[Proj] Converting between true north, grid north, and magnetic north

[Kurt Schwehr]

Be aware that the magnetic field is time varying.  It can change pretty
quickly near the magnetic poles.

Yet another source... igrf.py

https://earthref.org/PmagPy/cookbook/#x1-1190005.2.54

On Tue, Jan 30, 2018 at 7:03 AM, Charles Karney <charles.karney at sri.com>
wrote:

> GeographicLib https://geographiclib.sourceforge.io provides access to
> several magnetic models via the MagneticField utility.  E.g.,
>
>    echo 42.363 -71.006 | MagneticField -t now
>
> =>
>
>    -14.67 67.08 20228.0 19569.1 -5121.1 47840.0 51940.7
>
> The first number is the current magnetic declination at Boston Logan
> Airport using the wmm2015 magnetic model.
>
> The magnetic models need to be downloaded separately from the
> GeographicLib library using
>
>    geographiclib-get-magnetic
>
> On 01/30/18 06:42, Chen Barnoy wrote:
> > Hi,
> >
> > Is there a way to convert between grid north, true north and magnetic
> > north in Proj4 or another library?
> >
> > Cheers,
> > Chen
> >
> >
> > _______________________________________________
> > Proj mailing list
> > Proj at lists.maptools.org
> > http://lists.maptools.org/mailman/listinfo/proj
> >
> _______________________________________________
> Proj mailing list
> Proj at lists.maptools.org
> http://lists.maptools.org/mailman/listinfo/proj
>



-- 
--
http://schwehr.org
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.maptools.org/pipermail/proj/attachments/20180130/1b6382d7/attachment.htm