| 1 | #include "erfa.h"
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| 2 |
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| 3 | void eraAtoiq(const char *type,
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| 4 | double ob1, double ob2, eraASTROM *astrom,
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| 5 | double *ri, double *di)
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| 6 | /*
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| 7 | ** - - - - - - - - -
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| 8 | ** e r a A t o i q
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| 9 | ** - - - - - - - - -
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| 10 | **
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| 11 | ** Quick observed place to CIRS, given the star-independent astrometry
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| 12 | ** parameters.
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| 13 | **
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| 14 | ** Use of this function is appropriate when efficiency is important and
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| 15 | ** where many star positions are all to be transformed for one date.
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| 16 | ** The star-independent astrometry parameters can be obtained by
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| 17 | ** calling eraApio[13] or eraApco[13].
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| 18 | **
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| 19 | ** Given:
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| 20 | ** type char[] type of coordinates: "R", "H" or "A" (Note 1)
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| 21 | ** ob1 double observed Az, HA or RA (radians; Az is N=0,E=90)
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| 22 | ** ob2 double observed ZD or Dec (radians)
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| 23 | ** astrom eraASTROM* star-independent astrometry parameters:
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| 24 | ** pmt double PM time interval (SSB, Julian years)
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| 25 | ** eb double[3] SSB to observer (vector, au)
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| 26 | ** eh double[3] Sun to observer (unit vector)
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| 27 | ** em double distance from Sun to observer (au)
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| 28 | ** v double[3] barycentric observer velocity (vector, c)
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| 29 | ** bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor
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| 30 | ** bpn double[3][3] bias-precession-nutation matrix
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| 31 | ** along double longitude + s' (radians)
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| 32 | ** xpl double polar motion xp wrt local meridian (radians)
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| 33 | ** ypl double polar motion yp wrt local meridian (radians)
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| 34 | ** sphi double sine of geodetic latitude
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| 35 | ** cphi double cosine of geodetic latitude
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| 36 | ** diurab double magnitude of diurnal aberration vector
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| 37 | ** eral double "local" Earth rotation angle (radians)
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| 38 | ** refa double refraction constant A (radians)
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| 39 | ** refb double refraction constant B (radians)
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| 40 | **
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| 41 | ** Returned:
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| 42 | ** ri double* CIRS right ascension (CIO-based, radians)
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| 43 | ** di double* CIRS declination (radians)
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| 44 | **
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| 45 | ** Notes:
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| 46 | **
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| 47 | ** 1) "Observed" Az,El means the position that would be seen by a
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| 48 | ** perfect geodetically aligned theodolite. This is related to
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| 49 | ** the observed HA,Dec via the standard rotation, using the geodetic
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| 50 | ** latitude (corrected for polar motion), while the observed HA and
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| 51 | ** RA are related simply through the Earth rotation angle and the
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| 52 | ** site longitude. "Observed" RA,Dec or HA,Dec thus means the
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| 53 | ** position that would be seen by a perfect equatorial with its
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| 54 | ** polar axis aligned to the Earth's axis of rotation. By removing
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| 55 | ** from the observed place the effects of atmospheric refraction and
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| 56 | ** diurnal aberration, the CIRS RA,Dec is obtained.
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| 57 | **
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| 58 | ** 2) Only the first character of the type argument is significant.
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| 59 | ** "R" or "r" indicates that ob1 and ob2 are the observed right
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| 60 | ** ascension and declination; "H" or "h" indicates that they are
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| 61 | ** hour angle (west +ve) and declination; anything else ("A" or
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| 62 | ** "a" is recommended) indicates that ob1 and ob2 are azimuth (north
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| 63 | ** zero, east 90 deg) and zenith distance. (Zenith distance is used
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| 64 | ** rather than altitude in order to reflect the fact that no
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| 65 | ** allowance is made for depression of the horizon.)
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| 66 | **
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| 67 | ** 3) The accuracy of the result is limited by the corrections for
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| 68 | ** refraction, which use a simple A*tan(z) + B*tan^3(z) model.
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| 69 | ** Providing the meteorological parameters are known accurately and
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| 70 | ** there are no gross local effects, the predicted observed
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| 71 | ** coordinates should be within 0.05 arcsec (optical) or 1 arcsec
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| 72 | ** (radio) for a zenith distance of less than 70 degrees, better
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| 73 | ** than 30 arcsec (optical or radio) at 85 degrees and better than
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| 74 | ** 20 arcmin (optical) or 30 arcmin (radio) at the horizon.
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| 75 | **
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| 76 | ** Without refraction, the complementary functions eraAtioq and
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| 77 | ** eraAtoiq are self-consistent to better than 1 microarcsecond all
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| 78 | ** over the celestial sphere. With refraction included, consistency
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| 79 | ** falls off at high zenith distances, but is still better than
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| 80 | ** 0.05 arcsec at 85 degrees.
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| 81 | **
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| 82 | ** 4) It is advisable to take great care with units, as even unlikely
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| 83 | ** values of the input parameters are accepted and processed in
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| 84 | ** accordance with the models used.
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| 85 | **
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| 86 | ** Called:
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| 87 | ** eraS2c spherical coordinates to unit vector
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| 88 | ** eraC2s p-vector to spherical
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| 89 | ** eraAnp normalize angle into range 0 to 2pi
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| 90 | **
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| 91 | ** Copyright (C) 2013-2015, NumFOCUS Foundation.
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| 92 | ** Derived, with permission, from the SOFA library. See notes at end of file.
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| 93 | */
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| 94 | {
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| 95 | int c;
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| 96 | double c1, c2, sphi, cphi, ce, xaeo, yaeo, zaeo, v[3],
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| 97 | xmhdo, ymhdo, zmhdo, az, sz, zdo, refa, refb, tz, dref,
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| 98 | zdt, xaet, yaet, zaet, xmhda, ymhda, zmhda,
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| 99 | f, xhd, yhd, zhd, xpl, ypl, w, hma;
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| 100 |
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| 101 | /* Coordinate type. */
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| 102 | c = (int) type[0];
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| 103 |
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| 104 | /* Coordinates. */
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| 105 | c1 = ob1;
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| 106 | c2 = ob2;
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| 107 |
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| 108 | /* Sin, cos of latitude. */
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| 109 | sphi = astrom->sphi;
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| 110 | cphi = astrom->cphi;
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| 111 |
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| 112 | /* Standardize coordinate type. */
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| 113 | if ( c == 'r' || c == 'R' ) {
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| 114 | c = 'R';
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| 115 | } else if ( c == 'h' || c == 'H' ) {
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| 116 | c = 'H';
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| 117 | } else {
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| 118 | c = 'A';
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| 119 | }
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| 120 |
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| 121 | /* If Az,ZD, convert to Cartesian (S=0,E=90). */
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| 122 | if ( c == 'A' ) {
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| 123 | ce = sin(c2);
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| 124 | xaeo = - cos(c1) * ce;
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| 125 | yaeo = sin(c1) * ce;
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| 126 | zaeo = cos(c2);
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| 127 |
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| 128 | } else {
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| 129 |
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| 130 | /* If RA,Dec, convert to HA,Dec. */
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| 131 | if ( c == 'R' ) c1 = astrom->eral - c1;
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| 132 |
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| 133 | /* To Cartesian -HA,Dec. */
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| 134 | eraS2c ( -c1, c2, v );
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| 135 | xmhdo = v[0];
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| 136 | ymhdo = v[1];
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| 137 | zmhdo = v[2];
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| 138 |
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| 139 | /* To Cartesian Az,El (S=0,E=90). */
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| 140 | xaeo = sphi*xmhdo - cphi*zmhdo;
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| 141 | yaeo = ymhdo;
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| 142 | zaeo = cphi*xmhdo + sphi*zmhdo;
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| 143 | }
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| 144 |
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| 145 | /* Azimuth (S=0,E=90). */
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| 146 | az = ( xaeo != 0.0 || yaeo != 0.0 ) ? atan2(yaeo,xaeo) : 0.0;
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| 147 |
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| 148 | /* Sine of observed ZD, and observed ZD. */
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| 149 | sz = sqrt ( xaeo*xaeo + yaeo*yaeo );
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| 150 | zdo = atan2 ( sz, zaeo );
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| 151 |
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| 152 | /*
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| 153 | ** Refraction
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| 154 | ** ----------
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| 155 | */
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| 156 |
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| 157 | /* Fast algorithm using two constant model. */
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| 158 | refa = astrom->refa;
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| 159 | refb = astrom->refb;
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| 160 | tz = sz / zaeo;
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| 161 | dref = ( refa + refb*tz*tz ) * tz;
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| 162 | zdt = zdo + dref;
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| 163 |
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| 164 | /* To Cartesian Az,ZD. */
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| 165 | ce = sin(zdt);
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| 166 | xaet = cos(az) * ce;
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| 167 | yaet = sin(az) * ce;
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| 168 | zaet = cos(zdt);
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| 169 |
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| 170 | /* Cartesian Az,ZD to Cartesian -HA,Dec. */
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| 171 | xmhda = sphi*xaet + cphi*zaet;
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| 172 | ymhda = yaet;
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| 173 | zmhda = - cphi*xaet + sphi*zaet;
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| 174 |
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| 175 | /* Diurnal aberration. */
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| 176 | f = ( 1.0 + astrom->diurab*ymhda );
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| 177 | xhd = f * xmhda;
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| 178 | yhd = f * ( ymhda - astrom->diurab );
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| 179 | zhd = f * zmhda;
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| 180 |
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| 181 | /* Polar motion. */
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| 182 | xpl = astrom->xpl;
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| 183 | ypl = astrom->ypl;
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| 184 | w = xpl*xhd - ypl*yhd + zhd;
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| 185 | v[0] = xhd - xpl*w;
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| 186 | v[1] = yhd + ypl*w;
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| 187 | v[2] = w - ( xpl*xpl + ypl*ypl ) * zhd;
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| 188 |
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| 189 | /* To spherical -HA,Dec. */
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| 190 | eraC2s(v, &hma, di);
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| 191 |
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| 192 | /* Right ascension. */
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| 193 | *ri = eraAnp(astrom->eral + hma);
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| 194 |
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| 195 | /* Finished. */
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| 196 |
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| 197 | }
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| 198 | /*----------------------------------------------------------------------
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| 199 | **
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| 200 | **
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| 201 | ** Copyright (C) 2013-2015, NumFOCUS Foundation.
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| 202 | ** All rights reserved.
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| 203 | **
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| 204 | ** This library is derived, with permission, from the International
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| 205 | ** Astronomical Union's "Standards of Fundamental Astronomy" library,
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| 206 | ** available from http://www.iausofa.org.
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| 207 | **
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| 208 | ** The ERFA version is intended to retain identical functionality to
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| 209 | ** the SOFA library, but made distinct through different function and
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| 210 | ** file names, as set out in the SOFA license conditions. The SOFA
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| 211 | ** original has a role as a reference standard for the IAU and IERS,
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| 212 | ** and consequently redistribution is permitted only in its unaltered
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| 213 | ** state. The ERFA version is not subject to this restriction and
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| 214 | ** therefore can be included in distributions which do not support the
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| 215 | ** concept of "read only" software.
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| 216 | **
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| 217 | ** Although the intent is to replicate the SOFA API (other than
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| 218 | ** replacement of prefix names) and results (with the exception of
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| 219 | ** bugs; any that are discovered will be fixed), SOFA is not
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| 220 | ** responsible for any errors found in this version of the library.
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| 221 | **
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| 222 | ** If you wish to acknowledge the SOFA heritage, please acknowledge
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| 223 | ** that you are using a library derived from SOFA, rather than SOFA
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| 224 | ** itself.
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| 225 | **
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| 226 | **
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| 227 | ** TERMS AND CONDITIONS
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| 228 | **
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| 229 | ** Redistribution and use in source and binary forms, with or without
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| 230 | ** modification, are permitted provided that the following conditions
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| 231 | ** are met:
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| 232 | **
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| 233 | ** 1 Redistributions of source code must retain the above copyright
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| 234 | ** notice, this list of conditions and the following disclaimer.
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| 235 | **
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| 236 | ** 2 Redistributions in binary form must reproduce the above copyright
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| 237 | ** notice, this list of conditions and the following disclaimer in
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| 238 | ** the documentation and/or other materials provided with the
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| 239 | ** distribution.
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| 240 | **
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| 241 | ** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
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| 242 | ** the International Astronomical Union nor the names of its
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| 243 | ** contributors may be used to endorse or promote products derived
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| 244 | ** from this software without specific prior written permission.
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| 245 | **
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| 246 | ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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| 247 | ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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| 248 | ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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| 249 | ** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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| 250 | ** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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| 251 | ** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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| 252 | ** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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| 253 | ** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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| 254 | ** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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| 255 | ** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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| 256 | ** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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| 257 | ** POSSIBILITY OF SUCH DAMAGE.
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| 258 | **
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| 259 | */
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