[GEMPAK #VPZ-489654]: GEMPAK - SFGRAM Coordinate Question

> Goal: Clickable interactive state (WA) map that uses GEMPAK to produce 
> meteograms from MM5 model output. Clicks do NOT necesarily land on 
> predetermined stations.
> 
> Question: I have been messing with SFGRAM to produce a meteogram without 
> using STATION but rather lat/lon coordinates. Is there a easy/recommended way 
> to do this?
> 
> Ideas: We already produce the MM5.gem files so could I trick GEMPAK by 
> creating a new station (using SFSTNS to change station info locally as not to 
> disrupt the department wide GEMPAK) with the user click as the lat/lon, name 
> the station TEST, then plot the data from the MM5.gem file using SFGRAM 
> STATION=test. This seems a little 'clunky'... do you have any other 
> suggestions?
> 
> I have searched through the logs/e-mail threads with no luck and wonder if 
> you can give advice.
> 
> Thanks,
> 
> Phil
> 


Phil,

The SFGRAM program requires the surface observations to be at a station 
location, so you
either have to:
1) interpolate your data to the user clicked location
or
2) determine the "nearest" station for which you have data with respect to the 
clicked location

If you are going to do the first option above, you can interpolate the grid 
data to a surface locations
using GDGSFC, where you would create the surface file with your "TEST" id or 
some
predetermined STNM. This could all be done though a script and existing GEMPAK 
programs since
you can obtain the "CURSOR GPOINT" selected lat;lon value from the GEMPAK 
display
program, generate the surface file and plot with SFGRAM in a short time.
The down side here is if you have a lot of user clicks, that may be inefficient 
depending on
the number of user clicks you would have.

The second option would follow the closest predetermined location (this is like
the clickable NWX map, or the nearest station readout in NMAP2). My assumption 
here would
be that it may be advantageous to create a bogus grid of station locations (eg 
an ID
every .01 degree in lat and lon within a model domain as an example) and then 
use the closest station 
if that would be sufficient for your use. I put together a short program 
(calling sequence for $CGEMLIB/clo 
routines is clo_init, clo_tclosest, clo_tgid) that will return the "closest" 
station ID for a 
supplied lat;lon (eg "cursor gpoint") if you would like to see that. The 
advantage here would be 
if you had a lot of clicks as the interpolation would only be done once in 
GDGSFC.

Steve Chiswell
Unidata User Support

Ticket Details
===================
Ticket ID: VPZ-489654
Department: Support GEMPAK
Priority: High
Status: Closed