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<TITLE>gdal_translate with -a_srs option using proj4 syntax and +a=ellipsoid </TITLE>
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<P DIR=LTR><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT FACE="OCR A Extended">Hi all,</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="OCR A Extended">I have a tiff image that has been exported from meteorological software that has know geographic parameters:</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT COLOR="#000000" FACE="Calibri">ELLIPSOID_EQUATOR_RADIUS </FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT COLOR="#000000" FACE="Calibri">6378206.5 </FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><BR>
</SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT COLOR="#000000" FACE="Calibri">ELLIPSOID_POLAR_RADIUS </FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT COLOR="#000000" FACE="Calibri">6356584</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><BR>
</SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT COLOR="#000000" FACE="Calibri">ELLIPSOID_FLATTENING </FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT COLOR="#000000" FACE="Calibri">0.00339</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><BR>
</SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT COLOR="#000000" FACE="Calibri">UPPER_LEFT_X </FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT COLOR="#000000" FACE="Calibri">-3507992.25 </FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><BR>
</SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT COLOR="#000000" FACE="Calibri">UPPER_LEFT_Y </FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT COLOR="#000000" FACE="Calibri">6780696</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><BR>
</SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT COLOR="#000000" FACE="Calibri">LOWER_RIGHT_X </FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT COLOR="#000000" FACE="Calibri">3601343.75 </FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><BR>
</SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT COLOR="#000000" FACE="Calibri">LOWER_RIGHT_Y </FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT COLOR="#000000" FACE="Calibri">2337361</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><BR>
</SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT COLOR="#000000" FACE="Calibri">PROJECTION_TYPE </FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT COLOR="#000000" FACE="Calibri">Mercator</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> </SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><BR>
</SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT COLOR="#000000" FACE="Calibri">CENTER_LONGITUDE_MERCATOR_SPECIFIC </FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT COLOR="#000000" FACE="Calibri">-96 </FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><BR>
</SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT COLOR="#000000" FACE="Calibri">CENTER_LATITUDE </FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT COLOR="#000000" FACE="Calibri">37.910004 </FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><BR>
</SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT COLOR="#000000" FACE="Calibri">CENTER_LONGITUDE </FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT COLOR="#000000" FACE="Calibri">-95.580002 </FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><BR>
</SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT COLOR="#000000" FACE="Calibri">ROTATION </FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT COLOR="#000000" FACE="Calibri">0 </FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><BR>
</SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="OCR A Extended">I am trying to convert this to a geotiff with my eventual goal of converting it to an unprojected tiff.</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><B></B></SPAN><SPAN LANG="en-us"><B><FONT FACE="OCR A Extended">First step is to add the geographic information to the tiff</FONT></B></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT FACE="OCR A Extended">:</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="OCR A Extended">gdal_translate -a_ullr</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT COLOR="#000000" FACE="Calibri">-3507992.25</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT COLOR="#000000" FACE="Calibri"></FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT COLOR="#000000" FACE="Calibri">6780696</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT COLOR="#000000" FACE="Calibri"></FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT COLOR="#000000" FACE="Calibri">3601343.75</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT COLOR="#000000" FACE="Calibri"></FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT COLOR="#000000" FACE="Calibri">2337361</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT FACE="OCR A Extended">-a_srs "+proj=merc +lon_0=96w +a=6378206.5 +f=0.00339" src_image.tiff dest_image.tiff</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="OCR A Extended">The failure I get is:</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="OCR A Extended">Failed to process SRS definition: +proj=merc +lon_0=96w +a=6378206.5 +f=0.00339</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="OCR A Extended">My second attempt was the try the same above command except with a proj string that does not include the +a or +f options</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="OCR A Extended">But instead "+proj=merc +lon_0=96w +datum=WGS84". This did work.</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="OCR A Extended">The problem I am now having is that I bring this image into ArcInfo and for some reason it is shifted north.</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT FACE="OCR A Extended"> I think that being able to correctly apply the ellipsoid equator radius and ellipsoid flattening may fix my problem or a</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT FACE="OCR A Extended">m I missing something?</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><B></B></SPAN><SPAN LANG="en-us"><B><FONT FACE="OCR A Extended">The second step is to create an un</FONT></B></SPAN><SPAN LANG="en-us"><B></B></SPAN><SPAN LANG="en-us"><B><FONT FACE="OCR A Extended">-</FONT></B></SPAN><SPAN LANG="en-us"><B></B></SPAN><SPAN LANG="en-us"><B><FONT FACE="OCR A Extended">projected image from this data</FONT></B></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT FACE="OCR A Extended">:</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT FACE="OCR A Extended"> </FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> </SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT FACE="OCR A Extended">My presumption is the below command will accomplish</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="OCR A Extended">Just that</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT FACE="OCR A Extended">:</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="OCR A Extended">gdalwarp -t_srs '+proj=latlong' -r ${sample_method} ${tmp_image_3} ${final_image</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="OCR A Extended">Any help is fully appreciated.</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="OCR A Extended">Thanks,</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="OCR A Extended">Bill</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"></SPAN></P>
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