Difference problem

[grizoood]

Hello, I am having a problem using the Difference function. Here is a code snippet to show the different results:

var precisionModel = new PrecisionModel(PrecisionModels.Floating);
var ntsGeometryServices = new NtsGeometryServices(
                   CoordinateArraySequenceFactory.Instance,
                   precisionModel,
                   NtsGeometryServices.Instance.DefaultSRID,
                   GeometryOverlay.NG,
                   new CoordinateEqualityComparer());
var factory = ntsGeometryServices.CreateGeometryFactory();

var seg1 = new LineSegment(new Coordinate(56.505308802306047, -9.7735522481500272), new Coordinate(61.658255026265437, -2.4143823696501023));
var seg2 = new LineSegment(new Coordinate(56.505308802306047, -9.773552248150029), new Coordinate(57.678138451727747, -8.0985779221024536));

var line1 = seg1.ToGeometry(factory);
// LINESTRING (56.505308802306047 -9.7735522481500272, 61.658255026265437 -2.4143823696501023)
var line2 = seg2.ToGeometry(factory);
// LINESTRING (56.505308802306047 -9.773552248150029, 57.678138451727747 -8.0985779221024536)

var pmReduce = new PrecisionModel(1.0e2);
line1 = GeometryPrecisionReducer.Reduce(line1, pmReduce) as LineString;
// LINESTRING (56.51 -9.77, 61.66 -2.41)
line2 = GeometryPrecisionReducer.Reduce(line2, pmReduce) as LineString;
// LINESTRING (56.51 -9.77, 57.68 -8.1)

var diff = line1.Difference(line2);
// LINESTRING (56.51 -9.77, 61.66 -2.41)

var oNG = new OverlayNG(line1, line2, pmReduce, NetTopologySuite.Operation.Overlay.SpatialFunction.Difference);
var diff2 = oNG.GetResult();
// LINESTRING (57.68 -8.1, 61.66 -2.41)

The geometry diff and diff2 do not match, I expect the result of diff to be equal to the result of diff2. It looks like
Geometry diff = line1.Difference(line2); keeps the precision entered during the first creation.

Should I use new OverlayNG(…) to perform this processing