|
wxGUI Vector DigitizerDESCRIPTIONThe vector digitizer is a wxGUI component intended for interactive editing and digitizing vector maps (see v.edit for non-interactive vector editing GRASS capabilities).Note that only vector maps stored or generated in the current mapset can be opened for editing. The digitizer allows editing of 2D vector features (points, lines, centroids, boundaries, and areas). Vector features can be selected by mouse (bounding box or simply by mouse click, see select threshold in Settings→General→Select threshold), or by query (eg. by line length, see Settings→Query Tool). STARTING THE DIGITIZERThe vector digitizer can be launched from Map Display toolbar by selecting "Digitize" from Tools combobox. Vector map is selectable for editing from Digitizer toolbar ("Select vector map" combobox, note that only vector maps from the current layer tree in Layer Manager are listed). The vector digitizer can alternatively be activated from the contextual menu in the Layer Manager by selecting "Start editing" on selected vector map in the layer tree, or directly from the Layer Manager toolbar . The vector digitizer also can also be launched from the command line as a stand-alone application g.gui.vdigit.CREATING A NEW VECTOR MAPA new vector map can be easily created from the digitizer toolbar by selecting "New vector map" in "Select vector map" combobox. A new vector map is created, added to the current layer tree in Layer Manager and opened for editing. "Select vector map" combobox in the digitizer toolbar also allows easily switching between vector maps to be edited.EDITING AN EXISTING VECTOR MAPAn existing vector map selected in the digitizer toolbar in the "Select vector map" combobox. This map is then opened for editing and added to the current layer tree in the Layer Manager. This "Select vector map" combobox in the digitizer toolbar also allows to easily switch between vector maps to be edited.USING A RASTER BACKGROUND MAPIn order to digitize from a raster map, simply load the map into the Map Display using the Layer Manager. Then start digitizing, see below for details.USING A VECTOR BACKGROUND MAPThe vector digitizer allows you to select a "background" vector map. Loading it within the digitizer is different from simply loading it via Layer Manager since direct interaction with single vector features then becomes possible.Vector features may be copied from the background map by "Copy features from (background) vector map" tool from the "Additional tools" of the digitizer toolbar. Newly digitized vector features are snapped in the given threshold to the features from the background map. DIGITIZER TOOLBAR
NOTES
Dead (deleted) features are only marked as ’dead’ in the geometry file but remain there and occupy space. Any vector module used afterwards on this vector map which really reads and writes vector geometry (so not g.copy) will write only features which are ’alive’. Added or modified vector features are snapped to existing vector features (Settings→General→Snapping). To disable snapping set the snapping threshold to ’0’. If the digitizer crashes for some reason, the changes are automatically saved. Broken topology can be repaired by running v.build. GRASS GIS uses a topological vector format, meaning that a common boundary of two polygons is only stored once. When digitizing polygons it is thus important to be able to only draw each boundary once. When drawing a polygon adjacent to an existing polygon, one has to first split the existing boundary at the points where the new boundary will be attached. Snapping should be set to ensure that the new boundaries are automatically attached to the chosen points. REFERENCES
SEE ALSOwxGUIwxGUI components v.edit, v.category, v.build, wxGUI.rdigit See also the WxGUI Vector Digitizer Wiki page including video tutorials. AUTHORMartin Landa, FBK-irst (2007-2008), Trento, Italy, and Czech Technical University in Prague, Czech RepublicSOURCE CODEAvailable at: wxGUI Vector Digitizer source code (history)Main index | GUI index | Topics index | Keywords index | Graphical index | Full index © 2003-2021 GRASS Development Team, GRASS GIS 7.8.6 Reference Manual
Visit the GSP FreeBSD Man Page Interface. |