Math transform bug

[HarelM]

The following is the code I'm using to create a math transform:

        public static IMathTransform Create()
        {
            var coordinateTransformFactory = new CoordinateTransformationFactory();
            var coordinateSystemFactory = new CoordinateSystemFactory();
            var itmParameters = new List<ProjectionParameter>
            {
                new ProjectionParameter("latitude_of_origin", 31.734393611111109123611111111111),
                new ProjectionParameter("central_meridian", 35.204516944444442572222222222222),
                new ProjectionParameter("false_northing", 626907.390),
                new ProjectionParameter("false_easting", 219529.584),
                new ProjectionParameter("scale_factor", 1.0000067)
            };

            var itmDatum = coordinateSystemFactory.CreateHorizontalDatum("Isreal 1993", DatumType.HD_Geocentric,
                Ellipsoid.GRS80, new Wgs84ConversionInfo(-24.0024, -17.1032, -17.8444, -0.33077, -1.85269, 1.66969, 5.4248));

            var itmGeo = coordinateSystemFactory.CreateGeographicCoordinateSystem("ITM", AngularUnit.Degrees, itmDatum,
                PrimeMeridian.Greenwich, new AxisInfo("East", AxisOrientationEnum.East), new AxisInfo("North", AxisOrientationEnum.North));

            var itmProjection = coordinateSystemFactory.CreateProjection("Transverse_Mercator", "Transverse_Mercator", itmParameters);
            var itm = coordinateSystemFactory.CreateProjectedCoordinateSystem("ITM", itmGeo, itmProjection, LinearUnit.Metre,
                new AxisInfo("East", AxisOrientationEnum.East), new AxisInfo("North", AxisOrientationEnum.North));

            var wgs84 = ProjectedCoordinateSystem.WGS84_UTM(36, true).GeographicCoordinateSystem;
            return coordinateTransformFactory.CreateFromCoordinateSystems(itm, wgs84).MathTransform;
        }

The following is the code, when I tried to run it from immediate window , _itmWgs84MathTransform is the an instance created with the above factory:

_itmWgs84MathTransform.Transform(new Coordinate(200000,600000))
Correct results:
{(34.999654105859982, 31.491929780294662, NaN)}
    CoordinateValue: {(34.999654105859982, 31.491929780294662, NaN)}
    X: 34.999654105859982
    Y: 31.491929780294662
    Z: NaN
_itmWgs84MathTransform.Inverse().Transform(new Coordinate(35,32))
Correct results:
{(200138.59858848609, 656336.21658061759, NaN)}
    CoordinateValue: {(200138.59858848609, 656336.21658061759, NaN)}
    X: 200138.59858848609
    Y: 656336.21658061759
    Z: NaN
Instance is now corrupted:
_itmWgs84MathTransform.Transform(new Coordinate(200000,600000))
Bad results:
{(2.9315235171991696, -27.2988002073075, NaN)}
    CoordinateValue: {(2.9315235171991696, -27.2988002073075, NaN)}
    X: 2.9315235171991696
    Y: -27.2988002073075
    Z: NaN

BTW calling the following code fixes the issue:
_itmWgs84MathTransform.Inverse().Inverse()

I can probably send a pull request if needed, assuming someone will direct me to the right place to look for this.

[HarelM]

Further debug reveals the following in ConcatenatedTransform:
Items in the list are not cloned:

                public ConcatenatedTransform Clone()
		{
			var clonedList = new List<ICoordinateTransformation>(_coordinateTransformationList.Count);
			foreach (ICoordinateTransformation ct in _coordinateTransformationList)
				clonedList.Add(ct);
			return new ConcatenatedTransform(clonedList);
		}

Which causes the invert function to invert their math transform on the newly created instance:

		public override void Invert()
		{
			_coordinateTransformationList.Reverse();
			foreach (ICoordinateTransformation ic in _coordinateTransformationList)
				ic.MathTransform.Invert();
		}

I couldn't find a clone method ICoordinateTransformation, any thoughts?

[FObermaier]

Using IMathTransform.Inverse() is known to be flaky.
Modify your factory IMathTransform Create() function to return either forward or inverse math transform objects and use those instead of Inverse().

[HarelM]

This is my plan in order to workaround this issue, but fixing it inside this library is important in order for other people not to experience this issue.