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<P style="MARGIN: 0in 0in 0pt" class=MsoNormal>From the Geodetic Glossary, NGS,
NOAA, 1986</P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal> </P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal>“spheroid </P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal> </P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal>(1) Any surface differing but
little from a sphere, (2) An ellipsoid of revolution, (3) A surface derived, by
use of a standard formula for the Earth's potential, by giving the potential one
specific value (Such a surface is intended to be an approximation to the geoid),
(4) By extension, a surface close to the geoid or approximating the geoid.<SPAN
style="mso-spacerun: yes"> </SPAN></P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal> </P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal>Although sense (2) has been
widely used in geodetic literature, modern practice is to employ "ellipsoid of
revolution" as a specific figure, and "spheroid" in sense (1) as a general
term.<SPAN style="mso-spacerun: yes"> </SPAN>Many reference ellipsoids of
older vintage have been called spheroids (e.g., Bessel spheroid) and are so
listed in this glossary.”</P>
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<DIV style="FONT-FAMILY: 'Calibri'; COLOR: #000000; FONT-SIZE: 12pt">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="font-color: black"><B>From:</B> <A title=mfinn@usgs.gov
href="mailto:mfinn@usgs.gov">Michael P Finn</A> </DIV>
<DIV><B>Sent:</B> Monday, October 10, 2011 1:24 PM</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>Cc:</B> <A title=proj@lists.maptools.org
href="mailto:proj@lists.maptools.org">proj@lists.maptools.org</A> ; <A
title=proj-bounces@lists.maptools.org
href="mailto:proj-bounces@lists.maptools.org">proj-bounces@lists.maptools.org</A>
</DIV>
<DIV><B>Subject:</B> Re: [Proj] Projection Dev - How to call other projections
from aprojection?</DIV></DIV></DIV>
<DIV> </DIV></DIV>
<DIV
style="FONT-STYLE: normal; DISPLAY: inline; FONT-FAMILY: 'Calibri'; COLOR: #000000; FONT-SIZE: small; FONT-WEIGHT: normal; TEXT-DECORATION: none"><BR><FONT
size=2 face=sans-serif>Interesting.</FONT> <BR><BR><FONT size=2
face=sans-serif>So where is a threshold (that turns a spheroid into an
ellipsoid)? Technically all spheroids are ellipsoids, mathematically. (Further,
a sphere is also an ellipsoid whose semi-major and semi-minor axes are
identical.)</FONT> <BR><BR><BR><BR><BR>
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<TD><FONT color=#5f5f5f size=1 face=sans-serif>From:</FONT>
<TD><FONT size=1 face=sans-serif>Charles Karney
<charles.karney@sri.com></FONT>
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<TD><FONT color=#5f5f5f size=1 face=sans-serif>To:</FONT>
<TD><FONT size=1 face=sans-serif><proj@lists.maptools.org></FONT>
<TR vAlign=top>
<TD><FONT color=#5f5f5f size=1 face=sans-serif>Date:</FONT>
<TD><FONT size=1 face=sans-serif>10/10/2011 07:34 AM</FONT>
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<TD><FONT color=#5f5f5f size=1 face=sans-serif>Subject:</FONT>
<TD><FONT size=1 face=sans-serif>Re: [Proj] Projection Dev - How to call
other projections from
aprojection?</FONT>
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<TD><FONT color=#5f5f5f size=1 face=sans-serif>Sent by:</FONT>
<TD><FONT size=1
face=sans-serif>proj-bounces@lists.maptools.org</FONT></TD></TR></TBODY></TABLE><BR>
<HR noShade>
<BR><BR><BR><TT><FONT size=2>This may be true is cartography. It's only
partly true in geodesy --<BR>some authors make a distinction,
e.g.,<BR><BR> W. A. Heiskanen and H. Moritz, Physical Geodesy,<BR>
(Freeman, San Fransisco, 1967)<BR><BR>use spheroid to refer to an approximately
spherical shape. (This was,<BR>presumably, its original
meaning.)<BR><BR><BR>On 10/09/11 19:43, Noel Zinn (cc) wrote:<BR>> "Spheroid"
and "ellipsoid" are synonyms for the same thing in geodesy and<BR>>
cartography.<BR>_______________________________________________<BR>Proj mailing
list<BR>Proj@lists.maptools.org<BR></FONT></TT><A
href="http://lists.maptools.org/mailman/listinfo/proj"><TT><FONT
size=2>http://lists.maptools.org/mailman/listinfo/proj</FONT></TT></A><TT><FONT
size=2><BR></FONT></TT><BR><BR>
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