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The original poster stated:<BR>
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<BLOCKQUOTE TYPE=CITE style="BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px"></FONT><FONT COLOR="#000000" BACK="#ffffff" style="BACKGROUND-COLOR: #ffffff" SIZE=2 PTSIZE=10 FAMILY="SANSSERIF" FACE="Arial" LANG="11">take the "radius" of the great/small circle (where 90 degrees is a great circle)</BLOCKQUOTE><BR>
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He doesn't care whether great circles are straight lines. His question is whether he can trust the cartesian circle 90 degrees of arc away from the projection center to be a great circle. The answer is, yes. He can. Also whether other cartesian circles centered on the projection center can be trusted to be small circles. Yes. They can. His procedure works just fine.<BR>
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It does sound like 'geod' is more directly what he wants, though.<BR>
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Regards,<BR>
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daan Strebe<BR>
Geocart author<BR>
http://www.mapthematics.com<BR>
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