Data in rotated grid coordinates

[Ren Diandong]

Hi, Gudrun,

Again, I would like to help out if you can provide the projection code
(i.e., projection roles). Since it seems your projection is not the
usually seen ones (Polar stereographic projections, CSU RAMS oblique
polar stereo projection, NMC high accuracy polar stereo, Mercators,
etc). The best way if provide the way to find (i,j) from (lon, lat).
Then backward coding make the parameter setting for 'pdef'
straightforward and general (no matter where it is, SH, NH, east or west
hemisphere, or even if it spans two special lines such as the
international date line and some inconvenient discontinuity in the grid
counting).

D. Ren
National Weather Center
School of Meteorology
120 David L. Boren Blvd., Suite 5900
Norman, OK. 73072-7307

On Wed, 2006-11-08 at 12:02 +0100, Gudrun Nina Petersen wrote:
> Sorry, I'll try again with a more descriptive subject.
>
> ------
>
> I have data from the UK Met Office Unified Model (UM) that is in rotated
> grid coordinates. My domain is roughly centred on 60N.  North post is brought to
> equator to make equal area grid for the calculations.
> If I plot the data directly,
> the longitude is 18W to 17E and latitude 14S to 32N
>
> However, in reality the data is within the following boundaries
>
>    (75N,120W)-----------------(86N,40W)--------------------(75N,40E)
>        |                          |                             |
>        |                          |                             |
>        |                          |                             |
>        |                          |                             |
>        |                          |                             |
>        |                          |                             |
>        |                          |                             |
>        |                          |                             |
>    (37N,62W)------------------(40N,40W)---------------------(37N,18W)
>
>
> I've read the documentation on PDEF but I still don't understand how to plot
> the data in the correct geographical location.
>
> I can write a pdef-file that contains x(i,j),y(i,j),wrot(i,j), information
> about the correct location of each point: e.g. x(1,1)=-62 and y(1,1,)=37.
>
> However, I can't understand how to use my pdef-file in the ctl-file as the
> data is not on a linear grid anymore when moved to the north.
>
>
> Any help would be greatly appreciated.
>
> Best regards,
>
> G. Nina Petersen
> School of Environmental Sciences
> University of East Anglia
> Norwich
> UK
>