Getting the Most Out of QGIS and GRASS Integration - Desktop GIS: Mapping the Planet with Open Source Tools - page 204

Creating a New Map
What if we want to create a new GRASS vector map and add data to
it? We could pop out to the GRASS command line or GUI and do it, or
we can use the Create a new GRASS vector item from the GRASS plugin
menu in QGIS. Before you can do this, though, you have to open the
mapset where you want the new vector map to live.
The steps involved in creating a new GRASS map are as follows:
1. Open the mapset where the map will reside.
2. Click the Create a new GRASS Vector menu item.
3. In the New Vector Name dialog box, enter the name for the new
map.
4. Click OK.
5. Add features to the map using the edit tools.
When you create a new layer, the edit tools automatically pop up so you
can add features. QGIS doesn't add your new map to the canvas yet,
so it may be a bit confusing as to what you are doing. Don't worry—the
layer will show up once we close the edit tool dialog box.
When first created, the layer has only one attribute: cat . Let's say we
are creating a new map named water_wells . This map will contain the
point locations of water wells, and we will digitize them off a raster map
we have showing the locations. Having only the cat attribute by itself
isn't very useful when it comes to storing information about the wells.
We need some additional information, such as owner name, depth, and
whether it's an active well. To do this, we use the Table tab in the edit
dialog box.
In Figure 12.5 , on the next page, you can see the table I constructed for
the water wells map. To build the table, you just use the Add Column
button to add a new column and then give it a name and set the type
and length as appropriate. You can see in the figure I added the owner ,
depth , and active fields. For the active field, I chose to use a single
character that will contain a “Y” or “N” to represent yes or no. Once
everything is set up, clicking the Create/Alter Table button saves the
changes. We can now digitize the wells and add the attributes we need.
We'll start by adding a new well within the Quantum GIS City polygon
and assigning the owner as the city, depth of 220, and a Y in the active
column to indicate it is in use. From there, you can go forth in like
fashion and digitize all the water wells.