NEXRCOMP creates a GINI format image composite of NEXRAD level III products.

INPUT PARAMETERS
 
    GRDAREA   Area covered by grid
    PROJ      Map projection/angles/margins|drop flag
    KXKY      Number of grid points in x;y
    CPYFIL    Grid file whose navigation is to be used in new grid file | subare
    GFUNC     Scalar grid
    RADTIM    Radar composite current/dattim
    RADDUR    Radar time window (minutes prior to RADTIM)
    RADFRQ    Update Frequency
    STNFIL    Station information file
    RADMODE   Radar operational mode
    SATFIL    Radar image filename(s)
    GDFILE    Grid file
    NDVAL     Replacement value for "ND" (default RMISSD)
    MAXGRD    Maximum number of grids
    COMPRESS  Write output in compressed format
 
 

PROGRAM DESCRIPTION
 
   NEXRCOMP samples NEXRAD Level III (NIDS) products to a common
   grid projection. Then creates a GINI format image with
   appropriate header information using the grid as the
   image raster, before saving the grid to a GEMPAK grid file.
   NEXRCOMP is not limited by the traditional LLMXGD
   limitation for grid files.

   NEXRCOMP uses a suplemental table $GEMTBL/unidata/nex2gini.tbl to specify 
   configurations for product identifiers so that the generated images
   are correctly identified for enhancement tables in $GEMTBL/sat/imgtyp.tbl.

   SATFIL specifies the output GIF file. If the file already exists,
   it is overwritten.

   GDFILE specifies the output grid file. If the file does not already
   exist, the file is created using the grid defined by CPYFIL,
   or if CPYFIL is not defined then by PROJ, GRDAREA, and KXKY.

   CPYFIL may provide either an existing grid file to read the projection
   information from, or a grid number (#nnn) defined in grdnav.tbl.

   PROJ, GRDAREA, and KXKY define a grid navigation as in GDCFIL if
   CPYFIL is blank. The GINI format has additional restrictions
   which limit which GEMPAK projections may be used. These are,
   LCC tangent projection (eg la1 and la2 are the same), STR, and CED.

   STNFIL is the station table which supplies radar IDs to be searched
   for the composite. If STNFIL is blank, then 'nexrad.tbl' is used
   by default.

   GFUNC is the data parameter which the composite is created for.
   The NEXRAD file naming is assumed to be such that the site identifier
   and the product type are both present in the directory/file naming
   structure. The datatype.tbl template NEXRIII is used to provide the
   file naming convention used. If NEXRIII is not found in the template
   database, a default directory structure for NEXRAD data is assumed
   where the root directory $RAD/NIDS contains a tree structure supporting
   %SITE%/%PROD%/%PROD%_YYYYMMDD_HHNN file names. The %SITE% template
   will be replaced by the site IDs in the STNFIL table. The %PROD% will
   be replaced by the GFUNC product name. The GEMPAK data/time template
   will be used with RADTIM and RADDUR to determine which NEXRAD products
   are in the valid time range.

   RADTIM determined the output grid time for the radar composite.
   The value of RADTIM may either be 'current', or a GEMPAK dattim.
   If 'current' is selected for RADTIM, then the current system clock
   time is used. No data files later than RADTIM will be included
   in the composite. RADDUR provides the time window previous to
   RADTIM in order to include data for each site. The time closest
   to RADTIM will be used. A default RADDUR of 30 minutes is
   used if RADDUR is blank.

   RADFRQ is the frequency in minutes at which the program will run.
   When RADFRQ is defined, NEXRCOMP will wait for the specified time
   before rerunning. This option is most useful when RADTIM is
   set to 'current'. When the program is sleeping, ctrl-c can be
   used to exit the loop and return to the dynamic tutor. If
   RADFRQ is not set, the dynamic tutor will be re-entered at the
   end of processing the radar mosaic.

   RADMODE allows the user to select whether to include radar data
   from sites operating in (P) precipitation/storm mode, (C) clear
   air mode, and/or (M) maintainence mode. The default, if none
   are specified is data from all 3 modes (PCM). Multiple modes
   may be specified.

   COMPRESS allows the user to optionally write the GINI file using PNG
   compression for the image raster. The GINI header will identify the
   image as a compressed product.


EXAMPLES
 
    1.  Create a 1km National composite of NEXRAD base reflectivity (N0Q).
        Use the current time with a 30 minute window for data. Rerun the
        mosaic creation continuously with a 5 minute wait period between
        each update. Use the nexrad.tbl station table. Create the 
        output file using the rad_YYYYMMDD_HHNN file name template.
        Accept data from radars operating in precipitation and
        clear air mode. 

        GRDAREA  = 23;-120;47.2634;-63.5664
        PROJ     = lcc/40;-100;40
        KXKY     = 4736;3000
        CPYFIL   =
        GFUNC    = n0q
        RADTIM   = current
        RADDUR   = 30
        RADFRQ   = 5
        STNFIL   = nexrad.tbl
        RADMODE  = PC
        SATFIL   = rad_YYYYMMDD_HHNN
        GDFILE   = YYYYMMDD_radr.gem
	MAXGRD   = 1000

ERROR MESSAGES
 
    [NEXRCOMP  +5] Mode rejected: ...
    [NEXRCOMP  +4]  Write image ...
    [NEXRCOMP  +3]  Using default station file ...
    [NEXRCOMP  +2]  NEXRIII template not found using ...
    [NEXRCOMP  +1]  Too old: ...
    [NEXRCOMP  0]  Using:   ...
    [NEXRCOMP  -1]  Fatal error initializing TAE.
    [NEXRCOMP  -2]  Fatal error reading TAE parameters.
    [NEXRCOMP  -3]  Fatal error initializing GEMPLT.
    [NEXRCOMP  -4]  Failed to read grid projection ...
    [NEXRCOMP  -8]  Station table ... not found