Thank you Hamish for these suggestions, I'll probably dig in the database direction, in order to create a labels layer, easy to add in the postscript composition.
Bye, Vincent Le jeudi 27 octobre 2011 à 21:51 -0700, Hamish a écrit : > Vincent wrote: > > a bit of squeezed with ps.map : is there a simple way to > > draw arrowheads on top of vector lines in a map composition ? > > you mean like 'd.vect disp=dir' ? if so, not that I know of. > > > I did not find any option in vlines instruction. Did I miss > > it ? > > > > Perhaps should I extract tnodes (or fnodes) from the source > > lines vector, then print arrowheads as symbols with vpoints > > instruction. > > you should make a new ">" symbol without a tail in case the > rotational alignment is not perfect, with the center at the > arrow point. > > > But I can't figure out how I can obtain the angle to rotate > > symbols the right way, ie finding the azimuth of the last (or > > first) segment of each line... > > perhaps 'v.to.points dmax=' or v.lrs to set the along-line > node points. unfortunately there is no doffset= option to go > with v.to.point's dmax=, as it would be nice to do like > dmax=100 doffset=50 > to get midpoints of 100m segments (see also the more complicated > v.segment module) > > once 100m line segments are created (sorry no exact recipe for > that comes to mind but it must be possible; maybe together with > the v.to.points nodes?) you can use v.to.db to get azimuth of > the line segments uploaded to the line segment vector's DB, then > use db.execute to attach those to the point vector map, and any > +90 degree rotation if it is needed. > (typically grass uses degrees CCW from the +x axis for rotation) > > > If anyone experienced this, I would be glad to know how you > > proceeded. > > hopefully the above gives you enough to figure something out. > if so, please add the trick to the wiki, or maybe we could > make a script. (ISTR there is something similar for ps.map > there already, it would be good for things like railroad -+--+- > lines) > > even better is if there is a postscript trick for this, then > we could add > > --<-- > --+-- > -->-- > > somehow, like adding a direction=No|yes|tick instruction to > vlines. if so we probably want to add a tick_spacing instruction > too, probably using points as the distance unit for that, > defaulting to something like 8mm. > > > Hamish > _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user