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NOTICE: This version of the NSF Unidata web site (archive.unidata.ucar.edu) is no longer being updated.
Current content can be found at unidata.ucar.edu.
To learn about what's going on, see About the Archive Site.
David,
The projection information defines the individual grid point locations, not a
box location.
The data value is the value at the grid point.
If you want the lower left point to be exactly at -2;-2 and the upper right
point to be at 2;2 and a CED projection with .1 degree spacing in the X and Y,
use:
GRID NAVIGATION:
PROJECTION: CED
GRID SIZE: 41 41
LL CORNER: -2.00 -2.00
UR CORNER: 2.00 2.00
Eg, KXKY=41;41. There is one more row and column of data than what you call a
box.
Note that the ability to use the "#" character in KXKY is only for CED grids,
and not
for any other projection, and the number of points is by convention.
Steve Chiswell
Unidata User Support
> Institution: NCAR
> Package Version: 5.9.3
> Operating System: linux 2.6.17-1.2157_FC5smp
> Hardware Information: i686
> Inquiry: Does the longitude (or latitude) of a GEMPAK grid point correspond
> to the edge or to the center of the corresponding grid box?
>
> For example, when I create a GEMPAK grid with GRDAREA=-2;-2;2;2 and
> KXKY=#0.1;0.1, I see the range of longitudes is -2 to 1.9 degrees when I
> print the LONR field with gdlist.
>
> That suggests that the grid point longitude is actually the western edge of
> the grid box, since this would perfectly span the requested range of -2 to 2
> deg.
>
> However, if I assume the grid point longitude is the center of the grid box
> (as usually done in meteorology), the grid spans -2.05 to 1.95 deg. Which is
> correct?
>
>
>
>
Ticket Details
===================
Ticket ID: NZA-884392
Department: Support GEMPAK
Priority: Normal
Status: Closed