GRASS GIS Manual: wxGUI Raster Digitizer

Note: This document is for an older version of GRASS GIS that will be discontinued soon. You should upgrade, and read the current manual page.

wxGUI Raster Digitizer

KEYWORDS
DESCRIPTION
NOTES
EXAMPLES
SEE ALSO
AUTHOR

KEYWORDS

display, GUI, raster, editing, digitizer

Raster Digitizer is a simple tool to quickly to draw lines, areas, and circles and save these features in a raster map. It is accessible from 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