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Diffstat (limited to 'ast/erfa/refco.c')
| -rw-r--r-- | ast/erfa/refco.c | 262 |
1 files changed, 0 insertions, 262 deletions
diff --git a/ast/erfa/refco.c b/ast/erfa/refco.c deleted file mode 100644 index 918d990..0000000 --- a/ast/erfa/refco.c +++ /dev/null @@ -1,262 +0,0 @@ -#include "erfa.h" - -void eraRefco(double phpa, double tc, double rh, double wl, - double *refa, double *refb) -/* -** - - - - - - - - - -** e r a R e f c o -** - - - - - - - - - -** -** Determine the constants A and B in the atmospheric refraction model -** dZ = A tan Z + B tan^3 Z. -** -** Z is the "observed" zenith distance (i.e. affected by refraction) -** and dZ is what to add to Z to give the "topocentric" (i.e. in vacuo) -** zenith distance. -** -** Given: -** phpa double pressure at the observer (hPa = millibar) -** tc double ambient temperature at the observer (deg C) -** rh double relative humidity at the observer (range 0-1) -** wl double wavelength (micrometers) -** -** Returned: -** refa double* tan Z coefficient (radians) -** refb double* tan^3 Z coefficient (radians) -** -** Notes: -** -** 1) The model balances speed and accuracy to give good results in -** applications where performance at low altitudes is not paramount. -** Performance is maintained across a range of conditions, and -** applies to both optical/IR and radio. -** -** 2) The model omits the effects of (i) height above sea level (apart -** from the reduced pressure itself), (ii) latitude (i.e. the -** flattening of the Earth), (iii) variations in tropospheric lapse -** rate and (iv) dispersive effects in the radio. -** -** The model was tested using the following range of conditions: -** -** lapse rates 0.0055, 0.0065, 0.0075 deg/meter -** latitudes 0, 25, 50, 75 degrees -** heights 0, 2500, 5000 meters ASL -** pressures mean for height -10% to +5% in steps of 5% -** temperatures -10 deg to +20 deg with respect to 280 deg at SL -** relative humidity 0, 0.5, 1 -** wavelengths 0.4, 0.6, ... 2 micron, + radio -** zenith distances 15, 45, 75 degrees -** -** The accuracy with respect to raytracing through a model -** atmosphere was as follows: -** -** worst RMS -** -** optical/IR 62 mas 8 mas -** radio 319 mas 49 mas -** -** For this particular set of conditions: -** -** lapse rate 0.0065 K/meter -** latitude 50 degrees -** sea level -** pressure 1005 mb -** temperature 280.15 K -** humidity 80% -** wavelength 5740 Angstroms -** -** the results were as follows: -** -** ZD raytrace eraRefco Saastamoinen -** -** 10 10.27 10.27 10.27 -** 20 21.19 21.20 21.19 -** 30 33.61 33.61 33.60 -** 40 48.82 48.83 48.81 -** 45 58.16 58.18 58.16 -** 50 69.28 69.30 69.27 -** 55 82.97 82.99 82.95 -** 60 100.51 100.54 100.50 -** 65 124.23 124.26 124.20 -** 70 158.63 158.68 158.61 -** 72 177.32 177.37 177.31 -** 74 200.35 200.38 200.32 -** 76 229.45 229.43 229.42 -** 78 267.44 267.29 267.41 -** 80 319.13 318.55 319.10 -** -** deg arcsec arcsec arcsec -** -** The values for Saastamoinen's formula (which includes terms -** up to tan^5) are taken from Hohenkerk and Sinclair (1985). -** -** 3) A wl value in the range 0-100 selects the optical/IR case and is -** wavelength in micrometers. Any value outside this range selects -** the radio case. -** -** 4) Outlandish input parameters are silently limited to -** mathematically safe values. Zero pressure is permissible, and -** causes zeroes to be returned. -** -** 5) The algorithm draws on several sources, as follows: -** -** a) The formula for the saturation vapour pressure of water as -** a function of temperature and temperature is taken from -** Equations (A4.5-A4.7) of Gill (1982). -** -** b) The formula for the water vapour pressure, given the -** saturation pressure and the relative humidity, is from -** Crane (1976), Equation (2.5.5). -** -** c) The refractivity of air is a function of temperature, -** total pressure, water-vapour pressure and, in the case -** of optical/IR, wavelength. The formulae for the two cases are -** developed from Hohenkerk & Sinclair (1985) and Rueger (2002). -** -** d) The formula for beta, the ratio of the scale height of the -** atmosphere to the geocentric distance of the observer, is -** an adaption of Equation (9) from Stone (1996). The -** adaptations, arrived at empirically, consist of (i) a small -** adjustment to the coefficient and (ii) a humidity term for the -** radio case only. -** -** e) The formulae for the refraction constants as a function of -** n-1 and beta are from Green (1987), Equation (4.31). -** -** References: -** -** Crane, R.K., Meeks, M.L. (ed), "Refraction Effects in the Neutral -** Atmosphere", Methods of Experimental Physics: Astrophysics 12B, -** Academic Press, 1976. -** -** Gill, Adrian E., "Atmosphere-Ocean Dynamics", Academic Press, -** 1982. -** -** Green, R.M., "Spherical Astronomy", Cambridge University Press, -** 1987. -** -** Hohenkerk, C.Y., & Sinclair, A.T., NAO Technical Note No. 63, -** 1985. -** -** Rueger, J.M., "Refractive Index Formulae for Electronic Distance -** Measurement with Radio and Millimetre Waves", in Unisurv Report -** S-68, School of Surveying and Spatial Information Systems, -** University of New South Wales, Sydney, Australia, 2002. -** -** Stone, Ronald C., P.A.S.P. 108, 1051-1058, 1996. -** -** Copyright (C) 2013-2016, NumFOCUS Foundation. -** Derived, with permission, from the SOFA library. See notes at end of file. -*/ -{ - int optic; - double p, t, r, w, ps, pw, tk, wlsq, gamma, beta; - - -/* Decide whether optical/IR or radio case: switch at 100 microns. */ - optic = ( wl <= 100.0 ); - -/* Restrict parameters to safe values. */ - t = ERFA_GMAX ( tc, -150.0 ); - t = ERFA_GMIN ( t, 200.0 ); - p = ERFA_GMAX ( phpa, 0.0 ); - p = ERFA_GMIN ( p, 10000.0 ); - r = ERFA_GMAX ( rh, 0.0 ); - r = ERFA_GMIN ( r, 1.0 ); - w = ERFA_GMAX ( wl, 0.1 ); - w = ERFA_GMIN ( w, 1e6 ); - -/* Water vapour pressure at the observer. */ - if ( p > 0.0 ) { - ps = pow ( 10.0, ( 0.7859 + 0.03477*t ) / - ( 1.0 + 0.00412*t ) ) * - ( 1.0 + p * ( 4.5e-6 + 6e-10*t*t ) ); - pw = r * ps / ( 1.0 - (1.0-r)*ps/p ); - } else { - pw = 0.0; - } - -/* Refractive index minus 1 at the observer. */ - tk = t + 273.15; - if ( optic ) { - wlsq = w * w; - gamma = ( ( 77.53484e-6 + - ( 4.39108e-7 + 3.666e-9/wlsq ) / wlsq ) * p - - 11.2684e-6*pw ) / tk; - } else { - gamma = ( 77.6890e-6*p - ( 6.3938e-6 - 0.375463/tk ) * pw ) / tk; - } - -/* Formula for beta from Stone, with empirical adjustments. */ - beta = 4.4474e-6 * tk; - if ( ! optic ) beta -= 0.0074 * pw * beta; - -/* Refraction constants from Green. */ - *refa = gamma * ( 1.0 - beta ); - *refb = - gamma * ( beta - gamma / 2.0 ); - -/* Finished. */ - -} -/*---------------------------------------------------------------------- -** -** -** Copyright (C) 2013-2016, NumFOCUS Foundation. -** All rights reserved. -** -** This library is derived, with permission, from the International -** Astronomical Union's "Standards of Fundamental Astronomy" library, -** available from http://www.iausofa.org. -** -** The ERFA version is intended to retain identical functionality to -** the SOFA library, but made distinct through different function and -** file names, as set out in the SOFA license conditions. The SOFA -** original has a role as a reference standard for the IAU and IERS, -** and consequently redistribution is permitted only in its unaltered -** state. The ERFA version is not subject to this restriction and -** therefore can be included in distributions which do not support the -** concept of "read only" software. -** -** Although the intent is to replicate the SOFA API (other than -** replacement of prefix names) and results (with the exception of -** bugs; any that are discovered will be fixed), SOFA is not -** responsible for any errors found in this version of the library. -** -** If you wish to acknowledge the SOFA heritage, please acknowledge -** that you are using a library derived from SOFA, rather than SOFA -** itself. -** -** -** TERMS AND CONDITIONS -** -** Redistribution and use in source and binary forms, with or without -** modification, are permitted provided that the following conditions -** are met: -** -** 1 Redistributions of source code must retain the above copyright -** notice, this list of conditions and the following disclaimer. -** -** 2 Redistributions in binary form must reproduce the above copyright -** notice, this list of conditions and the following disclaimer in -** the documentation and/or other materials provided with the -** distribution. -** -** 3 Neither the name of the Standards Of Fundamental Astronomy Board, -** the International Astronomical Union nor the names of its -** contributors may be used to endorse or promote products derived -** from this software without specific prior written permission. -** -** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS -** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT -** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS -** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE -** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, -** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, -** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; -** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER -** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT -** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN -** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE -** POSSIBILITY OF SUCH DAMAGE. -** -*/ |