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Diffstat (limited to 'ast/erfa/gd2gce.c')
| -rw-r--r-- | ast/erfa/gd2gce.c | 146 |
1 files changed, 146 insertions, 0 deletions
diff --git a/ast/erfa/gd2gce.c b/ast/erfa/gd2gce.c new file mode 100644 index 0000000..5aae512 --- /dev/null +++ b/ast/erfa/gd2gce.c @@ -0,0 +1,146 @@ +#include "erfa.h" + +int eraGd2gce ( double a, double f, double elong, double phi, + double height, double xyz[3] ) +/* +** - - - - - - - - - - +** e r a G d 2 g c e +** - - - - - - - - - - +** +** Transform geodetic coordinates to geocentric for a reference +** ellipsoid of specified form. +** +** Given: +** a double equatorial radius (Notes 1,4) +** f double flattening (Notes 2,4) +** elong double longitude (radians, east +ve) +** phi double latitude (geodetic, radians, Note 4) +** height double height above ellipsoid (geodetic, Notes 3,4) +** +** Returned: +** xyz double[3] geocentric vector (Note 3) +** +** Returned (function value): +** int status: 0 = OK +** -1 = illegal case (Note 4) +** Notes: +** +** 1) The equatorial radius, a, can be in any units, but meters is +** the conventional choice. +** +** 2) The flattening, f, is (for the Earth) a value around 0.00335, +** i.e. around 1/298. +** +** 3) The equatorial radius, a, and the height, height, must be +** given in the same units, and determine the units of the +** returned geocentric vector, xyz. +** +** 4) No validation is performed on individual arguments. The error +** status -1 protects against (unrealistic) cases that would lead +** to arithmetic exceptions. If an error occurs, xyz is unchanged. +** +** 5) The inverse transformation is performed in the function +** eraGc2gde. +** +** 6) The transformation for a standard ellipsoid (such as ERFA_WGS84) can +** more conveniently be performed by calling eraGd2gc, which uses a +** numerical code to identify the required a and f values. +** +** References: +** +** Green, R.M., Spherical Astronomy, Cambridge University Press, +** (1985) Section 4.5, p96. +** +** Explanatory Supplement to the Astronomical Almanac, +** P. Kenneth Seidelmann (ed), University Science Books (1992), +** Section 4.22, p202. +** +** Copyright (C) 2013-2014, NumFOCUS Foundation. +** Derived, with permission, from the SOFA library. See notes at end of file. +*/ +{ + double sp, cp, w, d, ac, as, r; + + +/* Functions of geodetic latitude. */ + sp = sin(phi); + cp = cos(phi); + w = 1.0 - f; + w = w * w; + d = cp*cp + w*sp*sp; + if ( d <= 0.0 ) return -1; + ac = a / sqrt(d); + as = w * ac; + +/* Geocentric vector. */ + r = (ac + height) * cp; + xyz[0] = r * cos(elong); + xyz[1] = r * sin(elong); + xyz[2] = (as + height) * sp; + +/* Success. */ + return 0; + +} +/*---------------------------------------------------------------------- +** +** +** Copyright (C) 2013-2014, 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. +** +*/ |