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<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">No, it is the same as using +ellps=sphere – as was already tried. By doing a bit of manual bisection on the radius I came up with the following
that more or less matches the results from GM:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">> echo -3.1 52.1 | proj +proj=ortho +lat_0=52 +lon_0=-3 +a=6367440 +units=m +no_defs<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">-6826.72 11117.97<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I have no idea if that works for other coordinates though! Probably not…
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Kristian<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">Fra:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> proj-bounces@lists.maptools.org [mailto:proj-bounces@lists.maptools.org]
<b>På vegne af </b>Thomas Knudsen<br>
<b>Sendt:</b> 7. juli 2016 11:32<br>
<b>Til:</b> PROJ.4 and general Projections Discussions<br>
<b>Emne:</b> Re: [Proj] Difference in Orthographic projection between Proj4 and Global Mapper<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Does this solve the problem? (taking the radius from the remotesensing page you referred to):<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">$ echo -3.1 52.1 | proj +proj=ortho +lat_0=52 +lon_0=-3 +x_0=0 +y_0=0 +a=6370997 +f=0 +units=m +no_defs</span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">Output:</span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">-6830.53 11124.18</span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">/Thomas<o:p></o:p></p>
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