[GRASSLIST:7829] Re: azimuth of a line

[David Finlayson]

The script url was wrong, here is the correct url:

http://students.washington.edu/dfinlays/scripts/2005/cogop.py

David

On 8/8/05, David Finlayson <david.p.finlayson at gmail.com> wrote:
> I'm not sure exactly what you need. But this might help.
> 
> 1) Convert the nodes of your coverage to points using v.to.points
> (format=point option)
> 
> 2) Dump the points as an ascii text stream using v.to.ascii and pipe
> the results into a
> script that calculates the azimuth.
> 
> I have written a small python utility that calculates the distance and
> azimuth along a list of points:
> 
> http://students.washington.edu/dfinlays/scripts/cogop.py
> 
> Here is an example of how it can be used. I have a polygon called
> trimpoly. I convert it to a list of points using v.to.points:
> 
> GRASS 6.1.cvs (UTM10_NAD83): > v.to.points -v input=trimpoly output=trimpolypts
> Building topology ...
> 20 primitives registered
> Building areas:  100%
> 0 areas built
> 0 isles built
> Attaching islands:
> Attaching centroids:  100%
> Topology was built.
> Number of nodes     :   19
> Number of primitives:   20
> Number of points    :   20
> Number of lines     :   0
> Number of boundaries:   0
> Number of centroids :   0
> Number of areas     :   0
> Number of isles     :   0
> 20 points written to output map
> 
> Now I can dump this point file as ascii text:
> 
> > v.out.ascii input=trimpolypts
> 536022.25|5332267.25|-1
> 536029.98|5332292.26|-1
> 536041|5332314.36|-1
> 536066.78|5332355.57|-1
> 536081.01|5332349.24|-1
> 536098.13|5332341.62|-1
> ...
> 
> We can get rid of the pipe characters and replace them with tabs with
> sed and then
> pipe the result to my cogop.py script like this:
> 
> > v.out.ascii input=trimpolypts | sed 's/|/\t/g' | cogop -a
> 0.0  536022.25 5332267.25 -1
> 26.18 17.18 536029.98 5332292.26 -1
> 24.7 26.5 536041 5332314.36 -1
> 48.61 32.03 536066.78 5332355.57 -1
> 15.57 113.98 536081.01 5332349.24 -1
> 18.74 113.99 536098.13 5332341.62 -1
> 
> The first column is the distance between points, the second column is
> the azimuth from point 1 to point 2, finally, the script appends the
> input fields. cogop has a few other options like setting a benchmark
> and calculating cumulative distance, etc. Of course the order of the
> points is important.
> 
> Hope that gives you some ideas,
> 
> David
> 
> 
> On 8/8/05, Carlos Guâno Grohmann <carlos.grohmann at gmail.com> wrote:
> > I was wondering if v.to.db could have a "azimuth" option, to calculate
> > the azimuth of line segments, based on the end vertices coordinates.
> >
> > Carlos
> > --
> > +-----------------------------------------------------------+
> >               Carlos Henrique Grohmann - Guano
> >   Geologist M.Sc  - Doctorate Student at IGc-USP - Brazil
> > Linux User #89721  - carlos dot grohmann at gmail dot com
> > +-----------------------------------------------------------+
> >
> >
> 
> 
> --
> David Finlayson
> Marine Geology & Geophysics
> School of Oceanography
> Box 357940
> University of Washington
> Seattle, WA  98195-7940
> USA
> 
> Office: Marine Sciences Building, Room 112
> Phone: (206) 616-9407
> Web: http://students.washington.edu/dfinlays
> 


-- 
David Finlayson
Marine Geology & Geophysics
School of Oceanography
Box 357940
University of Washington
Seattle, WA  98195-7940
USA

Office: Marine Sciences Building, Room 112
Phone: (206) 616-9407
Web: http://students.washington.edu/dfinlays