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<P class=MsoNormal
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style="FONT-FAMILY: ; COLOR: ; mso-ansi-language: da"><FONT face=Calibri><FONT
style="FONT-SIZE: 11pt" color=#1f497d>6367440 is approximately the average (3
meters off) of the semi-major and semi-minor axes of the WGS84 ellipsoid, which
is of absolutely no significance geodetically.<SPAN
style="mso-spacerun: yes"> </SPAN>It's not the radius of the sphere with
the same volume or the same area as WGS84.<SPAN style="mso-spacerun: yes">
</SPAN>It's just an uniformed guess of an orthographic radius.<SPAN
style="mso-spacerun: yes"> </SPAN>Maybe Blue Marble haven't yet gotten
around to cleaning up Global Mapper's cartography, so I'd hesitate forcing proj4
to match GM.<SPAN style="mso-spacerun: yes"> </SPAN>Anyway, it's time to
use an ellipsoidal orthographic instead, which you can read about
here:</FONT></FONT></SPAN></P>
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style="MARGIN-LEFT: 0in; MARGIN-TOP: 0in; MARGIN-RIGHT: 0in"><SPAN lang=DA
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style="FONT-FAMILY: ; COLOR: ; mso-ansi-language: da"><FONT face=Calibri><FONT
style="FONT-SIZE: 11pt"><A
href="http://www.hydrometronics.com/downloads/Ellipsoidal%20Orthographic%20Projection.pdf">http://www.hydrometronics.com/downloads/Ellipsoidal%20Orthographic%20Projection.pdf</A></FONT></FONT></SPAN></P>
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style="FONT-SIZE: 11pt" color=#1f497d></FONT></FONT></SPAN> </P>
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style="FONT-FAMILY: ; COLOR: ; mso-ansi-language: da"><FONT face=Calibri><FONT
style="FONT-SIZE: 11pt" color=#1f497d>Noel</FONT></FONT></SPAN></P>
<DIV> </DIV>
<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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<DIV style="BACKGROUND: #f5f5f5">
<DIV style="font-color: black"><B>From:</B> <A title=kreve@sdfe.dk
href="mailto:kreve@sdfe.dk">Kristian Evers</A> </DIV>
<DIV><B>Sent:</B> Thursday, July 07, 2016 4:48 AM</DIV>
<DIV><B>To:</B> <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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<P class=MsoNormal><SPAN lang=EN-US
style='FONT-SIZE: 11pt; 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: 11pt; FONT-FAMILY: "Calibri","sans-serif"; COLOR: #1f497d'><o:p></o:p></SPAN> </P>
<P class=MsoNormal><SPAN lang=EN-US
style='FONT-SIZE: 11pt; 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: 11pt; 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: 11pt; FONT-FAMILY: "Calibri","sans-serif"; COLOR: #1f497d'><o:p></o:p></SPAN> </P>
<P class=MsoNormal><SPAN lang=EN-US
style='FONT-SIZE: 11pt; 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: 11pt; FONT-FAMILY: "Calibri","sans-serif"; COLOR: #1f497d'><o:p></o:p></SPAN> </P>
<P class=MsoNormal><SPAN lang=EN-US
style='FONT-SIZE: 11pt; FONT-FAMILY: "Calibri","sans-serif"; COLOR: #1f497d'>Kristian<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN lang=EN-US
style='FONT-SIZE: 11pt; 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: 10pt; FONT-FAMILY: "Tahoma","sans-serif"'>Fra:</SPAN></B><SPAN
style='FONT-SIZE: 10pt; 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></DIV></DIV>
<P class=MsoNormal><o:p></o:p> </P>
<DIV>
<P class=MsoNormal>Does this solve the problem? (taking the radius from the
remotesensing page you referred to):<o:p></o:p></P>
<DIV>
<P class=MsoNormal><o:p></o:p> </P></DIV>
<DIV>
<DIV>
<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></DIV>
<DIV>
<P class=MsoNormal><o:p></o:p> </P></DIV>
<DIV>
<P class=MsoNormal><SPAN
style='FONT-FAMILY: "Courier New"'>Output:</SPAN><o:p></o:p></P></DIV>
<DIV>
<P class=MsoNormal><o:p></o:p> </P></DIV>
<DIV>
<P class=MsoNormal><SPAN
style='FONT-FAMILY: "Courier New"'>-6830.53
11124.18</SPAN><o:p></o:p></P></DIV>
<DIV>
<P class=MsoNormal><o:p></o:p> </P></DIV></DIV>
<DIV>
<P class=MsoNormal>/Thomas<o:p></o:p></P></DIV></DIV></DIV></DIV>
<P>
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