Digitizing features and editing attributes

Digitizing is the process of capturing areas of rasters (scanned maps, satellite images, etc.) in vector format. Attributes will need to be added to the captured features to properly describe and identify them.

Digitizing in Google Earth

Google Earth has both desktop and online versions. For simplicity, we will use the online version.

In your web browser (Edge/Chrome) go to earth.google.com
Drag and zoom the map to Dominica.
Find an area of interest you wish to capture. Zoom in to this area.
Click on the Add path or polygon icon at the top of the page.
Draw a polygon around the feature/area you wish to digitize by clicking around the feature. To complete the process, double-click when you reach the start point again.
Click Save to project.
Save feature to Local KML file. Google’s vector file type is KML/KMZ.
Name the file.
On the left, under Local KML files, go to the current project and click the option icon (3 dots). Select Export as KML file. This will download the file to your computer.

Try using placemarks instead of polygons to mark points on the map.
Download the KML file.

Open the files in QGIS (drag them to the Layers Panel or add a vector layer).

Convert KML/KMZ to Shapefile in QGIS

Right-click the .kml/.kmz layer in the Layers Panel. Select Export --> Save Featuers As...
In the pop-up window, select Format --> ESRI Shapefile.
For File name, browse to save the shapefile.
Leave CRS as the default EPSG:4326 - WGS 84.
Ensure Add saved file to map is checked.
Leave all other default settings and click OK.

The new shapefile will show in the Layers Panel.

Plugins: Using web maps

QGIS uses plugins to add functionality to the software. One such plugin is QuickMapServices which allows basemaps from Google and other services to be loaded directly in the software.

To install a plugin:

On the menu bar, go to Plugins --> Manage and Install Plugins....
Search for and install the QuickMapServices plugin.

To load Google Maps:

On the menu bar, go to Web --> QuickMapServices --> Google --> Google Hybrid. The Google hybrid map will be added to the Layers Panel.

Digitizing can be done on the web map by following the procedure below. Georeferencing is not needed.

Digitizing scanned maps/rasters in QGIS

Download topographic map

The Layer will need to be georeferenced to appear correctly within the country map.

Load the file into the Layers Panel.
On the menu bar, go to Layer --> Create Layer --> New Shapefile Layer....
Name the file to save the layer to.
Set the Geometry type to Polygon to digitize an area. Point features can be digitized as Point or MultiPoint. Linear features such as paths and boundaries may be digitized as LineString.
Notice that the Fields List already has an integer id to identify each unique feature. Under New Field, add a new string field for the name of the area to be digitized.
Click OK when you are finished.
Ensure the Digitizing Toolbar is active.
On the map layer, zoom to the area to be digitized.
Click the Toggle Editing (pencil) icon.
Click the Add Polygon Feature (green) icon.
Click each corner of the area to draw the polygon. Right click to complete the polygon.
Enter the feature details when prompted.
On the Digitizing Toolbar, click Save Layer Edits.

Updating the Attribute Table in QGIS

You may need to add fields and data to a vector layer’s attribute table. You can add and delete fields, edit data and perform various operations, using the attribute table’s menu. To add a new field and data:

Right-click the layer and select Open Attribute Table.
Click the New field icon.
In the popup dialog box, give the field a name, select an appropriate data type and length. You may also add a comment to describe the field.
Click OK when done.
Enter the desired data into the new field of the attribute table.
Click the Save edits icon.

Adding data from GPS devices

Download GPS data

Add XY Data (GPS data):

Go to Layer menu --> Add --> Add Delimited Text Layer.
Set the following:

Input = FarmCoordCSV file.

Specify the output Name and Location.

X and Y fields = Xcoord and Ycoord, respectively.

CRS = EPSG 2002: Dominica 1945 / British West Indies Grid.

Geometry Definition = Point coordinates.

Click OK to finish the import.
Export the temporary XY event layer to a shapefile.