False self intersection

[jan.kleemann@…]

Please see the following code:

#include <boost/geometry.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/geometries/polygon.hpp>

using namespace boost::geometry;

typedef double FloatType;
typedef model::d2::point_xy<FloatType> Point;
typedef model::polygon<Point> Polygon;
typedef model::multi_polygon<Polygon> MultiPolygon;
typedef model::ring<Point> Ring;
typedef model::box<Point> Box;
typedef model::linestring<Point> LineString;


int main(int argc, char *argv[])
{
   using namespace std;

   Polygon p1;
   boost::geometry::read_wkt("POLYGON((440408.69120520249 5684415.5176829416,"
                                      "440376.96050000004 5684329.5744000003,"
                                      "440376.93154344801 5684329.5945822615,"
                                      "440408.69005920028 5684415.5145825278,"
                                      "440408.69120520249 5684415.5176829416))", p1);

   std::string err;
   bool valid = boost::geometry::is_valid(p1, err);
   cout << "is_valid(p1): " << (valid?"true":"false") << ":\n" << err << endl;

   Polygon p2;
   boost::geometry::read_wkt("POLYGON(("
                             "440408.83723096416 5684415.9121634094,"
                             "440421.56219999958 5684410.6604999993,"
                             "440423.30049999990 5684412.0036999993,"
                             "440439.33189999964 5684394.8839999996,"
                             "440423.75960000046 5684357.4199000001,"
                             "440420.99959999975 5684350.7814000007,"
                             "440404.12129999977 5684310.1740000006,"
                             "440393.24469999969 5684317.6517999992,"
                             "440377.49349999987 5684329.2028999999,"
                             "440376.96050000004 5684329.5744000003,"
                             "440408.69005920028 5684415.5145825278,"
                             "440408.69120520249 5684415.5176829416,"
                             "440408.83689894457 5684415.9118452258,"
                             "440408.83723096416 5684415.9121634094))", p2);

   MultiPolygon mp;
   union_(p1, p2, mp);
   cout << "mp: " << boost::geometry::wkt(mp) << endl;


   return 0;
}

Output:

is_valid(p1): false:
Geometry has invalid self-intersections. A self-intersection point was found at (440409, 5.68442e+006); method: i; operations: i/u; segment IDs {source, multi,
ring, segment}: {0, -1, -1, 0}/{0, -1, -1, 2}
mp: MULTIPOLYGON(((440409 5.68442e+006,440409 5.68442e+006,440377 5.68433e+006,440409 5.68442e+006)))

Both polygons (p1 and p2) are in fact valid, without any self-intersections. But boost.geometry sees one and can't union the two polygons correctly.

Thank you, for the good work.