display global data

[Jennifer Adams]

On Feb 23, 2007, at 12:13 AM, Tetsuo Nakazawa wrote:

> Dear everyone,
>
>  My friend asked me the following questions, but I could not answer.
> I hope someone helps me.
>
>  Question:
>   There is a following ctl file. The data is global, starting from
> -179.75 with 0.5 deg resolution.
>   When the display command is issued, then GrADS says that the
> display area is set to like,
>
> LON set to 0 360
> LAT set to ....
> LEV set to ....
> Time ..........
>
>   The question is that the original ctl shows that the western
> boundary of the data is from -179.75,
> however, the display says GrADS changed the longitude, starting from
> 0. Do you know why?
When GrADS detects that a grid 'wraps' the globe, it sets the LON
dimension environment to be 0 to 360. If it doesn't wrap, it sets the
X dimension environment to be 1 to XSIZE. The test for whether a grid
wraps goes like this:
In your descriptor file you have: XDEF n linear v1 v2
temp =  (v1 + (n*v2) - 360)
if (fabs(temp-v1) <  0.01) then the grid wraps.
Non-linear X axes are never tested to see if they wrap.

Jennifer

--
Jennifer M. Adams
IGES/COLA
4041 Powder Mill Road, Suite 302
Calverton, MD 20705
jma at cola.iges.org



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