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 |