|
|
SUBROUTINE ALTITUDE_TO_CGM(R_HEIGHT_IN,R_LAT_ALT,R_LAT_ADJ)
|
|
|
c ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
|
|
|
c Original version writen by RADEX, INC. for use on VAX/VMS systems.
|
|
|
c The 1990 version of sfc_convert_geo_coord used a subroutine
|
|
|
c called 'cg_alt_dip'. This subroutine has been replaced
|
|
|
c by two subroutines, cgm_to_altitude, and altitude_to_cgm.
|
|
|
c
|
|
|
c Initial version for POSIX compliant systems made by KBB
|
|
|
c at the Johns Hopkins Univ. Applied Physics Laboratory.
|
|
|
c These revisions have been managed using the Revision Control
|
|
|
c System (RCS). The log of revisions follows:
|
|
|
c
|
|
|
c cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
|
|
|
c
|
|
|
c $Log: not supported by cvs2svn $
|
|
|
c Revision 1.1 1996/03/11 19:23:22 baker
|
|
|
c Initial revision
|
|
|
c
|
|
|
c
|
|
|
c cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
|
|
|
C Purpose:
|
|
|
C
|
|
|
C Computes Latitude Adjustment for R_HEIGHT_IN for use with the
|
|
|
C Spherical Harmonic expansion computation.
|
|
|
C
|
|
|
C Input Arguments:
|
|
|
C
|
|
|
C R_HEIGHT_IN - Single Precision - Input height in km above
|
|
|
C earth mean radius
|
|
|
C
|
|
|
C R_LAT_ALT - Single Precision - R_HEIGHT_IN Corrected Dipole
|
|
|
C Latitude
|
|
|
C
|
|
|
C Output Arguments:
|
|
|
C
|
|
|
C R_LAT_ADJ - Single Precision
|
|
|
C Corrected Geomagnetic Latitude for IFLAG = 1
|
|
|
C Height Adjusted Corrected Dipole Coordinates
|
|
|
C for IFLAG = 2
|
|
|
C
|
|
|
C Local Variables:
|
|
|
C
|
|
|
C RA, R0 - Single Precision - for intermediate results
|
|
|
C
|
|
|
C Constants:
|
|
|
C
|
|
|
C DEGRAD - Double Precision - Conversion Factor
|
|
|
C degrees to radians
|
|
|
C
|
|
|
C ERADIUS - Single Precision - Earth Radius in km
|
|
|
C
|
|
|
C EPS - Single Precision - limit parameter, used to
|
|
|
C avoid computational difficulties
|
|
|
C
|
|
|
C UNIM - Single Precision - limit parameter used to
|
|
|
C avoid computational singularities
|
|
|
C
|
|
|
C Revision History
|
|
|
C
|
|
|
C Written by Radex, Inc., 3 Preston Court, Bedford, MA 01730 12/94
|
|
|
C
|
|
|
C
|
|
|
C .. Parameters ..
|
|
|
DOUBLE PRECISION DEGRAD
|
|
|
PARAMETER (DEGRAD=1.745329251994330D-2)
|
|
|
C ..
|
|
|
C .. Scalar Arguments ..
|
|
|
DOUBLE PRECISION R_HEIGHT_IN,R_LAT_ADJ,R_LAT_ALT
|
|
|
C ..
|
|
|
C .. Local Scalars ..
|
|
|
DOUBLE PRECISION EPS,ERADIUS,R0,RA,UNIM
|
|
|
C ..
|
|
|
C .. Intrinsic Functions ..
|
|
|
INTRINSIC ACOS,COS,SIGN,SQRT
|
|
|
C ..
|
|
|
C .. Save statement ..
|
|
|
SAVE
|
|
|
C ..
|
|
|
C .. Data statements ..
|
|
|
DATA ERADIUS/6371.2D0/
|
|
|
DATA EPS/1.0D-9/
|
|
|
DATA UNIM/0.9999999D0/
|
|
|
C ..
|
|
|
C
|
|
|
C input R_LAT_ALT is an altitude adjusted dipole latitude. The
|
|
|
C following code computes the corresponding 0 km altitude dipole
|
|
|
C latitude (CGM latitude)
|
|
|
C
|
|
|
RA = (COS(DEGRAD*R_LAT_ALT))**2
|
|
|
IF (RA.LT.EPS) RA = EPS
|
|
|
R0 = (1.0D0+R_HEIGHT_IN/ERADIUS)/RA
|
|
|
IF (R0.LT.UNIM) R0 = UNIM
|
|
|
C
|
|
|
R_LAT_ADJ = SIGN(ACOS(SQRT(1.0D0/R0)),R_LAT_ALT)/DEGRAD
|
|
|
C
|
|
|
RETURN
|
|
|
END
|
|
|
|
