POLATES3

The POLATES3 routine performs budget interpolation
             from any grid to any grid for scalar fields.
             It requires a grid for the output fields (KGDSO(1)>=0).
             The algorithm simply computes (weighted) averages
             of bilinearly interpolated points arranged in a square box
             centered around each output grid point and stretching
             nearly halfway to each of the neighboring grid points.
             Options allow choices of number of points in each radius
             from the center point (IPOPT(1)) which defaults to 2
             (If IPOPT(1)=-1) meaning that 25 points will be averaged;
             Further options are the respective weights for the radius
             points starting at the center point (IPOPT(2:2+IPOPT(1))
             which defaults to all 1 (If IPOPT(1)=-1 or IPOPT(2)=-1).
             A special interpolation is done if IPOPT(2)=-2.
             In this case, the boxes stretch nearly all the way to
             each of the neighboring grid points and the weights
             are the adjoint of the bilinear interpolation weights.
             This case gives quasi-second-order budget interpolation.
             another option is the minimum percentage for mask,
             i.e. percent valid input data required to make output data,
             (IPOPT(3+IPOPT(1)) which defaults to 50 (if -1).
             only horizontal interpolation is performed.
             The grids are defined by their grid description sections
             (passed in integer form as decoded by subprogram w3fi63).

             The current code recognizes the following projections:
                (KGDS(1)=000) EQUIDISTANT CYLINDRICAL
                (KGDS(1)=001) MERCATOR CYLINDRICAL
                (KGDS(1)=003) LAMBERT CONFORMAL CONICAL
                (KGDS(1)=004) GAUSSIAN CYLINDRICAL (SPECTRAL NATIVE)
                (KGDS(1)=005) POLAR STEREOGRAPHIC AZIMUTHAL
                (KGDS(1)=202) ROTATED EQUIDISTANT CYLINDRICAL (ETA NATIVE)

             Where KGDS could be either input KGDSI or output KGDSO.
             As an added bonus the number of output grid points
             and their latitudes and longitudes are also returned.
             On the other hand, the output can be a set of station points
             If KGDSO(1)<0, in which case the number of points
             and their latitudes and longitudes must be input.
             Input bitmaps will be interpolated to output bitmaps.
             Output bitmaps will also be created when the output grid
             extends outside of the domain of the input grid.
             The output field is set to 0 where the output bitmap is off.

USAGE:    CALL POLATES3(IPOPT,KGDSI,KGDSO,MI,MO,KM,IBI,LI,GI,
                        NO,RLAT,RLON,IBO,LO,GO,IRET)

   Input argument list:
      IPOPT    - INTEGER (20) INTERPOLATION OPTIONS
                 IPOPT(1) IS NUMBER OF RADIUS POINTS
                 (DEFAULTS TO 2 IF IPOPT(1)=-1);
                 IPOPT(2:2+IPOPT(1)) ARE RESPECTIVE WEIGHTS
                 (DEFAULTS TO ALL 1 IF IPOPT(1)=-1 OR IPOPT(2)=-1).
                 IPOPT(3+IPOPT(1)) IS MINIMUM PERCENTAGE FOR MASK
                 (DEFAULTS TO 50 IF IPOPT(3+IPOPT(1)=-1)
      KGDSI    - INTEGER (200) INPUT GDS PARAMETERS AS DECODED BY W3FI63
      KGDSO    - INTEGER (200) OUTPUT GDS PARAMETERS
      MI       - INTEGER SKIP NUMBER BETWEEN INPUT GRID FIELDS IF KM>1
                 OR DIMENSION OF INPUT GRID FIELDS IF KM=1
      MO       - INTEGER SKIP NUMBER BETWEEN OUTPUT GRID FIELDS IF KM>1
                 OR DIMENSION OF OUTPUT GRID FIELDS IF KM=1
      KM       - INTEGER NUMBER OF FIELDS TO INTERPOLATE
      IBI      - INTEGER (KM) INPUT BITMAP FLAGS
      LI       - LOGICAL*1 (MI,KM) INPUT BITMAPS (IF SOME IBI(K)=1)
      GI       - REAL (MI,KM) INPUT FIELDS TO INTERPOLATE
 
  Output argument list:
      NO       - INTEGER NUMBER OF OUTPUT POINTS
      RLAT     - REAL (MO) OUTPUT LATITUDES IN DEGREES
      RLON     - REAL (MO) OUTPUT LONGITUDES IN DEGREES
      IBO      - INTEGER (KM) OUTPUT BITMAP FLAGS
      LO       - LOGICAL*1 (MO,KM) OUTPUT BITMAPS (ALWAYS OUTPUT)
      GO       - REAL (MO,KM) OUTPUT FIELDS INTERPOLATED
      IRET     - INTEGER RETURN CODE
                 0    SUCCESSFUL INTERPOLATION
                 2    UNRECOGNIZED INPUT GRID OR NO GRID OVERLAP
                 3    UNRECOGNIZED OUTPUT GRID
                 31   INVALID UNDEFINED OUTPUT GRID
                 32   INVALID BUDGET METHOD PARAMETERS
 
 
iplib.tar Library contains subroutines to be used for interpolating almost any grids used at NCEP. (Fortran90)
Date posted: 2/22/2007