com.vividsolutions.jts.linearref

Class LengthIndexedLine


  • public class LengthIndexedLine
extends Object
    Supports linear referencing along a linear Geometry using the length along the line as the index. Negative length values are taken as measured in the reverse direction from the end of the geometry. Out-of-range index values are handled by clamping them to the valid range of values. Non-simple lines (i.e. which loop back to cross or touch themselves) are supported.

    • Constructor Summary

      Constructors

      Constructor and Description
      LengthIndexedLine(Geometry linearGeom)
      Constructs an object which allows a linear Geometry to be linearly referenced using length as an index.

    • Method Summary

      Modifier and Type Method and Description
      double clampIndex(double index)
      Computes a valid index for this line by clamping the given index to the valid range of index values
      Geometry extractLine(double startIndex, double endIndex)
      Computes the LineString for the interval on the line between the given indices.
      Coordinate extractPoint(double index)
      Computes the Coordinate for the point on the line at the given index.
      Coordinate extractPoint(double index, double offsetDistance)
      Computes the Coordinate for the point on the line at the given index, offset by the given distance.
      double getEndIndex()
      Returns the index of the end of the line
      double getStartIndex()
      Returns the index of the start of the line
      double indexOf(Coordinate pt)
      Computes the minimum index for a point on the line.
      double indexOfAfter(Coordinate pt, double minIndex)
      Finds the index for a point on the line which is greater than the given index.
      double[] indicesOf(Geometry subLine)
      Computes the indices for a subline of the line.
      boolean isValidIndex(double index)
      Tests whether an index is in the valid index range for the line.
      double project(Coordinate pt)
      Computes the index for the closest point on the line to the given point.

    • Constructor Detail

      • LengthIndexedLine

        public LengthIndexedLine(Geometry linearGeom)
        Constructs an object which allows a linear Geometry to be linearly referenced using length as an index.
        Parameters:
        linearGeom - the linear geometry to reference along

    • Method Detail

      • extractPoint

        public Coordinate extractPoint(double index)
        Computes the Coordinate for the point on the line at the given index. If the index is out of range the first or last point on the line will be returned. The Z-ordinate of the computed point will be interpolated from the Z-ordinates of the line segment containing it, if they exist.
        Parameters:
        index - the index of the desired point
        Returns:
        the Coordinate at the given index

      • extractPoint

        public Coordinate extractPoint(double index,
                               double offsetDistance)
        Computes the Coordinate for the point on the line at the given index, offset by the given distance. If the index is out of range the first or last point on the line will be returned. The computed point is offset to the left of the line if the offset distance is positive, to the right if negative. The Z-ordinate of the computed point will be interpolated from the Z-ordinates of the line segment containing it, if they exist.
        Parameters:
        index - the index of the desired point
        offsetDistance - the distance the point is offset from the segment (positive is to the left, negative is to the right)
        Returns:
        the Coordinate at the given index

      • extractLine

        public Geometry extractLine(double startIndex,
                            double endIndex)
        Computes the LineString for the interval on the line between the given indices. If the endIndex lies before the startIndex, the computed geometry is reversed.
        Parameters:
        startIndex - the index of the start of the interval
        endIndex - the index of the end of the interval
        Returns:
        the linear interval between the indices

      • indexOf

        public double indexOf(Coordinate pt)
        Computes the minimum index for a point on the line. If the line is not simple (i.e. loops back on itself) a single point may have more than one possible index. In this case, the smallest index is returned. The supplied point does not necessarily have to lie precisely on the line, but if it is far from the line the accuracy and performance of this function is not guaranteed. Use project(com.vividsolutions.jts.geom.Coordinate) to compute a guaranteed result for points which may be far from the line.
        Parameters:
        pt - a point on the line
        Returns:
        the minimum index of the point
        See Also:
        project(Coordinate)

      • indexOfAfter

        public double indexOfAfter(Coordinate pt,
                           double minIndex)
        Finds the index for a point on the line which is greater than the given index. If no such index exists, returns minIndex. This method can be used to determine all indexes for a point which occurs more than once on a non-simple line. It can also be used to disambiguate cases where the given point lies slightly off the line and is equidistant from two different points on the line. The supplied point does not necessarily have to lie precisely on the line, but if it is far from the line the accuracy and performance of this function is not guaranteed. Use project(com.vividsolutions.jts.geom.Coordinate) to compute a guaranteed result for points which may be far from the line.
        Parameters:
        pt - a point on the line
        minIndex - the value the returned index must be greater than
        Returns:
        the index of the point greater than the given minimum index
        See Also:
        project(Coordinate)

      • indicesOf

        public double[] indicesOf(Geometry subLine)
        Computes the indices for a subline of the line. (The subline must conform to the line; that is, all vertices in the subline (except possibly the first and last) must be vertices of the line and occcur in the same order).
        Parameters:
        subLine - a subLine of the line
        Returns:
        a pair of indices for the start and end of the subline.

      • project

        public double project(Coordinate pt)
        Computes the index for the closest point on the line to the given point. If more than one point has the closest distance the first one along the line is returned. (The point does not necessarily have to lie precisely on the line.)
        Parameters:
        pt - a point on the line
        Returns:
        the index of the point

      • getStartIndex

        public double getStartIndex()
        Returns the index of the start of the line
        Returns:
        the start index

      • getEndIndex

        public double getEndIndex()
        Returns the index of the end of the line
        Returns:
        the end index

      • isValidIndex

        public boolean isValidIndex(double index)
        Tests whether an index is in the valid index range for the line.
        Parameters:
        index - the index to test
        Returns:
        true if the index is in the valid range

      • clampIndex

        public double clampIndex(double index)
        Computes a valid index for this line by clamping the given index to the valid range of index values
        Returns:
        a valid index value