## stnmap

`stnmap [ -i fname ]`

### Usage Notes

`stnmap` is a GrADS utility that writes out a hash table and/or link list information for station data that allows GrADS to access the report data more efficiently.

If you change the data file - perhaps by appending another time group - you will also have to change the descriptor file to reflect the changes - the new number of times for example - and then rerun the `stnmap` utility.

Note the difference between station descriptor file and a grid descriptor file:

`DTYPE` specify a data type of: station

`STNMAP` gives the file name of the station mapping file.

`XDEF, YDEF, ZDEF` not specified.

`TDEF` describes the time grouping interval and the number of the time groups in the file.

`VAR` surface variables must come first, and are given a zero for the number-of-levels field. Level dependent variables are listed after the surface variables, and are given a one in the number-of-levels field.

### Examples

When a data set, for example `ua.reps` is written, and the descriptor file `stat.ctl`, including the information records for the station data file `ua.reps` is created, you should then create the station map file `ua.map` (named in the `STNMAP` record of the descriptor file; see below) by running the `stnmap` utility.

Example descriptor file: `stat.ctl`

`DSET ^ua.reps
DTYPE station
STNMAP ^ua.map
UNDEF -999.0
TITLE Real Time Upper air obs
TDEF 10 linear 12z18jan1992 12hr
VARS 12
slp 0 99 SLP
ts 0 99 Temps
us 0 99 U Winds
vs 0 99 V Winds
z 1 99 Heightsa
t 1 99 Temps
u 1 99 U Winds
v 1 99 V WInds
ENDVARS`

Running the `stnmap` utility:

  `stnmap -i stat.ctl`

  The station map file `ua.map` is a binary file, which includes the hash table and/or link list information.