[Gdal-dev] geod: azimuth to degrees
jcleary at email.unc.edu
Fri Nov 3 19:58:03 EST 2006
Hey Charlton -
I think you've already got what you need? Geod outputs an azimuth, then
a back azimuth, followed by distance. The two azimuths are different
(i.e. not complimentary like you might expect) because along a great
circle route the azimuth changes throughout. So you're given an initial
azimuth beginning the route to Portland (-66d31'50.141", maybe better
expressed as 360 - 66d31'50.141") and then the initial azimuth to begin
a great circle route from Portland back to Boston (75d39'13.083"). At
least that's what makes sense to me...
I've been using the perl Math::Trig module to do something similar and
it works pretty well so far. Might give geod a try to compare my
results now though...
Charlton Purvis wrote:
> Thanks for getting back to me, Norman. But I don't think that's what I'm
> shopping for.
> The geod command gives me the azimuth in lon,lat followed by a distance. At
> least I think that's right. So for my little arrow that I want to draw, I
> want to have a single degree value from 0 - 360 that is represents the
> azimuth. It's that conversion that I don't know how to do. The scaling
> part is a snap since geod gives that to me on a silver platter.
> Thanks for the help.
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