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SUBROUTINE CNVCOORD(IN_LAT,IN_LONG,HEIGHT,ORDER,OUT_LAT,OUT_LONG,
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+ OUT_R,MGFLAG,ERR)
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c
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c $Revision: 1.1 $
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c*****************************************************************
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c Author: Kile B. Baker
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c Johns Hopkins Applied Physics Laboratory
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c*****************************************************************
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c
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c
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c This routine uses a set of coefficients from the file
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c cnvcoord.dat to perform a coordinate
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c conversion between geographic and magnetic (or visa versa)
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c coordinates. The conversion is done using a spherical
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c harmonic expansion.
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c
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c REFERENCE: Baker, K.B. and S. Wing,
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c J. Geophys. Res., Vol. 94, pg. 9139, 1989.
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c
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c**********************************************************************
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c This program and all the associated subroutines and data files
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c may be freely copied and distributed, but the Authors and the
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c Applied Physics Laboratory will not be responsible for the
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c accuracy of the results. Any publication which utilizes results
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c from this software should reference the paper listed above.
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c**********************************************************************
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c
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c This version of the program uses the code written for the
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c Space Forecast Center. The SFC code is modeled after the original
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c PACE magnetic coordinates code.
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c
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c Differences between the original PACE code and the SFC code:
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c The PACE code was based on Corrected Geomagnetic Coordinates
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c for 1980, with the conjugate mapping to the southern hemisphere
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c based on the 1985 IGRF, with time derivatives to model the
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c field at 1988.
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c
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c The PACE code used a spherical expansion of order 4 or less.
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c The new code ignores the "order" parameter in the call to
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c cnvcoord, since the SFC code uses an order of 10 and that is
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c hardcoded.
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c
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c The error codes now include -32 to indicate that the
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c conversion was unsuccessful because the mapping could
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c not be made to the unit sphere. This condition is also
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c indicated by the fact that "out_r" has the value 0.0.
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c
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c The PACE code calculated a value of "out_r". For a successful
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c conversion, the value had to be close to 1.0. The SFC code
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c does not return the value out_r. Therefore, if the conversion
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c was successful, the value of out_r is set to 1.0 exactly. If
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c the conversion was not successful, the value of out_r is set
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c to 0.
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c
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c The PACE code returned non-zero values for out_lat and out_long
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c even if the conversion was not successful (i.e. out_r was not 1.0).
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c The SFC code will return 0.0, 0.0 if the conversion is not
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c successful.
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c
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c ERROR CODES:
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c 0 OK
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c -2 height is invalid (must be between 0 and 2000)
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c -4 mgflag is invalid (must be 1 or 2)
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c -8 in_lat is invalid (must be -90.0 to +90.0)
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c -16 in_long is invalid (must be between -360 and + 360)
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c -32 conversion was invalid (see above)
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c
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cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
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c
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c Log: cnvcoord.f,v
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c Revision 3.2 1996/03/20 22:52:00 baker
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c explicitly declared the size of the integer arguments
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c to the subroutine. This will help avoid trouble when
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c mixing C and Fortran on different machines and different
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c compilers.
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c
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c Revision 3.1 1994/10/14 10:39:49 baker
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c This is the initial version of the wrapper for sfc$$convert_geo_coord.
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c This version also uses the RCS standards to maintain information about the
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c revisions. The previous version of cnvcoord was 2.02. That version
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c is not maintained by RCS.
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C
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C Imported by Bill Rideout on April 21, 2010
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C Modified by nag_apt to convert all reals to double, int16 to ints
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C
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C $Id: cnvcoord.f 3304 2011-01-17 15:25:59Z brideout $
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c
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c
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DOUBLE PRECISION IN_LAT,IN_LONG,HEIGHT,OUT_LAT,OUT_LONG,OUT_R
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INTEGER*4 MGFLAG,ERR,ORDER
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INTEGER*4 I_FLAG,I_ERROR
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c
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c
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c The PACE software accepts in_long values either in the range -180 to
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c +180 or in the range 0 to 360. The SFC software only allows the
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c 0 to 360 range.
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c
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I_FLAG = MGFLAG
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IF (IN_LONG.LT.0.0D0) IN_LONG = IN_LONG + 360.0D0
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CALL CONVERT_GEO_COORD(IN_LAT,IN_LONG,HEIGHT,OUT_LAT,
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+ OUT_LONG,I_FLAG,I_ERROR)
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ERR = I_ERROR
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IF (ERR.EQ.0) THEN
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OUT_R = 1.0D0
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c
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c The SFC code returns longitudes in the range 0 - 360. The
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c PACE code has to return the values in the range -180 to +180.
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c
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IF (OUT_LONG.GT.180.0D0) OUT_LONG = OUT_LONG - 360.0D0
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RETURN
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ELSE IF (ERR.EQ.-32) THEN
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OUT_R = 0.0D0
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RETURN
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ELSE
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RETURN
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END IF
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END
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