convert latitude/longitude (4326) to cartesian/ecef (4978)

convert_4326_4978.txt

Two methods to get from 4326 (longitude, latitude) to 4978 (cartesian - ecef). TLDR; use DotSpatial.Positioning when possible (because much faster).


1] using DotSpatial.Positioning (fast):

```
private static System.Numerics.Vector3 ToCartesian(double lat, double lon, double alt)
{
    var pos3d = new Position3D(new Distance(alt, DistanceUnit.Meters), new Latitude(lat), new Longitude(lon));
    var res1 = pos3d.ToCartesianPoint();
    return new System.Numerics.Vector3((float)res1.X.Value, (float)res1.Y.Value, (float)res1.Z.Value);
}
```

and back ... 

```
static (double x, double y, double z) FromVector3(Vector3 vec)
{
    var cartesianPoint = new CartesianPoint(new Distance(vec.X, DistanceUnit.Meters), new Distance(vec.Y, DistanceUnit.Meters), new Distance(vec.Z, DistanceUnit.Meters));
    var pos3 = cartesianPoint.ToPosition3D();
    return ((double)pos3.Longitude, (double)pos3.Latitude, pos3.Altitude.Value);
}
```

2] using gdal (slow): 

call using GetCartesian(p, 4326, 4978)
```
public static System.Numerics.Vector3 GetCartesian (point, int from, int to)
{
    var src = new SpatialReference("");
    src.ImportFromEPSG(from);
    var dst = new SpatialReference("");
    dst.ImportFromEPSG(to);
    var ct = new CoordinateTransformation(src, dst);
    double[] p = new double[3];
    p[0] = point.Coordinates.Longitude;
    p[1] = point.Coordinates.Latitude;
    p[2] = (double)point.Coordinates.Altitude;
    ct.TransformPoint(p);

    return new System.Numerics.Vector3((float)p[0], (float)p[1], (float)p[2]);
}
```