[Jts-topo-suite-user] issue with Geometry.union

[Tomas F <tof...@gm...>]

Hi, I have encountered a result when running Geometry.union which I think
is incorrect. There are parts of the input
to union that aren't contained in the resulting geometry.

The following program reproduces the issue:

{
        WKTReader reader = new WKTReader();

        com.vividsolutions.jts.geom.Polygon p1 =
(com.vividsolutions.jts.geom.Polygon) reader.read("POLYGON ((42.975 -92.25,
100.0 0.0, -200.0 0.0, 126.0 -184.5, 42.975 -92.25))");
        com.vividsolutions.jts.geom.Polygon p2 =
(com.vividsolutions.jts.geom.Polygon) reader.read("POLYGON ((126.0 -184.5,
-9.0 -34.5, -200.0 -300.0, 126.0 -184.5))");

        assert p1.isValid();
        assert p2.isValid();

        Geometry union = p1.union(p2);

        double distance0 = union.distance(new
GeometryFactory().createPoint(p1.getCoordinates()[0]));
        double distance1 = union.distance(new
GeometryFactory().createPoint(p1.getCoordinates()[1]));
        double distance2 = union.distance(new
GeometryFactory().createPoint(p1.getCoordinates()[2]));
        double distance3 = union.distance(new
GeometryFactory().createPoint(p1.getCoordinates()[3]));

        System.out.println("Distance from point to union: "+distance0);
        System.out.println("Distance from point to union: "+distance1);
        System.out.println("Distance from point to union: "+distance2);
        System.out.println("Distance from point to union: "+distance3);

        assert union.covers(p1) : "(p1 U p2) must cover p1";
        assert union.covers(p2) : "(p1 U p2) union must cover p2";
    }

Output:

Distance from point to union: 0.0
Distance from point to union: 104.09834518191563
Distance from point to union: 175.19474956680358
Distance from point to union: 0.0
java.lang.AssertionError: (p1 U p2) must cover p1

Best regards
/Tomas