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<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">You can use the Mercator projection to digitize true north lines. It is conformal and thus preserves angles. The meridian
convergence is 0 (that is, true north == grid north) all over the map. If you then transform those lines to your chosen CRS you should have a set of lines pointing towards true north instead of grid north.<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">/Kristian<o:p></o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif">Fra:</span></b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif"> Qgis-user [mailto:qgis-user-bounces@lists.osgeo.org]
<b>På vegne af </b>Alexandre Ne</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">to<br>
<b>Sendt:</b> 3. april 2018 11:15<br>
<b>Til:</b> Springfield Harrison <stellargps@gmail.com><br>
<b>Cc:</b> qgis-user <qgis-user@lists.osgeo.org><br>
<b>Emne:</b> Re: [Qgis-user] True North<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Maybe something like this :<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><a href="https://gis.stackexchange.com/q/115531/6191">https://gis.stackexchange.com/q/115531/6191</a><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">Alexandre<o:p></o:p></p>
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<p class="MsoNormal">A ter, 3/04/2018, 10:11, Alexandre Neto <<a href="mailto:senhor.neto@gmail.com">senhor.neto@gmail.com</a>> escreveu:<o:p></o:p></p>
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<p class="MsoNormal">Ah sorry, <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I got lost in translation. You are right, I was talking about the magnetic north, not the geodetic one.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Meanwhile, remembering that all UTM are Transverse Mercator, I don't think there's a CRS that will solve you question.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I think you need to use some formula to convert the grid north measures to true north according to the CRS, and the latitude and longitude of the place. <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Alexandre <o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><o:p> </o:p></p>
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<p class="MsoNormal">A ter, 3/04/2018, 09:25, Springfield Harrison <<a href="mailto:stellargps@gmail.com" target="_blank">stellargps@gmail.com</a>> escreveu:<o:p></o:p></p>
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<p>Alexandre,<o:p></o:p></p>
<p>I believe that true north is actually a constant oriented towards the North Pole, i e 90 degrees north latitude. Also where all meridians converge in the northern hemisphere.<o:p></o:p></p>
<p>The other North orientations are magnetic north and grid North and these do vary as you suggested.<o:p></o:p></p>
<p>I do need to use a UTM projection but need bearings to be in degrees true north.<o:p></o:p></p>
<p>Thanks Alexandre...<o:p></o:p></p>
<p>Cheers . . . . . Spring<o:p></o:p></p>
<p>Samsung Tab 4<o:p></o:p></p>
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<p class="MsoNormal">On Apr 2, 2018 4:27 PM, "Alexandre Neto" <<a href="mailto:senhor.neto@gmail.com" target="_blank">senhor.neto@gmail.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal">AFAIK, true bearing differs in time and location because of magnetic declination. So I don't think there is a such thing as a CRS with true bearings. <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Assuming you are working at regional level, find the magnetic declination for that region and remove it from your observations. Then draw the azimuth using the chosen CRS. I think 26910 will work just fine. <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">If you are at a larger scale, then you may need to use different magnetic declination values for each observation. <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">This may help:<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><a href="https://www.ngdc.noaa.gov/geomag/declination.shtml" target="_blank">https://www.ngdc.noaa.gov/geomag/declination.shtml</a><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Best Regards, <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">Alexandre Neto <o:p></o:p></p>
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<p class="MsoNormal">A seg, 2/04/2018, 23:54, Springfield Harrison <<a href="mailto:stellargps@gmail.com" target="_blank">stellargps@gmail.com</a>> escreveu:<o:p></o:p></p>
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<p class="MsoNormal">Hello,<br>
<br>
I am using CRS 26910, NAD83 / UTM zone 10N, and need to draw lines at<br>
exact true bearings. The Advanced Digitizing Tool seems to do this but<br>
which CRS would I use to ensure that the bearing is True?<br>
<br>
Thanks very much . . .<br>
<br>
<br>
Cheers . . . . . Springfield Harrison<br>
<br>
<br>
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<p class="MsoNormal">-- <o:p></o:p></p>
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<p class="MsoNormal">Alexandre Neto<o:p></o:p></p>
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<p class="MsoNormal">---------------------<o:p></o:p></p>
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<p class="MsoNormal">@AlexNetoGeo<o:p></o:p></p>
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<p class="MsoNormal"><a href="http://sigsemgrilhetas.wordpress.com" target="_blank">http://sigsemgrilhetas.wordpress.com</a><o:p></o:p></p>
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<p class="MsoNormal"><a href="http://gisunchained.wordpress.com" target="_blank">http://gisunchained.wordpress.com</a><o:p></o:p></p>
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<p class="MsoNormal">-- <o:p></o:p></p>
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<p class="MsoNormal">Alexandre Neto<o:p></o:p></p>
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<p class="MsoNormal">---------------------<o:p></o:p></p>
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<p class="MsoNormal">@AlexNetoGeo<o:p></o:p></p>
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<p class="MsoNormal"><a href="http://sigsemgrilhetas.wordpress.com" target="_blank">http://sigsemgrilhetas.wordpress.com</a><o:p></o:p></p>
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<p class="MsoNormal"><a href="http://gisunchained.wordpress.com" target="_blank">http://gisunchained.wordpress.com</a><o:p></o:p></p>
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<p class="MsoNormal">-- <o:p></o:p></p>
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<p class="MsoNormal">Alexandre Neto<o:p></o:p></p>
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<p class="MsoNormal">---------------------<o:p></o:p></p>
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<p class="MsoNormal">@AlexNetoGeo<o:p></o:p></p>
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<p class="MsoNormal"><a href="http://sigsemgrilhetas.wordpress.com">http://sigsemgrilhetas.wordpress.com</a><o:p></o:p></p>
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<p class="MsoNormal"><a href="http://gisunchained.wordpress.com">http://gisunchained.wordpress.com</a><o:p></o:p></p>
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