Digitizing and Editing Vector Data - Desktop GIS: Mapping the Planet with Open Source Tools - page 71

Figure 5.1: Creating a new shapefile in QGIS

Digitizing the Lakes
The first step is to fire up QGIS and add the raster we want to digitize
from to create the lakes. We're using o48092d8.tiff , a DRG from the Daley
Bay Quadrangle in Minnesota. 1 Once we have the raster loaded, we
need to create a new vector layer for the lakes.

As of version 0.9, QGIS supports the creation of shapefiles only for
editing, although you could create a new PostgreSQL layer using SQL
and edit it. For now we'll create a shapefile with an id field and a name
field. To do this, choose New Vector Layer from the Layer menu. In Fig-
ure 5.1 , you can see the completed layer information with the fields
defined. Even though there is a drop-down for file format, there is only
one choice, as we mentioned before. Once we click the OK button, QGIS
opens the dialog box to save the file. This allows you to navigate to the
directory where you want the shapefile to live and give it an appropriate
name. Having done that, our shapefile is created and displayed in QGIS
as shown in Figure 5.2 , on the next page. Of course, there is nothing in
it yet.

Now we are ready to digitize. First we need to allow editing on the new
layer by right-clicking it in the legend and choosing Allow Editing from

Available at http://www.archive.org/download/usgs_drg_mn_48092_d8/o48092d8.tif .

1.