Digitizing Vector Layers

QGIS provides easy-to-use yet very powerful digitizing tools. Digitizing or digitization is a process of encoding map coordinates and attributes in digital form. This allows you to create and edit vector data using various data sources such as text files, paper maps, or satellite imagery. This exercise will guide you through the basic interface of vector digitizing using QGIS.

Creating a new project

1. Open QGIS and create a new project. In the Menu, select File ‣ mActionFileNew New Project.

2. Open Project Properties and click the Coordinate Reference System (CRS) tab. Set the following options.

  • Check the Enable ‘on-the-fly’ CRS Transformation.


On the fly CRS transformation allows you to combine various data layers with different reference system into a single map view.

Loading Vector data

1. Add the waterways.shp vector.

2. Zoom to the extent of waterways.shp. Right click on the layer, select mActionZoomToLayer Zoom to Layer Extent.

3. Create a suitable symbology and color scheme for the layer.

Loading raster data

1. To load raster data, select Plugins ‣ OpenLayers plugin ‣ mActionAddBingLayer Add Bing Aerial layer.


We will use the Bing Aerial layer raster as our primary source for digitizing new features in the vector layer.

Setting options for digitizing

Before we can begin digitizing, we must set the snapping tolerance to a value that allows us an optimal editing of the vector layer geometries.


Snapping tolerance is the distance QGIS uses to search for the closest vertex and/or segment you are trying to connect when you set a new vertex or move an existing vertex. If it is not within the snap tolerance, QGIS will leave the vertex where you release the mouse button, instead of snapping it to an existing vertex and/or segment.

1. To set the snapping tolerance, select Settings ‣ Snapping options. Within the Snapping options window, activate the Enable topological editing by adding a check mark.

2. In the list of layers, add a check mark to the waterways. This activates snapping in respective layer. Set the snapping Tolerance to 10 pixels . Select Apply ‣ OK.


When you start editing the layer, new vertices will snap if it is within 10 pixels of another vertex within the current Map View.

3. Save your project.

Digitizing vectors

We will now start digitizing roads.


This process is called heads-up or on-screen digitizing. This is an interactive process, in which a map is created using a previously digitized or scanned information. It is called “heads-up” digitizing because the attention of the user is focused on the screen.

1. Make sure the waterways and Bing Aerial layers are visible.

2. Zoom-in to a smaller area, where the rivers on the image are visible.

3. Select the waterways layer, right-click and select mActionToggleEditing Toggle Editing. Once the layer is in edit mode, additional tool buttons on the editing toolbar previously greyed-out will become available.


For each feature, you first digitize the geometry, then encode the attributes.

4. To digitize the geometry, click the mActionAddFeatureLine Add Feature, left-click on the map area to create the first point/vertex of your new feature.


For lines and polygons, keep on left-clicking for each additional vertex you wish to capture. When you have finished adding vertices, right-click anywhere on the Map View to confirm you have finished entering the geometry of that feature.

The attribute window will appear, allowing you to enter the information for the new feature. Add the type of feature in the type field and the name of the feature in the name field.


To save your editing session, mActionToggleEditing Toggle Editing and click Save.


In some cases, you will reach the edge of the Map View but you would like to continue adding new vertices. When this happens, use the arrow keys or press the spacebar while using your mouse to pan across the Map View.

The Node Tool

The mActionNodeTool Node Tool provides manipulation capabilities of feature vertices similar to CAD programs. It is possible to simply select multiple vertices at once and to move, add or delete them all together. The node tool also works with on-the-fly projection turned on and supports the topological editing feature. This tool is, unlike other tools in Quantum GIS, persistent, so when some operation is done, selection stays active for this feature and tool.


Basic operations

Start by activating the Node Tool and selecting some features by clicking on it. Red boxes appear at each vertex of this feature. Functionalities are:

  • Selecting vertex: Selecting is easy: just click on vertex and the color of this vertex will change to blue. When selecting more vertices, the Shift key can be used to select more vertices. Or the Ctrl key can be used to invert selection of vertices: if selected already then it will be unselected and when not selected, the vertex will be selected. More vertices can be selected at once when clicking somewhere outside feature and opening a rectangle where all vertices inside will be selected. Or just click on an edge and both adjacent vertices should be selected.
  • Adding vertex: Just double click near some edge and a new vertex will appear on the edge near the cursor. Note that the new vertex will appear on one side, not necessarily on the cursor’s position. Move it as necessary.
  • Deleting vertex: After selecting vertices for deletion, click the Delete key and vertices will be deleted.

The rest of the basic editing tools are explained below:

Icon Tool Purpose
mActionToggleEditing Toggle editing Enable editing of the selected vector layer.
mActionFileSave Save Edits Save your editing session in the currently selected layer. This is different from saving your project.
mActionAddFeaturePoint Add Feature-Point Add point features.
mActionAddFeatureLine Add Feature-Line Add line features.
mActionAddFeaturePolygon Add Feature-Polygon Add polygon features.
mActionMoveFeature Move Feature Move location of a selected feature.
mActionNodeTool Node Tool Activate Node tool functions.
mActionDeleteSelected Delete Selected Delete selected one or more features.
mActionEditCut Cut Features Delete a selected feature(s) from the existing layer and place it on a “spatial clipboard”.
mActionEditCopy Copy Features Place selected feature(s) into the “spatial clipboard”.
mActionEditPaste Paste Features Paste feature(s) from the “spatial clipboard” to the currently selected and editable layer.

Full description of the editing tools and other advanced features available in the QGIS User’s Manual.

5. Finish editing the layer.

6. Save your project.


Remember to toggle mActionToggleEditing Toggle Editing off regularly. This allows you to save your recent changes, and also confirms that your data source can accept all your changes.

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