<div> <font face="Arial, Helvetica, sans-serif">Hi Frank and Sjur,<br>
<br>
My problem is solved. The method from frank made a good reprojection. It's even better then the erdas reprojection.<br>
The method was: <br>
<i>gdalwarp -s_srs "+proj=eqc +lat_ts=0 +lon_0=0 +x_0=0 +y_0=0 +a=6378137.0 +b=6378137.0 +units=m +towgs84=0,0,0" -t_srs "+proj=longlat +a=6378137.0 +b=6378137.0 +towgs84=0,0,0"</i><br>
</font></div>
<div> <br>
</div>
<div> <font face="Arial, Helvetica, sans-serif">The only strange thing is that this means data projection parameter provided by data supplier is not correct. <br>
<br>
Thank you both for helping me.<br>
<br>
Best regards,<br>
Jaap Knoops<br>
<br>
<br>
<br>
<br>
<br>
</font></div>
-----Original Message-----<br>
From: Frank Warmerdam <warmerdam@pobox.com><br>
To: jjknoops@netscape.net<br>
Cc: gdal-dev@lists.maptools.org<br>
Sent: Tue, 18 Sep 2007 3:14 pm<br>
Subject: Re: [Gdal-dev] Fwd: plate carree to latlon projection problem<br>
<br>
<div id="AOLMsgPart_0_cc989f2b-2cf4-4fc3-845c-64571a68f1c5" style="margin: 0px; font-family: Tahoma,Verdana,Arial,Sans-Serif; font-size: 12px; color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">
<a href="mailto:jjknoops@netscape.net">jjknoops@netscape.net</a> wrote: <br>
> Hi Sjur, <br>
>
> Thanks for your replay. I think you are right when saying it's caused by
> ellipsoid. So I have used this command to reproject <br>
>
> /call gdalwarp -s_srs "+proj=eqc +lat_ts=0 +lon_0=0 +x_0=0 +y_0=0
> +ellps=sphere +a=6378137.0 +es=0.0 +units=m" -t_srs "epsg:4326" <br>
>
> /After comparing this result with previous results then I would say it's
> worse. The offset between the result from gdalwarp and erdas has
> increased. My college has also compared the results with envi and found
> that it's comparable to the erdas results. <br>
<br>
Jaap, <br>
<br>
Try: <br>
<br>
gdalwarp -s_srs "+proj=eqc +lat_ts=0 +lon_0=0 +x_0=0 +y_0=0 <br>
+a=6378137.0 +b=6378137.0 +units=m +towgs84=0,0,0" \ <br>
-t_srs "+a=6378137.0 +b=6378137.0 +towgs84=0,0,0" ... <br>
<br>
This attempts to do a warp from a projection on a spherical ellipsoid <br>
to geographic coordinates on the same ellipsoid. <br>
<br>
Note, using +a and +ellps will conflict and isn't a good idea. And +es <br>
is not recognised by GDAL's proj.4 parser which is not a complete proj.4 <br>
parser. <br>
<br>
Best regards, <br>
--
---------------------------------------+-------------------------------------- <br>
I set the clouds in motion - turn up | Frank Warmerdam, <a href="mailto:warmerdam@pobox.com">warmerdam@pobox.com</a> <br>
light and sound - activate the windows | <a href="http://pobox.com/%7Ewarmerdam" target="_blank">http://pobox.com/~warmerdam</a> <br>
and watch the world go round - Rush | President OSGeo, <a href="http://osgeo.org" target="_blank">http://osgeo.org</a> <br>
<br>
</div>
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