DOUBLE PRECISION FUNCTION FCUL_A (LATITUDE,HEIGHT_M,T_K,ELEV_DEG)
*+
* - - - - - - - - -
* F C U L _ A
* - - - - - - - - -
*
* This function is part of the International Earth Rotation and
* Reference Systems Service (IERS) Conventions software collection.
*
* This function computes the global total FCULa mapping function (Mendes et al. 2002).
* It is dependent on latitude, height, and surface temperature.
*
* 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)
* T_K d Surface temperature given in Kelvin
* ELEV_DEG d Elevation angle given in degrees (See references)
* Returned:
* FCUL_A 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)
* T_K = 300.15D0 Kelvin (August 12, 2009)
* ELEV_DEG = 15D0 degrees (See Mendes et al.)
* expected output: FCUL_A = 3.800243667312344087D0
*
* 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 12 B.E. Stetzler Added header and copyright
* 2009 August 13 B.E. Stetzler Use of DOUBLE PRECISION
* 2009 August 13 B.E. Stetzler Provided test case
* 2009 August 13 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, T_K, T_C
DOUBLE PRECISION COSPHI
DOUBLE PRECISION A10, A11, A12, A13
DOUBLE PRECISION A20, A21, A22, A23
DOUBLE PRECISION A30, A31, A32, A33
PARAMETER ( PI = 3.1415926535897932384626433D0 )
* Preliminary conversions *
* Convert elevation angle to radians
EPSILON = ELEV_DEG * (PI/180D0)
SINE = DSIN(EPSILON)
* Convert temperature to Celsius
T_C = T_K - 273.15D0
COSPHI = DCOS (LATITUDE*(PI/180D0))
* Define coefficients used in the model
A10 = 0.121008D-02
A11 = 0.17295D-05
A12 = 0.3191D-04
A13 = -0.18478D-07
*
A20 = 0.304965D-02
A21 = 0.2346D-05
A22 = -0.1035D-03
A23 = -0.1856D-07
*
A30 = 0.68777D-01
A31 = 0.1972D-04
A32 = -0.3458D-02
A33 = 0.1060D-06
* a, b, and c in Marini continued fraction (Eq. 5)
A1 = A10+A11*T_C+A12*COSPHI+A13*HEIGHT_M
A2 = A20+A21*T_C+A22*COSPHI+A23*HEIGHT_M
A3 = A30+A31*T_C+A32*COSPHI+A33*HEIGHT_M
* numerator in continued fraction
MAP_ZEN = (1.0D0 + A1/(1.0D0 + A2/(1.0D0+A3)))
*
* Results
FCUL_A = MAP_ZEN/(SINE+A1/(SINE+A2/(SINE+A3)))
RETURN
* 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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*
* 5. The Software is provided to the user "as is" and the Center makes
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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
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*
*
*-----------------------------------------------------------------------
END