How to digitize new vectors

By John Lindsay, Ph.D. (Last modified, July 2013)

On-screen digitizing is useful for specifying points of interest for watershed delineation, viewshed analysis, creating ground control points (GCPs) for image rectification and many other common GIS operations. Whitebox's on-screen digitizing has been purposely designed to be very simple and straightforward. In Whitebox, on-screen digitizing is accomplished using the following work flow:

  1. Display a base file, i.e. a raster or vector file, so that the active map area contains a valid geographic extent.
  2. Open the Create New Shapefile tool from the Tools tab. Give your newly created empty shapefile a logical name and specify its shape type (e.g. point, polyline, polygon, etc.). Note, a separate shapefile is required for each shape type, i.e. a shapefile can only contain features of a single shape type. This is a limitation of the shapefile format. If you wish to digitize multiple shape types, e.g. points and polylines, then multiple shapefiles should be created as this stage.
  3. Once the new shapefile has been created, it will be automatically added to the list of displayed layers under the Layers tab. The vector does not currently contain any features so nothing will be displayed in the map area for it. Make sure that the layer has been selected as the active layer.
  4. If you wish to add entries to the shapefile's attribute table, this can be accomplished by selecting the View Attribute Table button from the toolbar and Add New Field from the Edit Fields menu.
  5. The new shapefile should have automatically been selected for editing. If this is not the case, select the Edit Vector button from the toolbar or the corresponding item from the Tools menu.
  6. Select the Digitize New Feature button from the toolbar or the corresponding item from the Tools menu. You will be prompted to enter values for the each of the new feature's attributes.
  7. Once you have entered each of the attributes associated with the new feature and pressed OK, you will be able to digitize the new feature by clicking on the map area. For point base shape type vectors, a single-click is all that is needed to digitize new features. For line and polygon base shape type vectors, each node in the feature is specified by single-clicking on the map area and the feature can be closed by double-clicking. In the case of polygon features, double-clicking will close the feature such that the first and last nodes are connected by a closing arc. The feature will be drawn on the screen as you digitize.
  8. Individual features can be removed from vectors by selecting the feature of interest (while in the 'Select Feature' mouse mode), and then pressing the Delete Feature button or the corresponding item from the Tools menu.

New features can be added and removed from existing shapefiles using the same method. At present there is no means of modifying the position of individual nodes within features, but this functionality is being actively developed.