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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>noel.zinn@hydrometronics.com (email)<BR>http://www.hydrometronics.com
(website)<BR></DIV>
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style='FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline'>
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<DIV> </DIV>
<DIV style="BACKGROUND: #f5f5f5">
<DIV style="font-color: black"><B>From:</B> <A title=cjmce@lsu.edu
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
href="mailto:ndzinn@comcast.net">ndzinn@comcast.net</A> ; <A
title=vanadovv@hetnet.nl href="mailto:vanadovv@hetnet.nl">vanadovv@hetnet.nl</A>
; <A title=proj@lists.maptools.org 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></DIV>
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style='FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline'>
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<DIV>
<DIV>Noel,</DIV>
<DIV> </DIV>
<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>
<DIV>
<DIV id=MAC_OUTLOOK_SIGNATURE>
<DIV>
<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></DIV>
<DIV> </DIV></DIV></DIV></DIV></DIV>
<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
href="mailto:proj-bounces@lists.maptools.org">proj-bounces@lists.maptools.org</A>>
on behalf of "<A
href="mailto:vanadovv@hetnet.nl">vanadovv@hetnet.nl</A>"<BR><SPAN
style="FONT-WEIGHT: bold">Reply-To: </SPAN>"<A
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
href="mailto:ndzinn@comcast.net">ndzinn@comcast.net</A><BR>Datum : 07/07/2016
19:59<BR>Aan : <A
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
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
href="mailto:noel.zinn@hydrometronics.com">noel.zinn@hydrometronics.com</A>
(email) <BR><A
href="http://www.hydrometronics.com">http://www.hydrometronics.com</A>
(website)
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