On Thursday 28 February 2008, Philipp Steigenberger wrote: > Hi > I want to work with r.plane and r.lake to get simulate floodings in DTMs. > > In the section of interest there is a river which runs from about SSW to > NNE. For r.plane I need the > azimuth. Is there a tool in GRASS which tells me the angle between two > points I mark on the map like I can measure in between two points with > d.measure? > >
Simple trigonometry is a start. Or on a computer the atan2() function is useful: atan2( (end_y - start_y) , (end_x - start_x) ) * 180/pi will return the angle in degrees. The above example is from R, but the C implementation should be similar. Check your local documentation. It shouldn't be hard to add something like this to d.measure for interactive estimation of bearings. On a related note, I wrote a module for GRASS sometime ago called d.bearing which would create a transect from a starting point, a bearing, and a distance along the resulting line. I will dig the source out and see if it still compiles. It might be useful to combine that functionality with what you are talking about. Dylan -- Dylan Beaudette Soil Resource Laboratory http://casoilresource.lawr.ucdavis.edu/ University of California at Davis 530.754.7341 _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
