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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>The terms "left-handed" and
"right-handed" are standard in mathematics, but they are ambiguous in
geodesy where they require another convention to clarify their meaning.
That convention would be whether you’re viewing the axis from the
geocenter out, or from the outside in. There is no ambiguity about the "Position
Vector Rotation" and "Coordinate Frame Rotation" terminology.
You’re either rotating the position vector from the geocenter within the
coordinate frame, or rotating the coordinate frame about the position vector.
This terminology originated with UKOOA (UK Offshore Operators’
Association) for (I believe) the P1/90 navigation format in 1990. It was
borrowed by the EPSG, though the Shell geodesist who coined the terms for UKOOA
served (and continues to serve) on the EPSG (now subsumed into the OGP,
International Association of Oil and Gas Producers). Regards, Noel Zinn<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
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face="Times New Roman"><span style='font-size:12.0pt'>
<hr size=2 width="100%" align=center tabindex=-1>
</span></font></div>
<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
proj-bounces@lists.maptools.org [mailto:proj-bounces@lists.maptools.org] <b><span
style='font-weight:bold'>On Behalf Of </span></b>strebe<br>
<b><span style='font-weight:bold'>Sent:</span></b> Friday, April 23, 2010 1:47
PM<br>
<b><span style='font-weight:bold'>To:</span></b> <st1:PersonName w:st="on">PROJ.4
and general Projections Discussions</st1:PersonName><br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [Proj] cs2cs's
+towgs84 usage</span></font><o:p></o:p></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
</div>
<div id=replyPrefaceElement>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>On Apr 23, 2010, at 2:37:28 AM, "Mikael Rittri"
<Mikael.Rittri@carmenta.com> wrote:<o:p></o:p></span></font></p>
</div>
<blockquote style='border:none;border-left:solid blue 1.5pt;padding:0in 0in 0in 4.0pt;
margin-left:3.75pt;margin-top:5.0pt;margin-bottom:5.0pt'>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<pre><font size=2 color=black face="Courier New"><span style='font-size:10.0pt;
color:black'><span style='orphans: 2;widows: 2;-webkit-border-horizontal-spacing: 0px;
-webkit-border-vertical-spacing: 0px;-webkit-text-decorations-in-effect: none;
-webkit-text-size-adjust: auto;-webkit-text-stroke-width: 0px;word-spacing:
0px'>The terms "left-handed" and "right-handed" are<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt;color:black'>just as bad. <o:p></o:p></span></font></pre></blockquote>
</span>
<div>
<p class=MsoNormal><span class=apple-style-span><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>Are they? Those terms are
standard in mathematics, where "Position Vector Transformation" and
"Coordinate Frame Rotation" are unknown. There is no ambiguity in
their meaning or usage.</span></font></span><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>(Not that I would advocate using the terminology in this context, since
EPSG's terminology is Position Vector Transformation versus Coordinate Frame
Rotation. But at least it is not arbitrary like "American" versus
"European".)<o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><span class=apple-style-span><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>Regards,<o:p></o:p></span></font></span></p>
<div>
<p class=MsoNormal><span class=apple-style-span><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>— daan Strebe<o:p></o:p></span></font></span></p>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
</div>
</div>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
</div>
<div id=replyPrefaceElement>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>On Apr 23, 2010, at 2:37:28 AM, "Mikael Rittri"
<Mikael.Rittri@carmenta.com> wrote:<o:p></o:p></span></font></p>
</div>
<blockquote style='border:none;border-left:solid blue 1.5pt;padding:0in 0in 0in 4.0pt;
margin-left:3.75pt;margin-top:5.0pt;margin-bottom:5.0pt'>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<div><span style='orphans: 2;text-align:auto;widows: 2;-webkit-border-horizontal-spacing: 0px;
-webkit-border-vertical-spacing: 0px;-webkit-text-decorations-in-effect: none;
-webkit-text-size-adjust: auto;-webkit-text-stroke-width: 0px;word-spacing:
0px'>
<div style='border:none;border-bottom:solid silver 1.0pt;padding:0in 0in 12.0pt 0in;
margin-bottom:12.0pt' id=felix-mail-header-block>
<table class=MsoNormalTable border=0 cellspacing=1 cellpadding=0 width="100%"
style='width:100.0%'>
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<td valign=top style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=right style='text-align:right'><b><font size=1
color=gray face="Lucida Grande"><span style='font-size:8.0pt;font-family:
"Lucida Grande";color:gray;font-weight:bold'>From:<o:p></o:p></span></font></b></p>
</td>
<td valign=top style='padding:.75pt .75pt .75pt 3.75pt'><span
title=""Mikael Rittri" <Mikael.Rittri@carmenta.com>">
<p class=MsoNormal><font size=1 color=black face="Lucida Grande"><span
style='font-size:8.0pt;font-family:"Lucida Grande";color:black'>"Mikael
Rittri" <Mikael.Rittri@carmenta.com></span><o:p></o:p></span></font></p>
</td>
</tr>
<tr>
<td valign=top style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=right style='text-align:right'><b><font size=1
color=gray face="Lucida Grande"><span style='font-size:8.0pt;font-family:
"Lucida Grande";color:gray;font-weight:bold'>Subject:<o:p></o:p></span></font></b></p>
</td>
<td valign=top style='padding:.75pt .75pt .75pt 3.75pt'>
<p class=MsoNormal><b><font size=1 color=black face="Lucida Grande"><span
style='font-size:8.0pt;font-family:"Lucida Grande";color:black;font-weight:
bold'>Re: [Proj] cs2cs's +towgs84 usage</span></font></b><font size=1
color=black face="Lucida Grande"><span style='font-size:8.0pt;font-family:
"Lucida Grande";color:black'><o:p></o:p></span></font></p>
</td>
</tr>
<tr>
<td valign=top style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=right style='text-align:right'><b><font size=1
color=gray face="Lucida Grande"><span style='font-size:8.0pt;font-family:
"Lucida Grande";color:gray;font-weight:bold'>Date:<o:p></o:p></span></font></b></p>
</td>
<td valign=top style='padding:.75pt .75pt .75pt 3.75pt'>
<p class=MsoNormal><font size=1 color=black face="Lucida Grande"><span
style='font-size:8.0pt;font-family:"Lucida Grande";color:black'>April 23,
2010 2:37:28 AM PDT<o:p></o:p></span></font></p>
</td>
</tr>
<tr>
<td valign=top style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=right style='text-align:right'><b><font size=1
color=gray face="Lucida Grande"><span style='font-size:8.0pt;font-family:
"Lucida Grande";color:gray;font-weight:bold'>To:<o:p></o:p></span></font></b></p>
</td>
<td valign=top style='padding:.75pt .75pt .75pt 3.75pt'><span
title=""PROJ.4 and general Projections Discussions" <proj@lists.maptools.org>">
<p class=MsoNormal><font size=1 color=black face="Lucida Grande"><span
style='font-size:8.0pt;font-family:"Lucida Grande";color:black'>"<st1:PersonName
w:st="on">PROJ.4 and general Projections Discussions</st1:PersonName>"
<proj@lists.maptools.org></span><o:p></o:p></span></font></p>
</td>
</tr>
</table>
</div>
<div id=felix-mail-content-block>
<div><pre style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>About the rotation sign conventions, I would<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>add that calling the two conventions "European"<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>and "American" is not helpful, since there is not<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>much agreement about which convention is which!<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>(Both conventions are used in <st1:place
w:st="on">Europe</st1:place>, and there<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'> is no obvious geographic pattern.) <o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'><o:p> </o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>The terms "left-handed" and "right-handed" are<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>just as bad. <o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'><o:p> </o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>It is better to say that cs2cs uses the sign<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>convention known as the <o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'><o:p> </o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'> Position Vector Transformation.<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'><o:p> </o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>If you look up the +towgs84 parameters on www.epsg-registry.org <o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>(filter by Type: Coordinate Transformation), you will see the text <o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'><o:p> </o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'> "Warning: CARE! Ensure application uses this method! See Guidance Note<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>7-1"<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'><o:p> </o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>above the parameter values. This means that you<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>should scroll down _below_ the parameter values,<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>where you find the Method. If it says:<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'><o:p> </o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'> + Method [Position Vector transformation]<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'><o:p> </o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>you can use the parameters directly in cs2cs.<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>But if it says <o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'><o:p> </o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'> + Method [Coordinate Frame Rotation]<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'><o:p> </o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>you should reverse the signs of the three<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>rotation parameters.<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'><o:p> </o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>Best regards,<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>--<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>Mikael Rittri<o:p></o:p></span></font></pre><pre
style='background:white'><st1:place w:st="on"><st1:City w:st="on"><font size=2
color=black face="Courier New"><span style='font-size:10.0pt;color:black'>Carmenta</span></font></st1:City><font
color=black><span style='color:black'> <st1:State w:st="on">AB</st1:State></span></font></st1:place><font
color=black><span style='color:black'><o:p></o:p></span></font></pre><pre
style='background:white'><st1:country-region w:st="on"><st1:place w:st="on"><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt;
color:black'>SWEDEN</span></font></st1:place></st1:country-region><font
color=black><span style='color:black'><o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>www.carmenta.com<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'><o:p> </o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>-----Original Message-----<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>From: proj-bounces@lists.maptools.org<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>[mailto:proj-bounces@lists.maptools.org] On Behalf Of Frank Warmerdam<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>Sent: den 21 april 2010 18:14<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>To: <st1:PersonName w:st="on">PROJ.4 and general Projections Discussions</st1:PersonName><o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>Subject: Re: [Proj] cs2cs's +towgs84 usage<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'><o:p> </o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>Ilumas wrote:<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>> Dear list,<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>> <o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>> could you kindly confirm that the cs2cs's +towgs84 parameters remain <o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>> the same for a certain datum regardless of the direction of the <o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>> transformation. Some people (e.g.<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>> http://n2.nabble.com/Datum-Shift-WGS84-to-Arc1960-not-working-propberl<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>> y-td3410479.html) <o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>> <http://n2.nabble.com/Datum-Shift-WGS84-to-Arc1960-not-working-propber<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>> ly-td3410479.html>seem to suggest that the values need to be negated <o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>> when going FROM wgs84 TO something else, but this seems a bit strange <o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>> to me. Unfortunately all the examples in the man pages seem to be <o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>> about changing the coordinates TO wgs84...<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'><o:p> </o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>Ilumas,<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'><o:p> </o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>The parameters are always expressed in terms of what it takes to<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>transform to WGS84. If PROJ is transforming from WGS84 it will<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>internally reverse the sense of the transformation.<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'><o:p> </o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>Keep in mind there is also an issue with the handedness of the<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>parameters.<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>Some folks, mostly european, express the parameters with a different<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>handedness. The scripts that generate the "epsg" init file already know<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>about this case and convert to the usual PROJ.4/North American<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>handedness but if you are researching parameters yourself from various<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>sources you may need to be aware of it.<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'><o:p> </o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>Best regards,<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>-- <o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>---------------------------------------+--------------------------------<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>---------------------------------------+------<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>I set the clouds in motion - turn up | Frank Warmerdam,<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>warmerdam@pobox.com<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>light and sound - activate the windows | http://pobox.com/~warmerdam<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>and watch the world go round - Rush | Geospatial Programmer for Rent<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'><o:p> </o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>_______________________________________________<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>Proj mailing list<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>Proj@lists.maptools.org<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>http://lists.maptools.org/mailman/listinfo/proj<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>_______________________________________________<o:p></o:p></span></font></pre><pre
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style='font-size:10.0pt;color:black'>Proj mailing list<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>Proj@lists.maptools.org<o:p></o:p></span></font></pre><pre
style='background:white'><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;color:black'>http://lists.maptools.org/mailman/listinfo/proj<o:p></o:p></span></font></pre></div>
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