58 lines
1.9 KiB
C++
58 lines
1.9 KiB
C++
/*****************************************************************************
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*
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* This file is part of Mapnik (c++ mapping toolkit)
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*
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* Copyright (C) 2006 Artem Pavlenko
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*
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*****************************************************************************/
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//$Id$
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#include <mapnik/distance.hpp>
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#include <mapnik/ellipsoid.hpp>
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#include <cmath>
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namespace mapnik {
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using std::atan2;
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using std::cos;
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using std::pow;
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using std::sin;
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using std::sqrt;
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static const double deg2rad = 0.0174532925199432958;
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static const double R = 6372795.0; // average great-circle radius of the earth
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double great_circle_distance::operator() (coord2d const& pt0,
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coord2d const& pt1) const
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{
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double lon0 = pt0.x * deg2rad;
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double lat0 = pt0.y * deg2rad;
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double lon1 = pt1.x * deg2rad;
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double lat1 = pt1.y * deg2rad;
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double dlat = lat1 - lat0;
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double dlon = lon1 - lon0;
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double sin_dlat = sin(0.5 * dlat);
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double sin_dlon = sin(0.5 * dlon);
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double a = pow(sin_dlat,2.0) + cos(lat0)*cos(lat1)*pow(sin_dlon,2.0);
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double c = 2 * atan2(sqrt(a),sqrt(1 - a));
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return R * c;
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}
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}
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