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- // Boost.Geometry (aka GGL, Generic Geometry Library)
- // Copyright (c) 2007-2012 Barend Gehrels, Amsterdam, the Netherlands.
- // Copyright (c) 2008-2012 Bruno Lalande, Paris, France.
- // Copyright (c) 2009-2012 Mateusz Loskot, London, UK.
- // Use, modification and distribution is subject to the Boost Software License,
- // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
- // http://www.boost.org/LICENSE_1_0.txt)
- //
- // Example: Custom coordinate system example
- #include <iostream>
- #include <boost/geometry/geometry.hpp>
- // 1: declare a coordinate system. For example for Mars
- // Like for the Earth, we let the use choose between degrees or radians
- // (Unfortunately, in real life Mars has two coordinate systems:
- // http://planetarynames.wr.usgs.gov/Page/MARS/system)
- template<typename DegreeOrRadian>
- struct martian
- {
- typedef DegreeOrRadian units;
- };
- // 2: give it also a family
- struct martian_tag;
- // 3: register to which coordinate system family it belongs to
- // this must be done in namespace boost::geometry::traits
- namespace boost { namespace geometry { namespace traits
- {
- template <typename DegreeOrRadian>
- struct cs_tag<martian<DegreeOrRadian> >
- {
- typedef martian_tag type;
- };
- }}} // namespaces
- // NOTE: if the next steps would not be here,
- // compiling a distance function call with martian coordinates
- // would result in a MPL assertion
- // 4: so register a distance strategy as its default strategy
- namespace boost { namespace geometry { namespace strategy { namespace distance { namespace services
- {
- template <typename Point1, typename Point2>
- struct default_strategy<point_tag, point_tag, Point1, Point2, martian_tag, martian_tag>
- {
- typedef haversine<double> type;
- };
- }}}}} // namespaces
- // 5: not worked out. To implement a specific distance strategy for Mars,
- // e.g. with the Mars radius given by default,
- // you will have to implement (/register) several other metafunctions:
- // tag, return_type, similar_type, comparable_type,
- // and structs:
- // get_similar, get_comparable, result_from_distance
- // See e.g. .../boost/geometry/extensions/gis/geographic/strategies/andoyer.hpp
- int main()
- {
- typedef boost::geometry::model::point
- <
- double, 2, martian<boost::geometry::degree>
- > mars_point;
- // Declare two points
- // (Source: http://nssdc.gsfc.nasa.gov/planetary/mars_mileage_guide.html)
- // (Other sources: Wiki and Google give slightly different coordinates, resulting
- // in other distance, 20 km off)
- mars_point viking1(-48.23, 22.54); // Viking 1 landing site in Chryse Planitia
- mars_point pathfinder(-33.55, 19.33); // Pathfinder landing site in Ares Vallis
- double d = boost::geometry::distance(viking1, pathfinder); // Distance in radians on unit-sphere
- // Using the Mars mean radius
- // (Source: http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html)
- std::cout << "Distance between Viking1 and Pathfinder landing sites: "
- << d * 3389.5 << " km" << std::endl;
- // We would get 832.616 here, same order as the 835 (rounded on 5 km) listed
- // on the mentioned site
- #ifdef OPTIONALLY_ELLIPSOIDAL
- // Optionally the distance can be calculated more accurate by an Ellipsoidal approach,
- // giving 834.444 km
- d = boost::geometry::distance(viking1, pathfinder,
- boost::geometry::strategy::distance::andoyer<mars_point>
- (boost::geometry::srs::spheroid<double>(3396.2, 3376.2)));
- std::cout << "Ellipsoidal distance: " << d << " km" << std::endl;
- #endif
- return 0;
- }
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