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Use spheroid instead of sphere for spherical_area() #2470

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Merged
lonvia merged 1 commit into from
May 17, 2026
Merged

Use spheroid instead of sphere for spherical_area() #2470

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10 changes: 4 additions & 6 deletions src/geom-functions.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -369,16 +369,14 @@ namespace {

double spherical_area(polygon_t const &geom)
{
boost::geometry::strategy::area::spherical<> const spherical_earth{
6371008.8};

using sph_point = boost::geometry::model::point<
double, 2,
boost::geometry::cs::spherical_equatorial<boost::geometry::degree>>;
double, 2, boost::geometry::cs::geographic<boost::geometry::degree>>;

boost::geometry::model::polygon<sph_point> sph_geom;
boost::geometry::convert(geom, sph_geom);
return boost::geometry::area(sph_geom, spherical_earth);
return boost::geometry::area(sph_geom,
boost::geometry::strategy::area::geographic<
boost::geometry::strategy::vincenty>{});
}

} // anonymous namespace
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2 changes: 2 additions & 0 deletions tests/test-geom-linestrings.cpp
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Expand Up @@ -55,6 +55,7 @@ TEST_CASE("line geometry", "[NoDB]")
REQUIRE(dimension(geom) == 1);
REQUIRE(num_geometries(geom) == 1);
REQUIRE(area(geom) == Approx(0.0));
REQUIRE(spherical_area(geom) == Approx(0.0));
REQUIRE(length(geom) == Approx(1.41421));
REQUIRE(geometry_type(geom) == "LINESTRING");
REQUIRE(centroid(geom) == geom::geometry_t{geom::point_t{1.5, 1.5}});
Expand Down Expand Up @@ -87,6 +88,7 @@ TEST_CASE("create_linestring from OSM data", "[NoDB]")
REQUIRE(dimension(geom) == 1);
REQUIRE(num_geometries(geom) == 1);
REQUIRE(area(geom) == Approx(0.0));
REQUIRE(spherical_area(geom) == Approx(0.0));
REQUIRE(length(geom) == Approx(1.41421));
REQUIRE(geom.get<geom::linestring_t>() ==
geom::linestring_t{{1, 1}, {2, 2}});
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3 changes: 3 additions & 0 deletions tests/test-geom-multilinestrings.cpp
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Expand Up @@ -35,6 +35,7 @@ TEST_CASE("create_multilinestring with single line", "[NoDB]")
REQUIRE(dimension(geom) == 1);
REQUIRE(num_geometries(geom) == 1);
REQUIRE(area(geom) == Approx(0.0));
REQUIRE(spherical_area(geom) == Approx(0.0));
REQUIRE(length(geom) == Approx(1.0));
auto const &ml = geom.get<geom::multilinestring_t>();
REQUIRE(ml.num_geometries() == 1);
Expand All @@ -60,6 +61,7 @@ TEST_CASE("create_multilinestring with single line and no force_multi",
REQUIRE(geometry_type(geom) == "LINESTRING");
REQUIRE(num_geometries(geom) == 1);
REQUIRE(area(geom) == Approx(0.0));
REQUIRE(spherical_area(geom) == Approx(0.0));
REQUIRE(length(geom) == Approx(1.0));
auto const &l = geom.get<geom::linestring_t>();
REQUIRE(l.num_geometries() == 1);
Expand Down Expand Up @@ -93,6 +95,7 @@ TEST_CASE(
REQUIRE(geometry_type(geom) == "LINESTRING");
REQUIRE(num_geometries(geom) == 1);
REQUIRE(area(geom) == Approx(0.0));
REQUIRE(spherical_area(geom) == Approx(0.0));
REQUIRE(length(geom) == Approx(1.0));
auto const &l = geom.get<geom::linestring_t>();
REQUIRE(l.num_geometries() == 1);
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4 changes: 4 additions & 0 deletions tests/test-geom-multipoints.cpp
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Expand Up @@ -32,6 +32,7 @@ TEST_CASE("multipoint_t with a single point", "[NoDB]")
REQUIRE(dimension(geom) == 0);
REQUIRE(num_geometries(geom) == 1);
REQUIRE(area(geom) == Approx(0.0));
REQUIRE(spherical_area(geom) == Approx(0.0));
REQUIRE(length(geom) == Approx(0.0));
REQUIRE(reverse(geom) == geom);
REQUIRE(centroid(geom) == geom::geometry_t{point});
Expand All @@ -55,6 +56,7 @@ TEST_CASE("multipoint_t with several points", "[NoDB]")
REQUIRE(geometry_type(geom) == "MULTIPOINT");
REQUIRE(num_geometries(geom) == 3);
REQUIRE(area(geom) == Approx(0.0));
REQUIRE(spherical_area(geom) == Approx(0.0));
REQUIRE(length(geom) == Approx(0.0));
REQUIRE(reverse(geom) == geom);
REQUIRE(centroid(geom) == geom::geometry_t{geom::point_t{2, 1}});
Expand Down Expand Up @@ -92,6 +94,7 @@ TEST_CASE("create_multipoint from OSM data", "[NoDB]")
REQUIRE(c[3] == geom::point_t{3, 1});

REQUIRE(area(geom) == Approx(0.0));
REQUIRE(spherical_area(geom) == Approx(0.0));
REQUIRE(length(geom) == Approx(0.0));
REQUIRE(centroid(geom) == geom::geometry_t{geom::point_t{2, 1}});
}
Expand All @@ -118,6 +121,7 @@ TEST_CASE("create_multipoint from OSM data with only a single point", "[NoDB]")
REQUIRE(num_geometries(geom) == 1);
REQUIRE(geom.get<geom::point_t>() == geom::point_t{1, 0});
REQUIRE(area(geom) == Approx(0.0));
REQUIRE(spherical_area(geom) == Approx(0.0));
REQUIRE(length(geom) == Approx(0.0));
REQUIRE(centroid(geom) == geom::geometry_t{geom::point_t{1, 0}});
}
4 changes: 2 additions & 2 deletions tests/test-geom-multipolygons.cpp
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Expand Up @@ -29,7 +29,7 @@ TEST_CASE("multipolygon geometry with single outer, no inner", "[NoDB]")
REQUIRE(dimension(geom) == 2);
REQUIRE(num_geometries(geom) == 1);
REQUIRE(area(geom) == Approx(1.0));
REQUIRE(spherical_area(geom) == Approx(12364031798.5));
REQUIRE(spherical_area(geom) == Approx(12308778361.469454).epsilon(0.00001));
REQUIRE(length(geom) == Approx(0.0));
REQUIRE(centroid(geom) == geom::geometry_t{geom::point_t{0.5, 0.5}});
REQUIRE(geometry_n(geom, 1) ==
Expand Down Expand Up @@ -59,7 +59,7 @@ TEST_CASE("multipolygon geometry with two polygons", "[NoDB]")
REQUIRE(dimension(geom) == 2);
REQUIRE(num_geometries(geom) == 2);
REQUIRE(area(geom) == Approx(9.0));
REQUIRE(spherical_area(geom) == Approx(111106540105.7));
REQUIRE(spherical_area(geom) == Approx(110615268622.783).epsilon(0.00001));
REQUIRE(length(geom) == Approx(0.0));
}

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3 changes: 2 additions & 1 deletion tests/test-geom-null.cpp
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Expand Up @@ -20,7 +20,8 @@ TEST_CASE("null geometry", "[NoDB]")

REQUIRE(dimension(geom) == 0);
REQUIRE(num_geometries(geom) == 0);
REQUIRE(area(geom) == 0.0);
REQUIRE(area(geom) == Approx(0.0));
REQUIRE(spherical_area(geom) == Approx(0.0));
REQUIRE(length(geom) == Approx(0.0));
REQUIRE(geometry_type(geom) == "NULL");
REQUIRE(centroid(geom).is_null());
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1 change: 1 addition & 0 deletions tests/test-geom-points.cpp
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Expand Up @@ -68,6 +68,7 @@ TEST_CASE("create_point from OSM data", "[NoDB]")
REQUIRE(dimension(geom) == 0);
REQUIRE(num_geometries(geom) == 1);
REQUIRE(area(geom) == Approx(0.0));
REQUIRE(spherical_area(geom) == Approx(0.0));
REQUIRE(length(geom) == Approx(0.0));
REQUIRE(centroid(geom) == geom::geometry_t{geom::point_t{1.1, 2.2}});
REQUIRE(geometry_n(geom, 1) == geom);
Expand Down
6 changes: 3 additions & 3 deletions tests/test-geom-polygons.cpp
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Expand Up @@ -25,7 +25,7 @@ TEST_CASE("polygon geometry without inner", "[NoDB]")
REQUIRE(dimension(geom) == 2);
REQUIRE(num_geometries(geom) == 1);
REQUIRE(area(geom) == Approx(1.0));
REQUIRE(spherical_area(geom) == Approx(12364031798.5));
REQUIRE(spherical_area(geom) == Approx(12308778361.469454).epsilon(0.00001));
REQUIRE(length(geom) == Approx(0.0));
REQUIRE(geometry_type(geom) == "POLYGON");
REQUIRE(centroid(geom) == geom::geometry_t{geom::point_t{0.5, 0.5}});
Expand All @@ -41,7 +41,7 @@ TEST_CASE("polygon geometry without inner (reverse)", "[NoDB]")
REQUIRE(dimension(geom) == 2);
REQUIRE(num_geometries(geom) == 1);
REQUIRE(area(geom) == Approx(1.0));
REQUIRE(spherical_area(geom) == Approx(12364031798.5));
REQUIRE(spherical_area(geom) == Approx(12308778361.469454).epsilon(0.00001));
REQUIRE(length(geom) == Approx(0.0));
REQUIRE(geometry_type(geom) == "POLYGON");
REQUIRE(centroid(geom) == geom::geometry_t{geom::point_t{0.5, 0.5}});
Expand All @@ -65,7 +65,7 @@ TEST_CASE("geom::polygon_t", "[NoDB]")
REQUIRE(dimension(geom) == 2);
REQUIRE(num_geometries(geom) == 1);
REQUIRE(area(geom) == Approx(8.0));
REQUIRE(spherical_area(geom) == Approx(98893356298.4));
REQUIRE(spherical_area(geom) == Approx(98452667625.52686).epsilon(0.00001));
REQUIRE(length(geom) == Approx(0.0));
REQUIRE(geometry_type(geom) == "POLYGON");
REQUIRE(centroid(geom) == geom::geometry_t{geom::point_t{1.5, 1.5}});
Expand Down
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