KEYWORDS
display, GUI, raster, editing, digitizer
DESCRIPTION
Raster Digitizer is a simple tool to quickly draw lines, areas,
and circles and save these features in a raster map. It is accessible
from the Map Display toolbar (from the combo box on the right).
Raster Digitizer currently allows you to:
- draw polygons, lines and points
- set category value of the feature you are drawing
- set feature width (width of currently digitized line or diameter of a digitized point in map units)
- create a new raster from scratch or from an already existing raster
- undo edits and save edits before leaving the digitizer
The typical workflow includes these steps:
- Set computational region as needed.
- Switch to Raster Digitizer and select a map to create.
Select either a new raster or create a new raster from existing raster,
also select raster type (CELL, FCELL, DCELL)
- Specify category value and width before drawing a feature
- Specify digitizing tool (area, line, point)
- Start digitizing and when you want to finish area or line, use right click
- Change color of temporary overlay depending on your needs
- Set different category and repeat
- At any point you can use Undo or Save
- If existing raster is used for the new raster, digitized areas will respect
the color table, but you can always set different color table.
NOTES
Raster Digitizer respects computational region including the currently set resolution.
EXAMPLES
In the following figures we start with elev_lid792_1m raster map in North carolina sample dataset
and digitize two buildings, one rectangular and one with circular footprint.
Both buildings have the roof level at 130 m. We set the width when digitizing the point to 50 meters
which results in the building having 50 m in diameter.
When we are done with digitizing, we save the result and explore cast shadows of the buildings with
r.sun module:
g.region raster=elev_lid792_1m
# now create elev_edited raster by digitizing and save
r.slope.aspect elevation=elev_edited slope=elev_slope aspect=elev_aspect
r.sun elevation=elev_edited aspect=elev_aspect slope=elev_slope beam_rad=beam day=172 time=6
Figure: Steps to digitize new buildings on elev_lid792_1m raster map.
SEE ALSO
wxGUI
wxGUI components,
r.in.poly (backend of digitizer),
g.gui.vdigit
AUTHORS
Anna Petrasova, NCSU GeoForALL Laboratory
Tomas Zigo (standalone module)