Data

[Ren Diandong]

First, you need to know the GrADS (COARSIAN) convention and the
projection used to create the data. For polar steorographic projection,
for example, you need to know the reference longitude, the reference
latitude, the grid spacing (on the flat map) in x- (W-->E) and y-(N-->S)
directions.
A key parameter is the pole's grid counting in the grid space, which can
be easily figured out if you know the projection rules.

I am not sure of the projection your data is produced with. If you can
provide the projection code, I can write a correspondi
ng code to find the parameters for use pdef (use GrADS to display
preprojected data).

Best wishes,

Diandong


On Wed, 2006-11-08 at 11:59 +0100, Gudrun Nina Petersen wrote:
> 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
>