Re: [GRASS-user] how to get instantaneous heading of a line at a pt?
On Tue, Feb 17, 2009 at 5:05 AM, Hamish hamis...@yahoo.com wrote: Hi, I have used v.to.points to create a series of points that fall along a line. Now I want to upload to a DB column in the points map the instantaneous heading of the original line at that sample point. This functionality might be added to v.to.db - perhaps using Vect_get_node_line_angle(): http://download.osgeo.org/grass/grass6_progman/level__two_8c.html#a16 Markus ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] how to get instantaneous heading of a line at a pt?
Hamish: I have used v.to.points to create a series of points that fall along a line. Now I want to upload to a DB column in the points map the instantaneous heading of the original line at that sample point. Markus: This functionality might be added to v.to.db - perhaps using Vect_get_node_line_angle(): http://download.osgeo.org/grass/grass6_progman/level__two_8c.html#a16 hmmm. at a node there are two lines, the fn wants to know which one. I have a point somewhere along the line (between two vertices) and want to #1 find the polyline, #2 extract the current linear feature (between two nearest connected vertices), and #3 calc the angle of that line. I see now the corner case of if the point falls exactly on a vertex or a node you will have to average to angles of the lines on either side. I don't think v.to.db could help other than the overall bearing from the polyline's start node to end node. Remember a single line cat can only hold a single value. 'v.distance upload=to_angle' might be something... Hamish ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
[GRASS-user] how to get instantaneous heading of a line at a pt?
Hi, I have used v.to.points to create a series of points that fall along a line. Now I want to upload to a DB column in the points map the instantaneous heading of the original line at that sample point. any ideas? thanks, Hamish ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
