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. 2. Open Project Properties and click the Coordinate Reference System (CRS) tab. Set the following options. A Raster dataset is composed of rows (running across) and columns (running down) of Pixel s (also know as cells). Each pixel represents a geographical region, and the value in that pixel represents some characteristics of that region. Images with a pixel size covering a small area are called ‘high resolution’ images because it is possible to make out a high degree of detail in the image. Images with a pixel size covering a large area are called ‘low resolution’ images because the amount of detail the images show is low. We will now create a new vector layer, to digitize roads. We will use a line layer to represent this data. 4. In the New attribute, add name in the Name field and choose Text data as the data type. Then, click Add to attributes list. The newly added attribute field is added in the list. 5. Add another attribute column. In the New attribute, add type in the Name field and choose Text data as the data type. Then, click Add to attributes list. In the name attribute field, we will encode the name of the feature. In the type attribute field we encode the type of road (either primary, secondary, residential, etc.). Click OK. 6. A new window will appear for the filename and location of the data within your directory. Use the filename, quiapo_roads.shp. 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. 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 quiapo_roads. This activates snapping in respective layer. Set the snapping tolerance to 10 map units for quiapo_roads layer. Select Apply –>, OK. When you start editing the roads layer, new vertices will snap if it is within 10 map units or 10 meters of another vertex. 1. Make sure the quiapo_roads and Bing Aerial layers are visible. Click the checkbox preceding the name of the layer in the Map Legend view to hide/show layers. 3. Select the quiapo_roads layer, right-click and select Toggle Editing. Once the layer is in edit mode, additional tool buttons on the editing toolbar previously greyed-out will become available. 4. To digitize the geometry, click the 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 road in the type field and the name of the feature in the name field. The 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. 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: Full description of the editing tools and other advanced features available in the QGIS User’s Manual. Source.