boost::geometry::covered_by wrong results

[Alexander Sarychev <alex-x@…>]

I have a problem with boost::geometry::covered_by method to determine if point is inside polygon or not. In the example below I have point that is exactly out of polygon. Point is far away from polygon by x coordinate (0.1377). The 3rd point of polygon has y-coordinate (4.9999999999999982). And this leads to problem I think. When I change 4.9999999999999982 to 5.00 all is OK. What to do?

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


int main()
{
typedef boost::geometry::model::d2::point_xy<double> bg_point;
typedef boost::geometry::model::polygon< bg_point, false, true > bg_polygon;

// point is tested (out of polygon)
bg_point    p(0.1377, 5.00);

// polygon
bg_polygon  poly;
boost::geometry::read_wkt("POLYGON((0.1277 4.97,  0.1277 5.00, 0.1278 4.9999999999999982, 0.1278 4.97, 0.1277 4.97))", poly);

bool inside;

// inside = true here (ERROR!)
inside = boost::geometry::covered_by(p, poly);

// change 4.9999999999999982 to 5.00
boost::geometry::read_wkt("POLYGON((0.1277 4.97,  0.1277 5.00, 0.1278 5.00, 0.1278 4.97, 0.1277 4.97))", poly);

// inside = false here (OK)
inside = boost::geometry::covered_by(p, poly);

return 0;
}

[Barend Gehrels]

Thanks for the report. Adam, most probably similar problem as you recently solved, can you confirm that? If so, it will be fixed in 1.56

[awulkiew]

Yes, it's fixed. The cause is the same as in ​https://svn.boost.org/trac/boost/ticket/9628.

I also added a test, just in case: ​https://github.com/boostorg/geometry/commit/42cf08658ce632014c14a3bfd70ef020832b296b

Should this be resolved as fixed or duplicate?

[Barend Gehrels]

I would set it to fixed, they have the same cause but this issue states covered_by, the other within, so it is from user-perspective another algorithm that is fixed, and you added a testcase (thanks)