GDRADR creates a gridded 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
    GDPFUN    Scalar grid or vector grid function
    GDFILE    Grid file
    RADTIM    Radar composite current/dattim
    RADDUR    Radar time window (minutes prior to RADTIM)
    RADFRQ    Update Frequency
    CPYFIL    Grid file whose navigation is to be used in new grid file | subare
    STNFIL    Station information file
    MAXGRD    Maximum number of grids
    RADMODE   Radar operational mode
    NDVAL     Replacement value for "ND" (default RMISSD)
 
 

PROGRAM DESCRIPTION
 
   GDRADR samples NEXRAD Level III (NIDS) products to a common
   grid projection.

   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
   the output file does not already exist, and CPYFIL is blank.

   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.

   GDPFUN is a list of data parameters for which composites are created.
   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 GDPFUN 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, GDRADR 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.


EXAMPLES
 
    1.  Create a 4km National composite of NEXRAD base reflectivity (N0Q)
        and echo tops (NET). 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 grid output file using the YYYYMMDD_radar.gem file name
        template. Accept data only from radars operating in precipitation
        mode.

        PROJ     = lcc/25;-103;60
        GRDAREA  = 23.0;-120.0;47.0;-65.0
        KXKY     = 720;500
        GDPFUN   = n0q ! net
        GDFILE   = YYYYMMDD_radr.gem
        RADTIM   = current
        RADDUR   = 30
        RADFRQ   = 5
        CPYFIL   =
        STNFIL   = nexrad.tbl
        MAXGRD   = 1000
	RADMODE  = P

    2.  Create a radar mosaic using grid #218 for the total precipitation
        nexrad product (NTP). Use the default radar station table.
        Use a 15 minute time window ending at to 010302/1200.

        PROJ     =
        GRDAREA  =
        KXKY     =
        GDPFUN   = ntp
        GDFILE   = YYYYMMDD_ntp.gem
        RADTIM   = 010302/1200
        RADDUR   = 15
        RADFRQ   =
        CPYFIL   = #218
        STNFIL   =
        MAXGRD   = 500
	RADMODE  =

ERROR MESSAGES
 
    [GDRADR  +5]   Mode rejected: ...
    [GDRADR  +4]    Write grid ...
    [GDRADR  +3]    Using default station file ...
    [GDRADR  +2]    NEXRIII template not found using ...
    [GDRADR  +1]    Too old: ...
    [GDRADR  0]    Using:   ...
    [GDRADR  -1]    Fatal error initializing TAE.
    [GDRADR  -2]    Fatal error reading TAE parameters.
    [GDRADR  -3]    Fatal error initializing GEMPLT.
    [GDRADR  -4]    Failed to read grid projection ...
    [GDRADR  -5]    Could not create grid file ...
    [GDRADR  -6]    Could not open grid file ...
    [GDRADR  -7]    Warning: navigation block does not match file
    [GDRADR  -8]    Station table ... not found