W3FB12

The W3FB12 routine converts the coordinates of a location on earth given in a
           grid coordinate system overlaid on a Lambert conformal tangent
           cone projection true at a given N or S latitude to the
           natural coordinate system of latitude/longitude.

USAGE:  CALL W3FB12(XI,XJ,ALAT1,ELON1,DX,ELONV,ALATAN,ALAT,ELON,IERR,
                                   IERR)
   Input argument list:
      XI       - I COORDINATE OF THE POINT  REAL*4
      XJ       - J COORDINATE OF THE POINT  REAL*4
      ALAT1    - LATITUDE  OF LOWER LEFT POINT OF GRID (POINT 1,1)
                 LATITUDE <0 FOR SOUTHERN HEMISPHERE; REAL*4
      ELON1    - LONGITUDE OF LOWER LEFT POINT OF GRID (POINT 1,1)
                   EAST LONGITUDE USED THROUGHOUT; REAL*4
      DX       - MESH LENGTH OF GRID IN METERS AT TANGENT LATITUDE
      ELONV    - THE ORIENTATION OF THE GRID.  I.E.,
                 THE EAST LONGITUDE VALUE OF THE VERTICAL MERIDIAN
                 WHICH IS PARALLEL TO THE Y-AXIS (OR COLUMNS OF
                 THE GRID) ALONG WHICH LATITUDE INCREASES AS
                 THE Y-COORDINATE INCREASES.  REAL*4
                 THIS IS ALSO THE MERIDIAN (ON THE OTHER SIDE OF THE
                 TANGENT CONE) ALONG WHICH THE CUT IS MADE TO LAY
                 THE CONE FLAT.
      ALATAN   - THE LATITUDE AT WHICH THE LAMBERT CONE IS TANGENT TO
                 (TOUCHES OR OSCULATES) THE SPHERICAL EARTH.
                  SET NEGATIVE TO INDICATE A
                  SOUTHERN HEMISPHERE PROJECTION; REAL*4
 
   Output argument list:
      ALAT     - LATITUDE IN DEGREES (NEGATIVE IN SOUTHERN HEMI.)
      ELON     - EAST LONGITUDE IN DEGREES, REAL*4
      IERR     - .EQ. 0   IF NO PROBLEM
                 .GE. 1   IF THE REQUESTED XI,XJ POINT IS IN THE
                          FORBIDDEN ZONE, I.E. OFF THE LAMBERT MAP
                          IN THE OPEN SPACE WHERE THE CONE IS CUT.
                 IF IERR.GE.1 THEN ALAT=999. AND ELON=999.
  
REMARKS:
        Formulae and notation loosely based on Hoke, Hayes,
        and Renninger's "Map projections and grid systems...",
        March 1981 AFGWC/TN-79/003

 
W3lib.tar Library contains Fortran 90 decoder/encoder routines for GRIB edition 1. (Fortran90)
Date posted: 2/22/2007