SUBROUTINE GDSWIZC9(KGDS,IOPT,NPTS,FILL,XPTS,YPTS,RLON,RLAT,NRET, & LROT,CROT,SROT) C$$$ SUBPROGRAM DOCUMENTATION BLOCK C C SUBPROGRAM: GDSWIZC9 GDS WIZARD FOR ROTATED EQUIDISTANT CYLINDRICAL C PRGMMR: IREDELL ORG: W/NMC23 DATE: 96-04-10 C C ABSTRACT: THIS SUBPROGRAM DECODES THE GRIB GRID DESCRIPTION SECTION C (PASSED IN INTEGER FORM AS DECODED BY SUBPROGRAM W3FI63) C AND RETURNS ONE OF THE FOLLOWING: C (IOPT=+1) EARTH COORDINATES OF SELECTED GRID COORDINATES C (IOPT=-1) GRID COORDINATES OF SELECTED EARTH COORDINATES C FOR STAGGERED ROTATED EQUIDISTANT CYLINDRICAL PROJECTIONS. C (SEE UNDER THE DESCRIPTION OF KGDS TO DETERMINE WHETHER C TO COMPUTE A STAGGERED WIND GRID OR A STAGGERED MASS GRID.) C IF THE SELECTED COORDINATES ARE MORE THAN ONE GRIDPOINT C BEYOND THE THE EDGES OF THE GRID DOMAIN, THEN THE RELEVANT C OUTPUT ELEMENTS ARE SET TO FILL VALUES. C THE ACTUAL NUMBER OF VALID POINTS COMPUTED IS RETURNED TOO. C C PROGRAM HISTORY LOG: C 96-04-10 IREDELL C C USAGE: CALL GDSWIZC9(KGDS,IOPT,NPTS,FILL,XPTS,YPTS,RLON,RLAT,NRET, C & LROT,CROT,SROT) C C INPUT ARGUMENT LIST: C KGDS - INTEGER (200) GDS PARAMETERS AS DECODED BY W3FI63 C IMPORTANT NOTE: IF THE 9TH BIT (FROM RIGHT) OF KGDS(11) C (SCANNING MODE FLAG) IS 1, THEN THIS C THE GRID IS COMPUTED FOR A WIND FIELD; C OTHERWISE IT IS FOR A MASS FIELD. THUS C MOD(KGDS(11)/256,2)=0 FOR MASS GRID. C IOPT - INTEGER OPTION FLAG C (+1 TO COMPUTE EARTH COORDS OF SELECTED GRID COORDS) C (-1 TO COMPUTE GRID COORDS OF SELECTED EARTH COORDS) C NPTS - INTEGER MAXIMUM NUMBER OF COORDINATES C FILL - REAL FILL VALUE TO SET INVALID OUTPUT DATA C (MUST BE IMPOSSIBLE VALUE; SUGGESTED VALUE: -9999.) C XPTS - REAL (NPTS) GRID X POINT COORDINATES IF IOPT>0 C YPTS - REAL (NPTS) GRID Y POINT COORDINATES IF IOPT>0 C RLON - REAL (NPTS) EARTH LONGITUDES IN DEGREES E IF IOPT<0 C (ACCEPTABLE RANGE: -360. TO 360.) C RLAT - REAL (NPTS) EARTH LATITUDES IN DEGREES N IF IOPT<0 C (ACCEPTABLE RANGE: -90. TO 90.) C LROT - INTEGER FLAG TO RETURN VECTOR ROTATIONS IF 1 C C OUTPUT ARGUMENT LIST: C XPTS - REAL (NPTS) GRID X POINT COORDINATES IF IOPT<0 C YPTS - REAL (NPTS) GRID Y POINT COORDINATES IF IOPT<0 C RLON - REAL (NPTS) EARTH LONGITUDES IN DEGREES E IF IOPT>0 C RLAT - REAL (NPTS) EARTH LATITUDES IN DEGREES N IF IOPT>0 C NRET - INTEGER NUMBER OF VALID POINTS COMPUTED C CROT - REAL (NPTS) CLOCKWISE VECTOR ROTATION COSINES IF LROT=1 C SROT - REAL (NPTS) CLOCKWISE VECTOR ROTATION SINES IF LROT=1 C (UGRID=CROT*UEARTH-SROT*VEARTH; C VGRID=SROT*UEARTH+CROT*VEARTH) C C ATTRIBUTES: C LANGUAGE: FORTRAN 77 C C$$$ INTEGER KGDS(200) REAL XPTS(NPTS),YPTS(NPTS),RLON(NPTS),RLAT(NPTS) REAL CROT(NPTS),SROT(NPTS) PARAMETER(RERTH=6.3712E6) PARAMETER(PI=3.14159265358979,DPR=180./PI) C - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - IF(KGDS(1).EQ.201) THEN RLAT1=KGDS(4)*1.E-3 RLON1=KGDS(5)*1.E-3 IROT=MOD(KGDS(6)/8,2) IM=KGDS(7)*2-1 JM=KGDS(8) DLON=KGDS(9)*1.E-3 DLAT=KGDS(10)*1.E-3 KSCAN=MOD(KGDS(11)/256,2) ISCAN=MOD(KGDS(11)/128,2) JSCAN=MOD(KGDS(11)/64,2) NSCAN=MOD(KGDS(11)/32,2) HI=(-1.)**ISCAN HJ=(-1.)**(1-JSCAN) DLONS=HI*DLON DLATS=HJ*DLAT RLONR=-(IM-1)/2*DLONS RLATR=-(JM-1)/2*DLATS SLAT1=SIN(RLAT1/DPR) CLAT1=COS(RLAT1/DPR) SLONR=SIN(RLONR/DPR) CLONR=COS(RLONR/DPR) SLATR=SIN(RLATR/DPR) CLATR=COS(RLATR/DPR) DENOM=1-(CLATR*SLONR)**2 SLAT0=(SLAT1*CLATR*CLONR-SLATR*SQRT(DENOM-SLAT1**2))/DENOM CLAT0=SQRT(1-SLAT0**2) RLON0=RLON1+HI*DPR*ACOS((CLAT0*CLATR*CLONR-SLAT0*SLATR)/CLAT1) C THE FOLLOWING INDENTED LINES ARE A TEMPORARY FIX OF IMPRECISE GRID. C CAUTION: CENTRAL LATITUDE AND LONGITUDE ARE ASSUMED TO BE INTEGERS. SLAT0=SIN(NINT(ASIN(SLAT0)*DPR)/DPR) CLAT0=SQRT(1-SLAT0**2) RLON0=NINT(RLON0) HS=SIGN(1.,MOD(RLON1-RLON0+180+3600,360.)-180) CLON1=COS((RLON1-RLON0)/DPR) SLATR=CLAT0*SLAT1-SLAT0*CLAT1*CLON1 CLATR=SQRT(1-SLATR**2) CLONR=(CLAT0*CLAT1*CLON1+SLAT0*SLAT1)/CLATR RLATR=DPR*ASIN(SLATR) RLONR=HS*DPR*ACOS(CLONR) DLATS=RLATR/(-(JM-1)/2) DLONS=RLONR/(-(IM-1)/2) IF(KSCAN.EQ.0) THEN IS1=(JM+1)/2 ELSE IS1=JM/2 ENDIF XMIN=0 XMAX=IM+1 IF(IM.EQ.NINT(360/ABS(DLONS))) XMAX=IM+2 YMIN=0 YMAX=JM+1 NRET=0 C - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - C TRANSLATE GRID COORDINATES TO EARTH COORDINATES IF(IOPT.EQ.0.OR.IOPT.EQ.1) THEN DO N=1,NPTS XPTF=YPTS(N)+(XPTS(N)-IS1) YPTF=YPTS(N)-(XPTS(N)-IS1)+KSCAN IF(XPTF.GE.XMIN.AND.XPTF.LE.XMAX.AND. & YPTF.GE.YMIN.AND.YPTF.LE.YMAX) THEN HS=HI*SIGN(1.,XPTF-(IM+1)/2) RLONR=(XPTF-(IM+1)/2)*DLONS RLATR=(YPTF-(JM+1)/2)*DLATS CLONR=COS(RLONR/DPR) SLATR=SIN(RLATR/DPR) CLATR=COS(RLATR/DPR) SLAT=CLAT0*SLATR+SLAT0*CLATR*CLONR IF(SLAT.LE.-1) THEN CLAT=0. CLON=COS(RLON0/DPR) RLON(N)=0 RLAT(N)=-90 ELSEIF(SLAT.GE.1) THEN CLAT=0. CLON=COS(RLON0/DPR) RLON(N)=0 RLAT(N)=90 ELSE CLAT=SQRT(1-SLAT**2) CLON=(CLAT0*CLATR*CLONR-SLAT0*SLATR)/CLAT CLON=MIN(MAX(CLON,-1.),1.) RLON(N)=MOD(RLON0+HS*DPR*ACOS(CLON)+3600,360.) RLAT(N)=DPR*ASIN(SLAT) ENDIF NRET=NRET+1 IF(LROT.EQ.1) THEN IF(IROT.EQ.1) THEN IF(CLATR.LE.0) THEN CROT(N)=-SIGN(1.,SLATR*SLAT0) SROT(N)=0 ELSE SLON=SIN((RLON(N)-RLON0)/DPR) CROT(N)=(CLAT0*CLAT+SLAT0*SLAT*CLON)/CLATR SROT(N)=SLAT0*SLON/CLATR ENDIF ELSE CROT(N)=1 SROT(N)=0 ENDIF ENDIF ELSE RLON(N)=FILL RLAT(N)=FILL ENDIF ENDDO C - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - C TRANSLATE EARTH COORDINATES TO GRID COORDINATES ELSEIF(IOPT.EQ.-1) THEN DO N=1,NPTS IF(ABS(RLON(N)).LE.360.AND.ABS(RLAT(N)).LE.90) THEN HS=SIGN(1.,MOD(RLON(N)-RLON0+180+3600,360.)-180) CLON=COS((RLON(N)-RLON0)/DPR) SLAT=SIN(RLAT(N)/DPR) CLAT=COS(RLAT(N)/DPR) SLATR=CLAT0*SLAT-SLAT0*CLAT*CLON IF(SLATR.LE.-1) THEN CLATR=0. RLONR=0 RLATR=-90 ELSEIF(SLATR.GE.1) THEN CLATR=0. RLONR=0 RLATR=90 ELSE CLATR=SQRT(1-SLATR**2) CLONR=(CLAT0*CLAT*CLON+SLAT0*SLAT)/CLATR CLONR=MIN(MAX(CLONR,-1.),1.) RLONR=HS*DPR*ACOS(CLONR) RLATR=DPR*ASIN(SLATR) ENDIF XPTF=(IM+1)/2+RLONR/DLONS YPTF=(JM+1)/2+RLATR/DLATS IF(XPTF.GE.XMIN.AND.XPTF.LE.XMAX.AND. & YPTF.GE.YMIN.AND.YPTF.LE.YMAX) THEN XPTS(N)=IS1+(XPTF-(YPTF-KSCAN))/2 YPTS(N)=(XPTF+(YPTF-KSCAN))/2 NRET=NRET+1 IF(LROT.EQ.1) THEN IF(IROT.EQ.1) THEN IF(CLATR.LE.0) THEN CROT(N)=-SIGN(1.,SLATR*SLAT0) SROT(N)=0 ELSE SLON=SIN((RLON(N)-RLON0)/DPR) CROT(N)=(CLAT0*CLAT+SLAT0*SLAT*CLON)/CLATR SROT(N)=SLAT0*SLON/CLATR ENDIF ELSE CROT(N)=1 SROT(N)=0 ENDIF ENDIF ELSE XPTS(N)=FILL YPTS(N)=FILL ENDIF ELSE XPTS(N)=FILL YPTS(N)=FILL ENDIF ENDDO ENDIF C - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - C PROJECTION UNRECOGNIZED ELSE IRET=-1 IF(IOPT.GE.0) THEN DO N=1,NPTS RLON(N)=FILL RLAT(N)=FILL ENDDO ENDIF IF(IOPT.LE.0) THEN DO N=1,NPTS XPTS(N)=FILL YPTS(N)=FILL ENDDO ENDIF ENDIF C - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - END