/// <summary>
/// Performs an OSGB36/ODN to ETRS89 datum transformation. Accuracy is approximately 10 centimeters.
/// Whilst very accurate this method is much slower than the Helmert transformation.
/// </summary>
public static LatitudeLongitude OsgbToEtrs89(Osgb36 coordinates, OstnVersionEnum ostnVersion = OstnVersionEnum.OSTN15)
{
//calculate shifts from OSGB36 point
double errorN = double.MaxValue;
double errorE = double.MaxValue;
EastingNorthing enCoordinates = null;
Shifts shiftsA = GetShifts(coordinates, ostnVersion);
//0.0001 error meters
int iter = 0;
while ((errorN > 0.0001 || errorE > 0.0001) && iter < 10)
{
enCoordinates = new EastingNorthing(coordinates.Easting - shiftsA.Se, coordinates.Northing - shiftsA.Sn);
Shifts shiftsB = GetShifts(enCoordinates, ostnVersion);
errorE = Math.Abs(shiftsA.Se - shiftsB.Se);
errorN = Math.Abs(shiftsA.Sn - shiftsB.Sn);
shiftsA = shiftsB;
iter++;
}
return(Convert.ToLatitudeLongitude(new Wgs84(), new BritishNationalGrid(), enCoordinates));
}
public static void Examples()
{
Console.WriteLine("-- OS Map reference --");
// Convert to Osgb36 coordinates by creating a new object passing
// in the EastingNorthing object to the constructor.
EastingNorthing eastingNorthing = new EastingNorthing(319267, 175189);
Console.WriteLine("INPUT");
Console.WriteLine($"Easting: {eastingNorthing.Easting}");
Console.WriteLine($"Northing: {eastingNorthing.Northing}");
Osgb36 osgb36EN = new Osgb36(eastingNorthing);
string mapReference = osgb36EN.MapReference;
Console.WriteLine("OUTPUT");
Console.WriteLine($"Map reference: {mapReference}");
Console.WriteLine();
}
public static void Example()
{
Console.WriteLine("-- Obtaining Greater Accuracy --");
LatitudeLongitude latLong = new LatitudeLongitude(51.469886, -3.1636964, 108.05);
Console.WriteLine("INPUT");
Console.WriteLine($"Latitude: {latLong.Latitude}");
Console.WriteLine($"Longitude: {latLong.Longitude}");
Console.WriteLine($"Ellipsoidal Height: {latLong.EllipsoidalHeight}");
Osgb36 bng = GeoUK.OSTN.Transform.Etrs89ToOsgb(latLong);
Console.WriteLine("OUTPUT");
Console.WriteLine($"Map reference: {bng.MapReference}");
Console.WriteLine($"Easting: {bng.Easting}");
Console.WriteLine($"Northing: {bng.Northing}");
Console.WriteLine($"Height: {bng.Height}");
Console.WriteLine();
}
public LatitudeLongitude ConvertEastNorthToLatLong_HigherAccuracySlow(double easting, double northing)
{
Osgb36 accurate = new Osgb36(easting, northing);
return(GeoUK.OSTN.Transform.OsgbToEtrs89(accurate));
}
public void Etrs89ToOsgb_OSTN15_Test()
{
string inputFileName = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "TestDataFiles_OSGM15_OSTN15/OSTN15_OSGM15_TestInput_ETRStoOSGB.txt");
string outputFileName = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "TestDataFiles_OSGM15_OSTN15/OSTN15_OSGM15_TestOutput_ETRStoOSGB.txt");
List <DataPoint> inputData = new List <DataPoint>();
Dictionary <string, DataPoint> outputData = new Dictionary <string, DataPoint>();
using (StreamReader inputFile = new StreamReader(inputFileName))
{
string line;
while ((line = inputFile.ReadLine()) != null)
{
if (string.IsNullOrEmpty(line) || !line.StartsWith("TP"))
{
continue;
}
string[] values = line.Split(',');
DataPoint point = new DataPoint
{
PointID = values[0],
X = double.Parse(values[1]),
Y = double.Parse(values[2]),
Height = double.Parse(values[3])
};
inputData.Add(point);
}
}
using (StreamReader outputFile = new StreamReader(outputFileName))
{
string line;
while ((line = outputFile.ReadLine()) != null)
{
if (string.IsNullOrEmpty(line) || !line.StartsWith("TP"))
{
continue;
}
string[] values = line.Split(',');
DataPoint point = new DataPoint
{
PointID = values[0],
X = double.Parse(values[1]),
Y = double.Parse(values[2]),
Height = double.Parse(values[3])
};
outputData[point.PointID] = point;
}
}
foreach (DataPoint dataPoint in inputData)
{
Osgb36 transformation = Transform.Etrs89ToOsgb(new LatitudeLongitude(dataPoint.X, dataPoint.Y, dataPoint.Height));
// Comparing values with a precision of 3 decimals, as they are given in the output file.
bool latitudesEqual = outputData[dataPoint.PointID].X
.IsApproximatelyEqualTo(transformation.Easting, 0.001);
bool longitudesEqual = outputData[dataPoint.PointID].Y
.IsApproximatelyEqualTo(transformation.Northing, 0.001);
bool heightsEqual = outputData[dataPoint.PointID].Height
.IsApproximatelyEqualTo(transformation.Height, 0.001);
Assert.True(latitudesEqual);
Assert.True(longitudesEqual);
Assert.True(heightsEqual);
}
}
