Hi,Thanks for your replies !
Michael, to answer your question, I don't use only cartesian projections. So it
can be quite difficult to compute the "grid north" for each kind of projection.
Sophia,Are your sure that the Vincenty's algorithm takes care of the projection
when computing the azimuth ? If it is, it is great for me !Thanks,Thomas
Vincenty's algorithm
> Date: Fri, 12 Feb 2010 14:07:39 +1100
> Subject: Re: [Geotools-gt2-users] Compute an azimuth from North Axis
> From: [email protected]
> To: [email protected]; [email protected]
>
> Hi Thomas,
>
> > I am trying to compute an Azimuth between two points with as reference, not
> > the geographic north, but the north of the map projection (in french, this
> > kind of azimuth is called "Gisement" but I didn't find the english word !).
>
> It's commonly called "grid north"
>
> > I can't find how to do that... If somebody can help, it would be great !
>
> If you working with a Cartesian projection (e.g. UTM) and your data
> are uncomplicated (e.g. all location pairs within the same zone) it's
> just a trig calculation. Here's one way to do it...
>
> double atan = Math.atan2(y1 - y0, x1 - x0) * 180.0 / Math.PI;
> double azimuth = (450.0 - atan) % 360;
>
> There's bound to be a method in GeoTools that does this but I haven't
> found it :-)
>
> I'm not sure if I've answered the question that you were asking - if
> not, please get back to us.
>
> Michael
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