[GRASS-user] COGO along a slope
Hamish
hamish_nospam at yahoo.com
Mon Feb 26 23:55:58 EST 2007
Manuel Gimond wrote:
>
> Is there a module (or an easy solution) that will generate line
> features from along-terrain COGO data and a DEM?
> m.cogo will generate [X,Y] values from COGO data, but it assumes that
> the COGO distance measurements have been projected onto a horizontal
> surface. The only work around I can think of requires computing slope
> data (from a DEM for instance) to get at an average cosine of the
> slope underlying each COGO line segment, then correct the COGO
> distance to get its projected counterpart. For instance, an
> along-terrain distance on a 45 degree slope of 100.0 meters should
> translate to a distance of 70.7 meters on a projected plane. This
> correction can be tedious if manually computed by hand (especially
> since multiple iterations may be needed to compute the average slope
> along a line segment). Any ideas?
r.profile, r.transect might help
r.los output map contains vertical angle to target
r.cost?
Maybe v.distance is 3D aware? (I'm not sure). r.distance? (long shot)
Hamish
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