DOUBLE PRECISION FUNCTION FCUL_B (LATITUDE,HEIGHT_M,DOY,ELEV_DEG)
*+
* - - - - - - - - -
* F C U L _ B
* - - - - - - - - -
*
* This function is part of the International Earth Rotation and
* Reference Systems Service (IERS) Conventions software collection.
*
* This function computes the global total FCULb mapping function (Mendes et al. 2002).
* There is no dependence on meteorological data for this function.
*
* 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:
* LATITUDE d Latitude given in degrees (North Latitude)
* HEIGHT_M d Height given in meters (mean sea level)
* DOY d Day of the year
* ELEV_DEG d Elevation angle given in degrees (See references)
* Returned:
* FCUL_B d Mapping function to scale total delay (Note 1)
*
* Notes:
*
* 1) These coefficients are based on a LS adjustment of 87766 (cleaned)
* set of traces, based on Ciddor routines to compute refractivity,
* according to IUGG recommendations (1999).
*
* Test case:
* given input: LATITUDE = 30.67166667D0 degrees (McDonald Observatory)
* HEIGHT_M = 2075D0 meters (mean sea level)
* DOY = 224D0 (August 12, 2009)
* ELEV_DEG = 15D0 degrees (See Mendes et al.)
* expected output: FCUL_B = 3.800758725284345996D0
*
* References:
* Mendes, V.B., G. Prates, E.C. Pavlis, D.E. Pavlis,
* and R.B. Langley (2002). "Improved mapping functions for
* atmospheric refraction correction in SLR", Geophysical
* Res. Lett., 29(10), 1414, doi:10.1029/2001GL014394, 2002
*
* Petit, G. and Luzum, B. (eds.), IERS Conventions (2010),
* IERS Technical Note No. 36, BKG (2010)
*
* Revisions:
* 2000 March 31 V.B. Mendes Original code
* 2009 August 13 B.E. Stetzler Added header and copyright
* 2009 August 14 B.E. Stetzler Use of DOUBLE PRECISION
* 2009 August 14 B.E. Stetzler Provided test case
* 2009 August 14 B.E. Stetzler Capitalized all variables for FORTRAN 77
* compatibility and provided more comments
*-----------------------------------------------------------------------
IMPLICIT NONE
DOUBLE PRECISION ELEV_DEG
DOUBLE PRECISION EPSILON
DOUBLE PRECISION PI, SINE
DOUBLE PRECISION A1, A2, A3
DOUBLE PRECISION MAP_ZEN
DOUBLE PRECISION HEIGHT_M, LATITUDE
DOUBLE PRECISION COSPHI , COSDOY, DOY, DOY_C
DOUBLE PRECISION A10, A11, A12, A13, A14
DOUBLE PRECISION A20, A21, A22, A23, A24
DOUBLE PRECISION A30, A31, A32, A33, A34
PARAMETER ( PI = 3.1415926535897932384626433D0 )
* Preliminary conversions *
* Convert elevation angle to radians
EPSILON = ELEV_DEG * (PI/180)
SINE = DSIN(EPSILON)
* Add 182.5 to day of year to account for southern hemisphere
IF (LATITUDE.LT.0.0D0) THEN
DOY_C = DOY + 365.25D0/2.0D0
ELSE
DOY_C = DOY
END IF
COSDOY = DCOS ((DOY_C - 28.0D0) * 2.0D0 * PI / 365.25D0)
COSPHI = DCOS (LATITUDE*(PI/180.0D0))
* Define coefficients used in the model
A10 = 0.116131D-02
A11 = -0.9338D-5
A12 = -0.5958D-8
A13 = -0.24627D-07
A14 = 0.12864D-03
*
A20 = 0.298151D-02
A21 = -0.569D-05
A22 = -0.1655D-07
A23 = -0.2725D-07
A24 = 0.3020D-04
*
A30 = 0.681839D-01
A31 = 0.935D-04
A32 = -0.2394D-06
A33 = 0.304D-07
A34 = -0.2308D-02
* a, b, and c in Marini function
A1 = A10 + A11*COSDOY + A12*LATITUDE**2*COSDOY
. + A13 * HEIGHT_M + A14*COSPHI
A2 = A20 + A21*COSDOY + A22*LATITUDE**2*COSDOY
. + A23 * HEIGHT_M + A24*COSPHI
A3 = A30 + A31*COSDOY + A32*LATITUDE**2*COSDOY
. + A33 * HEIGHT_M + A34*COSPHI
* numerator in continued fraction
MAP_ZEN = (1.0D0 + A1/(1.0D0 + A2/(1.0D0+A3)))
*
* Results
FCUL_B = MAP_ZEN/(SINE+A1/(SINE+A2/(SINE+A3)))
RETURN
* Finished.
*+----------------------------------------------------------------------
*
* Copyright (C) 2008
* IERS Conventions Center
*
* ==================================
* IERS Conventions Software License
* ==================================
*
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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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*
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*
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*
*
*-----------------------------------------------------------------------
END