/// <summary>
/// Returns the coordinate at an offset of the lineString
/// </summary>
/// <param name="lineString"></param>
/// <param name="distance"></param>
/// <returns></returns>
/// <remarks>
/// Be aware that this function can suffer from double precision issue, like: 100.0*0.55 evaluates to 55.000000000000007
/// </remarks>
public static Coordinate LineStringCoordinate(ILineString lineString, double distance)
{
double partialDistance = 0;
Coordinate[] coordinates = lineString.Coordinates;
for (int i = 1; i < coordinates.Length; i++)
{
Coordinate c1 = coordinates[i - 1];
Coordinate c2 = coordinates[i];
double segmentDistance = Distance(c1.X, c1.Y, c2.X, c2.Y);
if ((partialDistance + segmentDistance) > distance)
{
double factor = (distance - partialDistance) / (segmentDistance);
return(GeometryFactoryEx.CreateCoordinate(
coordinates[i - 1].X + factor * (coordinates[i].X - coordinates[i - 1].X),
coordinates[i - 1].Y + factor * (coordinates[i].Y - coordinates[i - 1].Y)));
}
partialDistance += segmentDistance;
}
return((Coordinate)lineString.Coordinates[lineString.Coordinates.Length - 1].Clone());
}
static public Coordinate NearestPointAtSegment(double Ax, double Ay, double Bx, double By,
double cx, double cy)
{
// if (AB . BC) > 0)
if (Dot(Ax, Ay, Bx, By, cx, cy) > 0)
{
return(GeometryFactoryEx.CreateCoordinate(Bx, By));
}
// else if ((BA . AC) > 0)
else if (Dot(Bx, By, Ax, Ay, cx, cy) > 0)
{
return(GeometryFactoryEx.CreateCoordinate(Ax, Ay));
}
else
// both dot products < 0 -> point between A and B
{
double AC = Distance(Ax, Ay, cx, cy);
double BC = Distance(Bx, By, cx, cy);
return(GeometryFactoryEx.CreateCoordinate(Ax + ((AC) / (AC + BC)) * (Bx - Ax),
Ay + ((AC) / (AC + BC)) * (By - Ay)));
}
}
