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[area] Addressing comments

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Vissarion Fysikopoulos 2017-01-31 17:55:00 +02:00
parent 930719bad3
commit fd12b69ee6
4 changed files with 9 additions and 298 deletions
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1
include/boost/geometry/strategies/geographic/area_geographic.hpp
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@ -24,7 +24,6 @@ namespace strategy { namespace area
\brief Geographic area calculation by trapezoidal rule plus integral
approximation that gives the ellipsoidal correction
}
*/

288
include/boost/geometry/strategies/spherical/area_huiller.hpp
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@ -1,288 +0,0 @@
// Boost.Geometry (aka GGL, Generic Geometry Library)
// Copyright (c) 2007-2015 Barend Gehrels, Amsterdam, the Netherlands.
// This file was modified by Oracle on 2015, 2016.
// Modifications copyright (c) 2015, 2016 Oracle and/or its affiliates.
// Contributed and/or modified by Vissarion Fysikopoulos, on behalf of Oracle
// Contributed and/or modified by Menelaos Karavelas, on behalf of Oracle
// Contributed and/or modified by Adam Wulkiewicz, on behalf of Oracle
// 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)
#ifndef BOOST_GEOMETRY_STRATEGIES_SPHERICAL_AREA_HUILLER_HPP
#define BOOST_GEOMETRY_STRATEGIES_SPHERICAL_AREA_HUILLER_HPP
#include <boost/geometry/strategies/spherical/distance_haversine.hpp>
#include <boost/geometry/core/radian_access.hpp>
#include <boost/geometry/util/math.hpp>
namespace boost { namespace geometry
{
namespace strategy { namespace area
{
/*!
\brief Area calculation by spherical excess / Huiller's formula
\ingroup strategies
\tparam PointOfSegment point type of segments of rings/polygons
\tparam CalculationType \tparam_calculation
\author Barend Gehrels. Adapted from:
- http://webdocs.cs.ualberta.ca/~graphics/books/GraphicsGems/gemsiv/sph_poly.c
- http://tog.acm.org/resources/GraphicsGems/gemsiv/sph_poly.c
- http://williams.best.vwh.net/avform.htm
\note The version in Graphics Gems IV (page 132-137) didn't account for
polygons crossing the 0 and 180 meridians. The fix for this algorithm
can be found in Graphics Gems V (pages 45-46). See:
- http://kysmykseka.net/koti/wizardry/Game%20Development/Programming/Graphics%20Gems%204.pdf
- http://kysmykseka.net/koti/wizardry/Game%20Development/Programming/Graphics%20Gems%205.pdf
\note This version works for convex and non-convex polygons, for 180 meridian
crossing polygons and for polygons with holes. However, some cases (especially
180 meridian cases) must still be checked.
\note The version which sums angles, which is often seen, doesn't handle non-convex
polygons correctly.
\note The version which sums longitudes, see http://hdl.handle.net/2014/40409,
is simple and works well in most cases but not in 180 meridian crossing cases.
This probably could be solved.
\note This version is made for spherical equatorial coordinate systems
\qbk{
[heading Example]
[area_with_strategy]
[area_with_strategy_output]
[heading See also]
[link geometry.reference.algorithms.area.area_2_with_strategy area (with strategy)]
}
*/
template
<
typename PointOfSegment,
typename CalculationType = void
>
class huiller
{
typedef typename boost::mpl::if_c
<
boost::is_void<CalculationType>::type::value,
typename select_most_precise
<
typename coordinate_type<PointOfSegment>::type,
double
>::type,
CalculationType
>::type calculation_type;
protected :
struct excess_sum
{
calculation_type sum;
calculation_type max_lon, min_lon;
// Distances are calculated on unit sphere here
strategy::distance::haversine<calculation_type> distance_over_unit_sphere;
// Keep track if encircles some pole
size_t crosses_prime_meridian;
bool south; // true if has no point on North hemisphere
bool south_vertex; // true if South pole is a vertex
inline excess_sum()
: sum(0)
, distance_over_unit_sphere(1)
, crosses_prime_meridian(0)
, south(true)
, south_vertex(false)
, max_lon(0)
, min_lon(360)
{}
inline calculation_type area(calculation_type radius) const
{
calculation_type result;
// Encircles pole
if ((crosses_prime_meridian % 2 == 1 && south) || south_vertex)
{
calculation_type constant;
//if(south_vertex)
//{
constant = calculation_type(2) * (max_lon - min_lon)
/ geometry::math::pi<calculation_type>();
//} else {
// constant = 4.0;
//}
if (crosses_prime_meridian % 2 == 0 && crosses_prime_meridian > 1)
{
constant = calculation_type(4) - constant;
}
std::cout << "(const=" << constant << ")";
result = constant
* geometry::math::pi<calculation_type>()
- std::abs(sum);
if (geometry::math::sign<calculation_type>(sum) == -1)
{
result = - result;
}
}
else
{
result = - sum;
}
result *= radius * radius;
return result;
}
};
public :
typedef calculation_type return_type;
typedef PointOfSegment segment_point_type;
typedef excess_sum state_type;
inline huiller(calculation_type radius = 1.0)
: m_radius(radius)
{}
inline void apply(PointOfSegment const& p1,
PointOfSegment const& p2,
excess_sum& state) const
{
if (! geometry::math::equals(get<0>(p1), get<0>(p2)))
{
calculation_type const half = 0.5;
calculation_type const two = 2.0;
calculation_type const four = 4.0;
calculation_type const pi
= geometry::math::pi<calculation_type>();
calculation_type const two_pi
= geometry::math::two_pi<calculation_type>();
calculation_type const half_pi
= geometry::math::half_pi<calculation_type>();
// Distance p1 p2
calculation_type a = state.distance_over_unit_sphere.apply(p1, p2);
// Sides on unit sphere to north pole
calculation_type b = half_pi - geometry::get_as_radian<1>(p2);
calculation_type c = half_pi - geometry::get_as_radian<1>(p1);
// Semi parameter
calculation_type s = half * (a + b + c);
// E: spherical excess, using l'Huiller's formula
// [tg(e / 4)]2 = tg[s / 2] tg[(s-a) / 2] tg[(s-b) / 2] tg[(s-c) / 2]
calculation_type excess = four
* atan(geometry::math::sqrt(geometry::math::abs(tan(s / two)
* tan((s - a) / two)
* tan((s - b) / two)
* tan((s - c) / two))));
excess = geometry::math::abs(excess);
// In right direction: positive, add area. In left direction: negative, subtract area.
// Longitude comparisons are not so obvious. If one is negative and other is positive,
// we have to take the dateline into account.
calculation_type lon_diff = geometry::get_as_radian<0>(p2)
- geometry::get_as_radian<0>(p1);
if (lon_diff <= 0)
{
lon_diff += two_pi;
}
if (lon_diff > pi)
{
excess = -excess;
}
/*
// Keep track whenever a segment crosses the prime meridian
// First normalize to [0,360)
//TODO: compress with trapezoidal strategy
calculation_type p1_lon = geometry::get_as_radian<0>(p1)
- ( floor( geometry::get_as_radian<0>(p1) / two_pi ) * two_pi );
calculation_type p2_lon = geometry::get_as_radian<0>(p2)
- ( floor( geometry::get_as_radian<0>(p2) / two_pi ) * two_pi );
calculation_type max_lon = std::max(p1_lon, p2_lon);
calculation_type min_lon = std::min(p1_lon, p2_lon);
if(max_lon > pi && min_lon < pi && max_lon - min_lon > pi)
{
state.crosses_prime_meridian++;
}
//Test if the segment has a vertex that is the South pole
if (geometry::get_as_radian<1>(p1) == - half_pi
|| geometry::get_as_radian<1>(p2) == - half_pi)
{
state.south_vertex = true;
}
// Global max, min
state.max_lon = std::max(state.max_lon, max_lon);
state.min_lon = std::min(state.min_lon, min_lon);
// Test if the segment has a point on northern hemisphere
if(state.south)
{
if(get<1>(p1) > 0 || get<1>(p2) > 0)
{
state.south = false;
}
}
*/
state.sum += excess;
//std::cout << "(width=" << max_lon-min_lon << ")";
}
}
inline return_type result(excess_sum const& state) const
{
//std::cout << "(pole=" << state.crosses_prime_meridian << ")";
//std::cout<<"(W="<<state.max_lon - state.min_lon<<")";
//std::cout << "(south=" << state.south << ")";
return state.area(m_radius);
}
private :
/// Radius of the sphere
calculation_type m_radius;
};
}} // namespace strategy::area
}} // namespace boost::geometry
#endif // BOOST_GEOMETRY_STRATEGIES_SPHERICAL_AREA_HUILLER_HPP

10
include/boost/geometry/strategies/spherical/area_spherical.hpp
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@ -31,7 +31,7 @@ template
bool LongSegment = false,
typename CalculationType = void
>
class area_spherical
class spherical
{
typedef typename boost::mpl::if_c
<
@ -94,11 +94,11 @@ public :
typedef excess_sum state_type;
typedef geometry::srs::sphere<CT> sphere_type;
inline area_spherical(sphere_type sphere = sphere_type())
inline spherical(sphere_type sphere = sphere_type())
: m_sphere(sphere)
{}
inline area_spherical(CT radius) //backward compatibility
inline spherical(CT radius) //backward compatibility
: m_sphere()
{
m_sphere.set_radius<0>(radius);
@ -140,14 +140,14 @@ namespace services
template <typename Point>
struct default_strategy<spherical_equatorial_tag, Point>
{
typedef strategy::area::area_spherical<Point> type;
typedef strategy::area::spherical<Point> type;
};
// Note: spherical polar coordinate system requires "get_as_radian_equatorial"
template <typename Point>
struct default_strategy<spherical_polar_tag, Point>
{
typedef strategy::area::area_spherical<Point> type;
typedef strategy::area::spherical<Point> type;
};
} // namespace services

8
test/algorithms/area/area_sph_geo.cpp
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@ -61,7 +61,7 @@ void test_spherical_geo()
// calculations splitted for ttmath
std::string poly = "POLYGON((0 0,0 90,90 0,0 0))";
bg::strategy::area::area_spherical
bg::strategy::area::spherical
<
typename bg::point_type<pt>::type
> strategy_unary(1.0);
@ -74,7 +74,7 @@ void test_spherical_geo()
BOOST_CHECK_CLOSE(area, expected, 0.0001);
// With strategy, radius 2 -> 4 pi r^2
bg::strategy::area::area_spherical
bg::strategy::area::spherical
<
typename bg::point_type<pt>::type
> strategy(2.0);
@ -96,7 +96,7 @@ void test_spherical_geo()
// With (spherical) Earth strategy
poly = "POLYGON((-178.7858 70.7852, 177.4758 71.2333, 179.7436 71.5733, -178.7858 70.7852))";
bg::strategy::area::area_spherical
bg::strategy::area::spherical
<
typename bg::point_type<pt>::type
> spherical_earth(6373);
@ -373,7 +373,7 @@ void test_spherical_geo()
}
bg::correct(aurha);
}*/
bg::strategy::area::area_spherical
bg::strategy::area::spherical
<
typename bg::point_type<pt>::type
> area_spherical(6372.795);