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<DIV><FONT face=Arial size=2><SPAN
class=562272910-21012008>Hi,</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN
class=562272910-21012008></SPAN></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN class=562272910-21012008>I deal
with climate model data and have regional model data defined on a long/lat
grid with the poles rotated away from their true position (in order to keep the
pole singularities away from the region of interest). Typically this grid
would be defined as follows:</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN
class=562272910-21012008></SPAN></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN
class=562272910-21012008>grid_north_pole_latitude: 39.2 deg (true latitude
of rotated north pole)</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN
class=562272910-21012008>grid_north_pole_longitude: 198.0 deg (true longitude of
rotated north pole)</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN
class=562272910-21012008>north_pole_grid_longitude: 0 deg (longitude of the
prime meridian in the rotated coordinate system)</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN class=562272910-21012008>How would I
represent this coordinate system with proj4 parameters? I have been trying
to use +towgs84:</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN
class=562272910-21012008></SPAN></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN class=562272910-21012008>+proj=longlat
+towgs84=0,0,0,-grid_north_pole_longitude*60*60,90-grid_north_pole_latitude*60*60,north_pole_grid_longitude,0</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN
class=562272910-21012008></SPAN></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN class=562272910-21012008>So far this doesn't
seem to work (I'm using gdal to transform an image to EPSG:4326). Am I on
the right lines? Standard GIS terminology such as datum, spheroid etc. are
unfortunately not part of the standard vocabulary of climate
modellers.</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN
class=562272910-21012008></SPAN></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN class=562272910-21012008>Many
thanks,</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN
class=562272910-21012008>Stephen.</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN
class=562272910-21012008></SPAN></FONT> </DIV>
<DIV align=left><FONT face=Arial size=2>---</FONT></DIV>
<DIV align=left><FONT face=Arial size=2>Stephen Pascoe +44 (0)1235
445980</FONT></DIV>
<DIV align=left><FONT face=Arial size=2>British Atmospheric Data
Centre</FONT></DIV>
<DIV align=left><FONT face=Arial size=2>Rutherford Appleton
Laboratory</FONT></DIV>
<DIV> </DIV></BODY></HTML>