn't get
too fancy with things but illustrated a fairly typical session for creating
polygons. Of course, lines and points work in a similar fashion. The
other tools on the v.digit dialog box allow us to add and delete a vertex,
split a line, and move or delete an entire feature.
On the upper toolbar, you'll find tools to both display categories for
a feature as well as copy them. Why would you want to copy cate-
gories from one feature to another? Well, imagine we have two fea-