projections/impl/pj_qsfn.hpp

0001 // Boost.Geometry (aka GGL, Generic Geometry Library)
0002 // This file is manually converted from PROJ4
0003
0004 // Copyright (c) 2008-2012 Barend Gehrels, Amsterdam, the Netherlands.
0005
0006 // This file was modified by Oracle on 2017.
0007 // Modifications copyright (c) 2017, Oracle and/or its affiliates.
0008 // Contributed and/or modified by Adam Wulkiewicz, on behalf of Oracle
0009
0010 // Use, modification and distribution is subject to the Boost Software License,
0011 // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
0012 // http://www.boost.org/LICENSE_1_0.txt)
0013
0014 // This file is converted from PROJ4, http://trac.osgeo.org/proj
0015 // PROJ4 is originally written by Gerald Evenden (then of the USGS)
0016 // PROJ4 is maintained by Frank Warmerdam
0017 // PROJ4 is converted to Geometry Library by Barend Gehrels (Geodan, Amsterdam)
0018
0019 // Original copyright notice:
0020
0021 // Permission is hereby granted, free of charge, to any person obtaining a
0022 // copy of this software and associated documentation files (the "Software"),
0023 // to deal in the Software without restriction, including without limitation
0024 // the rights to use, copy, modify, merge, publish, distribute, sublicense,
0025 // and/or sell copies of the Software, and to permit persons to whom the
0026 // Software is furnished to do so, subject to the following conditions:
0027
0028 // The above copyright notice and this permission notice shall be included
0029 // in all copies or substantial portions of the Software.
0030
0031 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
0032 // OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
0033 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
0034 // THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
0035 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
0036 // FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
0037 // DEALINGS IN THE SOFTWARE.
0038
0039 #ifndef BOOST_GEOMETRY_PROJECTIONS_PJ_QSFN_HPP
0040 #define BOOST_GEOMETRY_PROJECTIONS_PJ_QSFN_HPP
0041
0042
0043 namespace boost { namespace geometry { namespace projections
0044 {
0045
0046 namespace detail {
0047
0048 /* determine small q */
0049 template <typename T>
0050 inline T pj_qsfn(T const& sinphi, T const& e, T const& one_es)
0051 {
0052     static const T EPSILON = 1.0e-7;
0053
0054     if (e >= EPSILON)
0055     {
0056         T con = e * sinphi;
0057         return (one_es * (sinphi / (1. - con * con) -
0058            (.5 / e) * log ((1. - con) / (1. + con))));
0059     } else
0060         return (sinphi + sinphi);
0061 }
0062
0063
0064 static const int MAX_C = 9;
0065
0066 template <typename T>
0067 struct AUTHALIC
0068 {
0069     T C[MAX_C], CP[MAX_C], CQ[MAX_C];
0070 };
0071
0072 /**
0073  * @brief determine authalic latitude
0074  * @param[in] phi geographic latitude
0075  * @param[in] a initialized structure pointer
0076  * @return authalic latitude
0077  */
0078 template <typename T>
0079 inline T proj_qsfn(T const& phi, AUTHALIC<T> const& a)
0080 {
0081     T s, s2, sum;
0082     int i = MAX_C;
0083
0084     s = sin(phi);
0085     s2 = s * s;
0086     sum = a.CQ[MAX_C - 1];
0087     while (--i) sum = a.CQ[i] + s2 * sum;
0088     return(s * sum);
0089 }
0090
0091 } // namespace detail
0092
0093 }}} // namespace boost::geometry::projections
0094
0095 #endif