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<DIV dir=ltr><FONT color=#000000 size=2 face="Times New Roman">I got my definition/distinction from Dr. Muneendra Kumar who probably got it from Dr. Ivan I. Mueller.</FONT></DIV>
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<FONT size=2 face=Tahoma><B>From:</B> proj-bounces@lists.maptools.org on behalf of Noel Zinn (cc)<BR><B>Sent:</B> Mon 10-Oct-11 14:21<BR><B>To:</B> PROJ.4 and general Projections Discussions<BR><B>Subject:</B> Re: [Proj] Projection Dev - How to call other projectionsfrom aprojection?<BR></FONT><BR></DIV>
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<P style="MARGIN: 0in 0in 0pt" class=MsoNormal>From the Geodetic Glossary, NGS, NOAA, 1986</P>
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<P style="MARGIN: 0in 0in 0pt" class=MsoNormal>“spheroid </P>
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<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> </SPAN></P>
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<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> </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><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>
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<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>
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<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>
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<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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