Fix buffer tests by using more accurate area computation

Author: vissarion

test/algorithms/buffer/buffer_geo_spheroid.cpp

@@ -2,6 +2,8 @@
 // Unit Test
 
 // Copyright (c) 2022 Barend Gehrels, Amsterdam, the Netherlands.
+// Copyright (c) 2023, Oracle and/or its affiliates.
+// Contributed and/or modified by Vissarion Fysikopoulos, 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
@@ -16,6 +18,38 @@ namespace
     std::string const torg = "POINT(10.3937759 63.4302323)";
 }
 
+template
+<
+    typename FormulaPolicy,
+    typename Spheroid,
+    typename CalculationType
+>
+struct geo_buffer_accurate_area
+    : public bg::strategies::buffer::geographic<FormulaPolicy, Spheroid, CalculationType>
+{
+    using base_t = bg::strategies::buffer::geographic<FormulaPolicy, Spheroid, CalculationType>;
+
+public:
+
+    geo_buffer_accurate_area() = default;
+
+    explicit geo_buffer_accurate_area(Spheroid const& spheroid)
+        : base_t(spheroid)
+    {}
+
+    template <typename Geometry>
+    auto area(Geometry const&,
+                std::enable_if_t<! bg::util::is_box<Geometry>::value> * = nullptr) const
+    {
+        return bg::strategy::area::geographic
+            <
+                bg::strategy::karney,
+                bg::strategy::default_order<bg::strategy::karney>::value,
+                Spheroid, CalculationType
+            >(base_t::m_spheroid);
+    }
+};
+
 template <typename Formula, bool Clockwise, typename Point, typename Spheroid>
 void test_linestring(std::string const& label, Spheroid const& spheroid,
                      double expected_area_round, double expected_area_miter)
@@ -25,7 +59,9 @@ void test_linestring(std::string const& label, Spheroid const& spheroid,
 
     ut_settings settings(0.1);
 
-    bg::strategies::buffer::geographic<Formula, Spheroid> strategy(spheroid);
+    using CT = typename bg::coordinate_type<Point>::type;
+    geo_buffer_accurate_area<Formula, Spheroid, CT> strategy(spheroid);
+
     bg::strategy::buffer::geographic_side_straight<Formula, Spheroid> side(spheroid);
     bg::strategy::buffer::geographic_join_miter<Formula, Spheroid> join_miter(spheroid);
     bg::strategy::buffer::geographic_join_round<Formula, Spheroid> join_round(spheroid, points_per_circle);
@@ -45,7 +81,9 @@ void test_point(std::string const& label, Spheroid const& spheroid, double expec
 
     ut_settings settings(0.01);
 
-    bg::strategies::buffer::geographic<Formula, Spheroid> strategy(spheroid);
+    using CT = typename bg::coordinate_type<Point>::type;
+    geo_buffer_accurate_area<Formula, Spheroid, CT> strategy(spheroid);
+
     bg::strategy::buffer::geographic_point_circle<Formula, Spheroid> circle(spheroid, points_per_circle);
 
     // All are ignored for points
@@ -57,24 +95,31 @@ void test_point(std::string const& label, Spheroid const& spheroid, double expec
     test_one_geo<Point, polygon>(label, torg, strategy, side, circle, join_round, end_round, expected_area, 100.0, settings);
 }
 
-int test_main(int, char* [])
+template <typename test_type>
+void test_all()
 {
-    BoostGeometryWriteTestConfiguration();
-
-    using test_type = default_test_type;
-
     using point_t = bg::model::point<test_type, 2, bg::cs::geographic<bg::degree>>;
+    using strategy = bg::strategy::andoyer;
 
     // Use the default spheroid
     bg::srs::spheroid<test_type> def_spheroid;
-    test_linestring<bg::strategy::andoyer, true, point_t>("line_def", def_spheroid, 7996.0, 8093.0);
-    test_point<bg::strategy::andoyer, true, point_t>("point_def", def_spheroid, 31450.0);
+    test_linestring<strategy, true, point_t>("line_def", def_spheroid, 8046.26, 8143.37);
+    test_point<strategy, true, point_t>("point_def", def_spheroid, 31414.36);
 
     // Call it with a quite different spheroid (a near sphere), this changes internal geographic calculations
     // and should result in different areas. Using CSV creation, it's visible in QGis.
     bg::srs::spheroid<test_type> alt_spheroid(6378000.0, 6375000.0);
-    test_linestring<bg::strategy::andoyer, true, point_t>("line_alt", alt_spheroid, 8097.0, 8115.3);
-    test_point<bg::strategy::andoyer, true, point_t>("point_alt", alt_spheroid, 31409.0);
+    test_linestring<strategy, true, point_t>("line_alt", alt_spheroid, 8030.53, 8127.61);
+    test_point<strategy, true, point_t>("point_alt", alt_spheroid, 31414.33);
+}
+
+int test_main(int, char* [])
+{
+    BoostGeometryWriteTestConfiguration();
+
+    // There are several issues with float type such as invalid geometries as output and assertion fails
+    //test_all<float>();
+    test_all<default_test_type>();
 
     return 0;
 }

test/algorithms/buffer/test_buffer.hpp

@@ -156,7 +156,7 @@ struct ut_settings : public ut_base_settings
 
     // Number of points in a circle. Not used for geo tests.
     int points_per_circle;
-    
+
     double multiplier_min_area = 0.95;
     double multiplier_max_area = 1.05;
     double fraction_buffered_points_too_close = 0.10;