<div dir="rtl"><div dir="ltr">Thanks!</div><div dir="ltr"><br></div><div dir="ltr">And is there a similar library to convert between grid\UTM north to true north?</div></div><div class="gmail_extra"><div dir="ltr"><br><div class="gmail_quote">2018-01-30 23:59 GMT+02:00 Kurt Schwehr <span dir="ltr">&lt;<a href="mailto:schwehr@gmail.com" target="_blank">schwehr@gmail.com</a>&gt;</span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Be aware that the magnetic field is time varying.  It can change pretty quickly near the magnetic poles.<div><br></div><div>Yet another source... igrf.py</div><div><br></div><div><a href="https://earthref.org/PmagPy/cookbook/#x1-1190005.2.54" target="_blank">https://earthref.org/PmagPy/<wbr>cookbook/#x1-1190005.2.54</a><br></div></blockquote></div><div class="gmail_extra"><div><div class="h5"><br><div class="gmail_quote">On Tue, Jan 30, 2018 at 7:03 AM, Charles Karney <span dir="ltr">&lt;<a href="mailto:charles.karney@sri.com" target="_blank">charles.karney@sri.com</a>&gt;</span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">GeographicLib <a href="https://geographiclib.sourceforge.io" rel="noreferrer" target="_blank">https://geographiclib.sourcefo<wbr>rge.io</a> provides access to<br>
several magnetic models via the MagneticField utility.  E.g.,<br>
<br>
   echo <a href="tel:42.363%20-71.006" value="+14236371006" target="_blank">42.363 -71.006</a> | MagneticField -t now<br>
<br>
=&gt;<br>
<br>
   -14.67 67.08 20228.0 19569.1 -5121.1 47840.0 51940.7<br>
<br>
The first number is the current magnetic declination at Boston Logan<br>
Airport using the wmm2015 magnetic model.<br>
<br>
The magnetic models need to be downloaded separately from the<br>
GeographicLib library using<br>
<br>
   geographiclib-get-magnetic<br>
<div class="m_4937636515122057016HOEnZb"><div class="m_4937636515122057016h5"><br>
On 01/30/18 06:42, Chen Barnoy wrote:<br>
&gt; Hi,<br>
&gt;<br>
&gt; Is there a way to convert between grid north, true north and magnetic<br>
&gt; north in Proj4 or another library?<br>
&gt;<br>
&gt; Cheers,<br>
&gt; Chen<br>
&gt;<br>
&gt;<br>
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</div></div></blockquote></div><br><br clear="all"><div><br></div></div></div><span class="HOEnZb"><font color="#888888">-- <br><div class="m_4937636515122057016gmail_signature" data-smartmail="gmail_signature">--<div><a href="http://schwehr.org" target="_blank">http://schwehr.org</a></div></div>
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