When you’re working with maps there are often parts you want to remove. For example, most maps of South Africa will include Marion and Prince Edward Island, two small research islands more than 2,000km off the coast of mainland South Africa.
In most cases when mapping South African data you do not want to include these two islands. Removing them is simple enough in QGIS. Here’s how.
Resources
This example uses a South Africa map with the islands mentioned included. You can download a copy here. Unzip that and use the .shp file for this example.
Open map in QGIS
Open QGIS and click Project→New in the top menubar.
This will create a new blank working area.
Drag your shapefile into the main working area. You only need the .shp file for this exercise.
You’ll see the map listed in the Layers panel to the bottom left. And you’ll see the map, and the islands, in the main window.
Get into editing mode
To edit the map, click the selection tool in the top menu and then select mainland South Africa. It should look like this.
Now toggle the editing mode. You can either click on the editing button in the top menubar. Or right click on the layer in the bottom left Layers panel and select “Toggle Editing”.
When you enable editing mode you’ll see the various points of the map highlighted.
To remove the two islands to the bottom right of the map, click on the Delete Part icon in the editing menubar. Then zoom in on the parts you want to remove and click inside the borders. You’ll need to click one on each island to remove.
When you’re done, click on the editing tool to de-enable editing. You’ll likely be asked to save your layer, which you should do.
Export your map
You can either just save your project in QGIS for further work or you can export a copy. To export, right click the layer you created and select Export→Save features as and save it in the format you need.