FACT++  1.0
gd2gce.c
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1 #include "erfa.h"
2 
3 int eraGd2gce ( double a, double f, double elong, double phi,
4  double height, double xyz[3] )
5 /*
6 ** - - - - - - - - - -
7 ** e r a G d 2 g c e
8 ** - - - - - - - - - -
9 **
10 ** Transform geodetic coordinates to geocentric for a reference
11 ** ellipsoid of specified form.
12 **
13 ** Given:
14 ** a double equatorial radius (Notes 1,4)
15 ** f double flattening (Notes 2,4)
16 ** elong double longitude (radians, east +ve)
17 ** phi double latitude (geodetic, radians, Note 4)
18 ** height double height above ellipsoid (geodetic, Notes 3,4)
19 **
20 ** Returned:
21 ** xyz double[3] geocentric vector (Note 3)
22 **
23 ** Returned (function value):
24 ** int status: 0 = OK
25 ** -1 = illegal case (Note 4)
26 ** Notes:
27 **
28 ** 1) The equatorial radius, a, can be in any units, but meters is
29 ** the conventional choice.
30 **
31 ** 2) The flattening, f, is (for the Earth) a value around 0.00335,
32 ** i.e. around 1/298.
33 **
34 ** 3) The equatorial radius, a, and the height, height, must be
35 ** given in the same units, and determine the units of the
36 ** returned geocentric vector, xyz.
37 **
38 ** 4) No validation is performed on individual arguments. The error
39 ** status -1 protects against (unrealistic) cases that would lead
40 ** to arithmetic exceptions. If an error occurs, xyz is unchanged.
41 **
42 ** 5) The inverse transformation is performed in the function
43 ** eraGc2gde.
44 **
45 ** 6) The transformation for a standard ellipsoid (such as ERFA_WGS84) can
46 ** more conveniently be performed by calling eraGd2gc, which uses a
47 ** numerical code to identify the required a and f values.
48 **
49 ** References:
50 **
51 ** Green, R.M., Spherical Astronomy, Cambridge University Press,
52 ** (1985) Section 4.5, p96.
53 **
54 ** Explanatory Supplement to the Astronomical Almanac,
55 ** P. Kenneth Seidelmann (ed), University Science Books (1992),
56 ** Section 4.22, p202.
57 **
58 ** Copyright (C) 2013-2015, NumFOCUS Foundation.
59 ** Derived, with permission, from the SOFA library. See notes at end of file.
60 */
61 {
62  double sp, cp, w, d, ac, as, r;
63 
64 /* Functions of geodetic latitude. */
65  sp = sin(phi);
66  cp = cos(phi);
67  w = 1.0 - f;
68  w = w * w;
69  d = cp*cp + w*sp*sp;
70  if ( d <= 0.0 ) return -1;
71  ac = a / sqrt(d);
72  as = w * ac;
73 
74 /* Geocentric vector. */
75  r = (ac + height) * cp;
76  xyz[0] = r * cos(elong);
77  xyz[1] = r * sin(elong);
78  xyz[2] = (as + height) * sp;
79 
80 /* Success. */
81  return 0;
82 
83 }
84 /*----------------------------------------------------------------------
85 **
86 **
87 ** Copyright (C) 2013-2015, NumFOCUS Foundation.
88 ** All rights reserved.
89 **
90 ** This library is derived, with permission, from the International
91 ** Astronomical Union's "Standards of Fundamental Astronomy" library,
92 ** available from http://www.iausofa.org.
93 **
94 ** The ERFA version is intended to retain identical functionality to
95 ** the SOFA library, but made distinct through different function and
96 ** file names, as set out in the SOFA license conditions. The SOFA
97 ** original has a role as a reference standard for the IAU and IERS,
98 ** and consequently redistribution is permitted only in its unaltered
99 ** state. The ERFA version is not subject to this restriction and
100 ** therefore can be included in distributions which do not support the
101 ** concept of "read only" software.
102 **
103 ** Although the intent is to replicate the SOFA API (other than
104 ** replacement of prefix names) and results (with the exception of
105 ** bugs; any that are discovered will be fixed), SOFA is not
106 ** responsible for any errors found in this version of the library.
107 **
108 ** If you wish to acknowledge the SOFA heritage, please acknowledge
109 ** that you are using a library derived from SOFA, rather than SOFA
110 ** itself.
111 **
112 **
113 ** TERMS AND CONDITIONS
114 **
115 ** Redistribution and use in source and binary forms, with or without
116 ** modification, are permitted provided that the following conditions
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118 **
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120 ** notice, this list of conditions and the following disclaimer.
121 **
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126 **
127 ** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
128 ** the International Astronomical Union nor the names of its
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133 ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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145 */
eraGd2gce
int eraGd2gce(double a, double f, double elong, double phi, double height, double xyz[3])
Definition: gd2gce.c:3
height
float height
Definition: HeadersGPS.h:26