[GEMPAK #KQM-698923]: Gempak - ascii nldn format to gempak

> I have gone through the help pages/tutorials but find that nldn files are 
> problematic due to no stat only slat/slon. I have tried creating a new 
> surface file using sfcfil then adding the data (attached) with both sfstns 
> and sfedit. sfedit doesn't allow changes in slat/slon and sfstns can't seem 
> to recognize format as well as sfedit. I'm sure I am missing something very 
> obvious, could you offer advice.
> 
> How can this be done...
> 
>

Phil,

Your input ASCII data should look like the SFLIST output from a nldn file.
To make things easier and have a "station ID" for NLDN, I use either a "+"
or a "-" character depending on signal polarity (it just makes it convenient to
use SFMAP and plot STID as a parameter to see "+/-" characters on the map
at strike locations.

Here would be the format of a file that contains signal strength and polarity 
in addition to
station lat/lon. If You only have location without any signal, polarity, 
eccentricity etc, you
could encode your time in seconds of the day which I do for the NLDN data since 
the GEMPAK time
only has a granularity of 1 minute:

> more ltng.dat
 PARM = SLAT;SLON;SGNL;MULT                                                     
 

    STN    YYMMDD/HHMM      SLAT     SLON     SGNL     MULT
      +    060210/2230     28.91   -96.31    40.00     1.00
      +    060210/2230     29.16   -96.07    20.00     1.00
      -    060210/2230     30.57   -93.58   -60.00     2.00
      -    060210/2230     29.04   -96.03  -110.00     1.00
      -    060210/2230     30.52   -93.90   -60.00     6.00
      -    060210/2230     28.77   -96.53   -10.00     1.00
      -    060210/2230     30.37   -94.05   -50.00     2.00
      -    060210/2230     31.11   -92.81   -30.00     1.00
      +    060210/2230     31.33   -92.96   360.00     1.00
      +    060210/2230     31.20   -93.28   160.00     1.00
      -    060210/2230     28.91   -96.30   -20.00     1.00
      -    060210/2230     29.27   -96.36   -70.00     1.00
      -    060210/2230     28.96   -96.39  -100.00     3.00
      -    060210/2230     30.47   -94.19  -410.00     3.00
etc...

Now create a ship file ltng.gem such as:
 SFOUTF   = ltng.gem
 SFPRMF   = sgnl;mult
 STNFIL   =  
 SHIPFL   = y
 TIMSTN   = 25000/1
 SFFSRC   =  
 GEMPAK-SFCFIL>r
 
 SFCFIL PARAMETERS: 

 New surface file:      ltng.gem                                                
    
 Parameter file:        sgnl;mult                                               
    
 Station file:                                                                  
    
 Number of stations in STNFIL:       0
 Number of additional stations:      1
 Total number of stations:           1
 Total number of times:          25000

 This file will be a ship file.

Enter <cr> to accept parameters or type EXIT:
 Parameters requested: SFOUTF,SFPRMF,STNFIL,SHIPFL,TIMSTN,SFFSRC.
 GEMPAK-SFCFIL>e


Now you can use SFEDIT such as:
 GEMPAK-SFEDIT>sfefil = ltng.dat
 GEMPAK-SFEDIT>sffile = ltng.gem
 GEMPAK-SFEDIT>r

 SFEDIT PARAMETERS: 

 Edit file:           ltng.dat                                                  
                                                                      
 Output surface file: ltng.gem                                                  
                                                                      

 Parameters to be added to file:

 SLAT SLON SGNL MULT
Enter <cr> to accept parameters or type EXIT:
 Parameters requested: SFEFIL,SFFILE.
 GEMPAK-SFEDIT>e

You now have a surface ship file with the data in GEMPAK format.

Looking at your input file, you need to create a GEMPAK date/time, as
well as look at your longitudes, which lose the negative sign in the
output string when west of 100 degree in your file.

Steve Chiswell
Unidata User Support


Ticket Details
===================
Ticket ID: KQM-698923
Department: Support GEMPAK
Priority: Critical
Status: Closed