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<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=596452116-17092007>Jaap,</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=596452116-17092007></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=596452116-17092007>Have you got your ellipsoids
right?</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=596452116-17092007></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=596452116-17092007>If one of your ellipsoids (commonly the one used
with Plate-Carree) is a sphere, and you ignore that in converting to
geographical latlong (presumably based on WGS84), errors up to nearly 20 km
will occur (latitude dependent). These errors are in the N-S direction, E-W
is usually OK. This effect is beyond projection, latlong/sphere to latlong/WGS84
gives equally long offsets. Try using cs2cs and specify ellipsoids for both
input and output,</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=596452116-17092007></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=596452116-17092007>It is only when one of the ellipsoids is a sphere you
get these large errors, otherwise the error is much smaller.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=596452116-17092007></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=596452116-17092007>See also Frank Warmerdam's answer on June 7th on
gdal-dev: </SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=596452116-17092007><EM>(Re: [Gdal-dev] Does GDAL handle rotated
spheres?)</EM></SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=596452116-17092007></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=596452116-17092007>Best regards,</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=596452116-17092007></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=596452116-17092007>Sjur K :-)</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=596452116-17092007></SPAN></FONT> </DIV><!-- Converted from text/rtf format -->
<P><SPAN lang=no><FONT face=Arial size=2>Sjur Kolberg</FONT></SPAN> <BR><SPAN
lang=no><FONT face=Arial size=2>SINTEF Energy Research</FONT></SPAN> <BR><SPAN
lang=no><FONT face=Arial size=2>N - 7465 Trondheim, Norway</FONT></SPAN>
<BR><SPAN lang=no><FONT face=Arial size=2>Phone +47 - 73 59 72 78</FONT></SPAN>
<BR><SPAN lang=no><FONT face=Arial size=2>Fax +47 - 73 59 72 50</FONT></SPAN>
</P><BR>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left>
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<FONT face=Tahoma size=2><B>From:</B> gdal-dev-bounces@lists.maptools.org
[mailto:gdal-dev-bounces@lists.maptools.org] <B>On Behalf Of
</B>jjknoops@netscape.net<BR><B>Sent:</B> 17. september 2007 15:37<BR><B>To:</B>
gdal-dev@lists.maptools.org<BR><B>Subject:</B> [Gdal-dev] Fwd: plate carree to
latlon projection problem<BR></FONT><BR></DIV>
<DIV></DIV>Hello Everybody,<BR>
<DIV id=AOLMsgPart_3_a2184652-c9ca-41cb-b0c4-451e8cec6560>
<DIV id=AOLMsgPart_3_36eb4dce-a59e-4af0-8c02-9d5e01438a37>
<DIV class=MsoNormal><SPAN><BR>I am using gdal for a couple of year now and I am
very satisfied with it. <BR>But now i have a problem with reprojecting from and
to plate carree(epsg:32662). <BR>I have data in plate carree and I need to
reproject to latlon but i there is an offset between the results and other data
that already in latlon.<BR>I have also used Erdas Imagine 9.1 to do the
reprojecting but i get a different results then from gdal. The results from
Erdas are beter then from gdal<BR><BR>After testing it with a worldwide
dataset<FONT face="Arial, Helvetica, sans-serif">.</FONT> I found that the
offset is almost 0 at (0,0) to several km around Brittian. Is there a problem
with the reprojection using plate carree or do you use a different wgs84 then
Erdas?<BR><BR>I am using gdal from fwtools 1.3.6<BR><BR>Best Regards,<BR>Jaap
Knoops</SPAN><SPAN lang=EN-US></SPAN></DIV><FONT
face="Arial, Helvetica, sans-serif"></FONT>
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