SUBROUTINE VMF1 (AH,AW,DMJD,DLAT,ZD,VMF1H,VMF1W)
*+
* - - - - - - - - -
* V M F 1
* - - - - - - - - -
*
* This routine is part of the International Earth Rotation and
* Reference Systems Service (IERS) Conventions software collection.
*
* This subroutine determines the Vienna Mapping Function 1 (VMF1).
* This is the site dependent version.
*
* In general, Class 1, 2, and 3 models represent physical effects that
* act on geodetic parameters while canonical models provide lower-level
* representations or basic computations that are used by Class 1, 2, or
* 3 models.
*
* Status: Class 1 model
*
* Class 1 models are those recommended to be used a priori in the
* reduction of raw space geodetic data in order to determine
* geodetic parameter estimates.
* Class 2 models are those that eliminate an observational
* singularity and are purely conventional in nature.
* Class 3 models are those that are not required as either Class
* 1 or 2.
* Canonical models are accepted as is and cannot be classified as a
* Class 1, 2, or 3 model.
*
* Given:
* AH d Hydrostatic coefficient a (Note 1)
* AW d Wet coefficient a (Note 1)
* DMJD d Modified Julian Date
* DLAT d Latitude given in radians (North Latitude)
* ZD d Zenith distance in radians
*
* Returned:
* VMF1H d Hydrostatic mapping function (Note 2)
* VMF1W d Wet mapping function (Note 2)
*
* Notes:
*
* 1) The coefficients can be obtained from the website
* http://ggosatm.hg.tuwien.ac.at/DELAY/SITE/
*
* 2) The mapping functions are dimensionless scale factors.
*
* Test case:
* given input: AH = 0.00127683D0
* AW = 0.00060955D0
* DMJD = 55055D0
* DLAT = 0.6708665767D0 radians (NRAO, Green Bank, WV)
* ZD = 1.278564131D0 radians
*
* expected output: VMF1H = 3.424342122738070593D0
* VMF1W = 3.448299714692572238D0
*
* References:
*
* Boehm, J., Werl, B., and Schuh, H., (2006),
* "Troposhere mapping functions for GPS and very long baseline
* interferometry from European Centre for Medium-Range Weather
* Forecasts operational analysis data," J. Geophy. Res., Vol. 111,
* B02406, doi:10.1029/2005JB003629
*
* Please mind that the coefficients in this paper are wrong.
* The corrected version of the paper can be found at:
* http://ggosatm.hg.tuwien.ac.at/DOCS/PAPERS/2006Boehm_etal_VMF1.pdf
*
* Petit, G. and Luzum, B. (eds.), IERS Conventions (2010),
* IERS Technical Note No. 36, BKG (2010)
*
* Revisions:
* 2005 October 02 J. Boehm Original code
* 2009 August 17 B.E. Stetzler Added header and copyright
* 2009 August 17 B.E. Stetzler More modifications and defined twopi
* 2009 August 17 B.E. Stetzler Provided test case
* 2009 August 17 B.E. Stetzler Capitalized all variables for FORTRAN 77
* compatibility
* 2010 September 08 B.E. Stetzler Provided new primary website to obtain
* VMF coefficients
* 2011 July 21 J. Boehm Changed latitude to ellipsoidal latitude
* 2012 January 11 B.E. Stetzler Updated website in notes, removed reference
* to old website, and added note in references
* 2012 January 12 B.E. Stetzler Corrected test case input and output
* mentioned in the header
*-----------------------------------------------------------------------
IMPLICIT NONE
DOUBLE PRECISION AH, AW, DMJD, DLAT, ZD, VMF1H, VMF1W
DOUBLE PRECISION DOY, BH, C0H, C11H, C10H, PHH, CH, SINE, BETA,
. GAMMA, TOPCON, BW, CW, PI, TWOPI
PARAMETER ( PI = 3.1415926535897932384626433D0 )
PARAMETER (TWOPI = 6.283185307179586476925287D0)
*+---------------------------------------------------------------------
* Reference day is 28 January 1980
* This is taken from Niell (1996) to be consistent
*----------------------------------------------------------------------
DOY = DMJD - 44239D0 + 1 - 28
BH = 0.0029D0;
C0H = 0.062D0
IF (DLAT.LT.0D0) THEN ! southern hemisphere
PHH = PI
C11H = 0.007D0
C10H = 0.002D0
ELSE ! northern hemisphere
PHH = 0D0
C11H = 0.005D0
C10H = 0.001D0
END IF
CH = C0H + ((DCOS(DOY/365.25D0*TWOPI + PHH)+1D0)*C11H/2D0
. + C10H)*(1D0-DCOS(DLAT))
SINE = DSIN(PI/2D0 - ZD)
BETA = BH/( SINE + CH )
GAMMA = AH/( SINE + BETA)
TOPCON = (1D0 + AH/(1D0 + BH/(1D0 + CH)))
VMF1H = TOPCON/(SINE+GAMMA)
BW = 0.00146D0
CW = 0.04391D0
BETA = BW/( SINE + CW )
GAMMA = AW/( SINE + BETA)
TOPCON = (1D0 + AW/(1D0 + BW/(1D0 + CW)))
VMF1W = TOPCON/(SINE+GAMMA)
* Finished.
*+----------------------------------------------------------------------
*
* Copyright (C) 2008
* IERS Conventions Center
*
* ==================================
* IERS Conventions Software License
* ==================================
*
* NOTICE TO USER:
*
* BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING TERMS AND CONDITIONS
* WHICH APPLY TO ITS USE.
*
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*
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*
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*
* c) The name(s) of all modified routine(s) that you distribute
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*
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*
* Correspondence concerning IERS Conventions software should be
* addressed as follows:
*
* Gerard Petit
* Internet email: gpetit[at]bipm.org
* Postal address: IERS Conventions Center
* Time, frequency and gravimetry section, BIPM
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*
* or
*
* Brian Luzum
* Internet email: brian.luzum[at]usno.navy.mil
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*
*
*-----------------------------------------------------------------------
END