w3fb03.f

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C> @file
C> @brief Convert i,j grid coordinates to lat/lon.
C> @author Ralph Jones @date 1986-07-17
 
C> Converts i,j grid coordinates to the corresponding
C> latitude/longitude on a southern hemisphere polar stereographic
C> map projection.
C>
C> Program history log.
C> - Ralph Jones 1986-07-17 Convert to fortran 77.
C> - Ralph Jones 1990-08-31 Convert to cray cft77 fortran.
C>
C> @param[in] XI Real i coordinate.
C> @param[in] XJ Real j coordinate.
C> @param[in] XMESHL Real grid interval in km.
C> @param[out] TLAT Real s.h. latitude.
C> @param[out] TLONG Real longitude.
C>
C> @author Ralph Jones @date 1986-07-17
      SUBROUTINE w3fb03(XI, XJ, XMESHL, TLAT, TLONG)
C
C     ...GIVEN ... XI/XJ GRID COORDINATES OF A POINT RELATIVE
C     ...        TO (0,0) AT SOUTH POLE
C     ...TO COMPUTE TLAT,TLONG ON THE SRN HEMI POLAR STEREO PROJECTION
C     ...WITH 80W VERTICAL AT TOP OF THE MAP
C
       DATA  degprd/57.2957795/
       DATA  earthr/6371.2/
C
      re  = (earthr * 1.86603) / xmeshl
      gi2 = re * re
C
C     ...WHERE GI2 IS THE SQUARE OF DISTANCE IN GRID INTERVALS
C     ...   FROM POLE TO EQUATOR...
C
      r2 = xi * xi + xj * xj
      IF (r2 .NE. 0.0) THEN
C
      xlong = degprd * atan2(xj,xi)
      tlong = xlong - 10.0
      IF (tlong .LT. 0.0) tlong = tlong + 360.0
      tlat  = asin((gi2 - r2)/(gi2 + r2)) * degprd
      tlat  = -tlat
C
      ELSE
      tlat = -90.0
C
C     ...FOR SOUTH POLE...
C
      tlong = 0.0
      ENDIF
C
      RETURN
      END