<font color='black' size='3' face='Georgia, Times New Roman, Times, Serif'><font size="3">The typos, yes. Unfortunate. Even more unfortunate is the fictitious integral given for the length of a geodesic. This was repeated by Fenna in <i>A Compendium of Map Projections</i>. Now we’ll never be rid of it.<br>
<br>
— daan<br>
Mapthematics LLC<br>
<br>
</font>
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<div style="font-family:helvetica,arial;font-size:10pt;color:black">-----Original Message-----<br>
From: Noel Zinn (cc) <ndzinn@comcast.net><br>
To: PROJ.4 and general Projections Discussions <proj@lists.maptools.org><br>
Sent: Thu, Jul 7, 2016 1:24 pm<br>
Subject: [Proj] Difference in Orthographic projection between Proj4 and Global Mapper<br>
<br>
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<div style="FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline">Frederick
Pearson, II?<span style="mso-spacerun: yes"> </span>I didn't know that,
Cliff, but, after going down the rat holes of innumerable typos in his book "Map
Projections: Theory and Applications", I sort of gave up on Pearson.<span style="mso-spacerun: yes"> </span>CRC Press didn't serve him well.<span style="mso-spacerun: yes"> -Noel</span></div>
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<div style="FONT-SIZE: 12pt; FONT-FAMILY: 'Calibri'; COLOR: #000000">Noel Zinn,
Principal, Hydrometronics LLC<br>
+1-832-539-1472 (office), +1-281-221-0051
(cell)<br>
<a href="mailto:noel.zinn@hydrometronics.com">noel.zinn@hydrometronics.com</a> (email)<br>
<a href="http://www.hydrometronics.com" target="_blank">http://www.hydrometronics.com</a>
(website)<br>
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<div style="font-color: black"><b>From:</b> <a title="cjmce@lsu.edu" target="_blank" href="mailto:cjmce@lsu.edu">Clifford J Mugnier</a> </div>
<div><b>Sent:</b> Thursday, July 07, 2016 2:28 PM</div>
<div><b>To:</b> <a title="ndzinn@comcast.net" target="_blank" href="mailto:ndzinn@comcast.net">ndzinn@comcast.net</a> ; <a title="vanadovv@hetnet.nl" target="_blank" href="mailto:vanadovv@hetnet.nl">vanadovv@hetnet.nl</a>
; <a title="proj@lists.maptools.org" target="_blank" href="mailto:proj@lists.maptools.org">PROJ.4
and general Projections Discussions</a> </div>
<div><b>Subject:</b> Re: [Proj] Difference in Orthographic projection between
Proj4 and Global Mapper</div>
</div>
</div>
<div> </div>
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<div>Noel,</div>
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<div>Which then begs the question, why not use the Authalic Latitude function
for your spherical equal area projection …</div>
<div> </div>
<div>That’s what Pearson tried to do when proposed the idea for the old Bonne
projection applications in reproducing 19th century graticules.</div>
<div>Not mathematically equivalent, but that’s what he proposed.</div>
<div> </div>
<div>Cliff </div>
<div> </div>
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<div style="FONT-SIZE: 12px; FONT-FAMILY: times"><font face="Copperplate">Clifford
J. Mugnier, CP,CMS,FASPRS</font></div>
<div style="FONT-SIZE: 12px; FONT-FAMILY: times"><font face="Copperplate">Chief of
Geodesy,</font></div>
<div style="FONT-SIZE: 12px; FONT-FAMILY: times"><font face="Copperplate">Center
for GeoInformatics (C4G)</font></div>
<div style="FONT-SIZE: 12px; FONT-FAMILY: times"><font face="Copperplate">266 ERAD
(Research)</font></div>
<div style="FONT-SIZE: 12px; FONT-FAMILY: times"><font face="Copperplate">3335
PFT (Academic)</font></div>
<div style="FONT-SIZE: 12px; FONT-FAMILY: times"><font face="Copperplate">Dept. of
Civil & Environmental Engineering</font></div>
<div style="FONT-SIZE: 12px; FONT-FAMILY: times"><font face="Copperplate">LOUISIANA STATE UNIVERSITY</font></div>
<div style="FONT-SIZE: 12px; FONT-FAMILY: times"><font face="Copperplate">Baton
Rouge, LA 70803</font></div>
<div style="FONT-SIZE: 12px; FONT-FAMILY: times"><font face="Copperplate">Research 225-578-4578</font></div>
<div style="FONT-SIZE: 12px; FONT-FAMILY: times"><font face="Copperplate">Academic 225-578-8536</font></div>
<div style="FONT-SIZE: 12px; FONT-FAMILY: times"><font face="Copperplate">Cell
225-328-8975</font></div>
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<div> </div>
<span id="OLK_SRC_BODY_SECTION">
<div style="FONT-SIZE: 12pt; BORDER-TOP: #b5c4df 1pt solid; FONT-FAMILY: calibri; BORDER-RIGHT: medium none; BORDER-BOTTOM: medium none; COLOR: black; PADDING-BOTTOM: 0in; TEXT-ALIGN: left; PADDING-TOP: 3pt; PADDING-LEFT: 0in; BORDER-LEFT: medium none; PADDING-RIGHT: 0in"><span style="FONT-WEIGHT: bold">From: </span><<a target="_blank" href="mailto:proj-bounces@lists.maptools.org">proj-bounces@lists.maptools.org</a>>
on behalf of "<a target="_blank" href="mailto:vanadovv@hetnet.nl">vanadovv@hetnet.nl</a>"<br>
<span style="FONT-WEIGHT: bold">Reply-To: </span>"<a target="_blank" href="mailto:vanadovv@hetnet.nl">vanadovv@hetnet.nl</a>", "PROJ.4 and general
Projections Discussions"<br>
<span style="FONT-WEIGHT: bold">Date:
</span>Thursday, July 7, 2016 at 2:22 PM<br>
<span style="FONT-WEIGHT: bold">To:
</span>"PROJ.4 and general Projections Discussions"<br>
<span style="FONT-WEIGHT: bold">Subject: </span>Re: [Proj] Difference in Orthographic
projection between Proj4 and Global Mapper<br>
</div>
<div> </div>
<div>
<div>
<div>The radius of 6370997 is the integer part of the authalic radius of the
Clarke 1866 ellipsoid.</div>
<div>The calculated value would be around 6370997.24063266 m.</div>
<div> </div>
<div> </div>
<div> </div>
<div>Greetings,</div>
<div> </div>
<div>Oscar van Vlijmen</div>
<div><br>
</div>
<blockquote style="MARGIN-LEFT: 15px; MARGIN-RIGHT: 0px">----Origineel
Bericht----<br>
Van : <a target="_blank" href="mailto:ndzinn@comcast.net">ndzinn@comcast.net</a><br>
Datum : 07/07/2016
19:59<br>
Aan : <a target="_blank" href="mailto:proj@lists.maptools.org">proj@lists.maptools.org</a><br>
Onderwerp
: Re: [Proj] Difference in Orthographic projection between Proj4 and Global
Mapper<br>
<br>
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<div style="FONT-SIZE: 12pt; FONT-FAMILY: calibri; COLOR: rgb(0,0,0)">
<div>Hi Huw, </div>
<div></div>
<div>Given ellipsoidal parameters there are many spherical radii from which to
choose. Wikipedia gives a good summary: </div>
<div></div>
<div><a title="https://en.wikipedia.org/wiki/Earth_radius" target="_blank" href="https://en.wikipedia.org/wiki/Earth_radius">https://en.wikipedia.org/wiki/Earth_radius</a></div>
<div></div>
<div>But where does GCTP’s 6370997 come from? It’s close to some radii
for WGS84, but no cigar. Is it just a convention? Anyone know?
</div>
<div></div>
<div>Of course, if you’re mapping on a sphere “closeness” shouldn’t really
matter very much. Consistency should matter more, and, in that sense, a
conventional radius would be useful. </div>
<div></div>
<div>Noel </div>
<div></div>
<div style="FONT-SIZE: 12pt; FONT-FAMILY: calibri; COLOR: rgb(0,0,0)">Noel
Zinn, Principal, Hydrometronics LLC <br>
+1-832-539-1472 (office),
+1-281-221-0051 (cell) <br>
<a target="_blank" href="mailto:noel.zinn@hydrometronics.com">noel.zinn@hydrometronics.com</a>
(email) <br>
<a target="_blank" href="http://www.hydrometronics.com">http://www.hydrometronics.com</a>
(website)
<br>
</div>
</div>
</div>
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</blockquote><br>
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