Class KdTree

java.lang.Object
org.locationtech.jts.index.kdtree.KdTree

public class KdTree extends Object
An implementation of a 2-D KD-Tree. KD-trees provide fast range searching on point data.

This implementation supports detecting and snapping points which are closer than a given distance tolerance. If the same point (up to tolerance) is inserted more than once, it is snapped to the existing node. In other words, if a point is inserted which lies within the tolerance of a node already in the index, it is snapped to that node. When a point is snapped to a node then a new node is not created but the count of the existing node is incremented. If more than one node in the tree is within tolerance of an inserted point, the closest and then lowest node is snapped to.

  • Field Details

    • root

      private KdNode root
    • numberOfNodes

      private long numberOfNodes
    • tolerance

      private double tolerance
  • Constructor Details

    • KdTree

      public KdTree()
      Creates a new instance of a KdTree with a snapping tolerance of 0.0. (I.e. distinct points will not be snapped)
    • KdTree

      public KdTree(double tolerance)
      Creates a new instance of a KdTree, specifying a snapping distance tolerance. Points which lie closer than the tolerance to a point already in the tree will be treated as identical to the existing point.
      Parameters:
      tolerance - the tolerance distance for considering two points equal
  • Method Details

    • toCoordinates

      public static Coordinate[] toCoordinates(Collection kdnodes)
      Converts a collection of KdNodes to an array of Coordinates.
      Parameters:
      kdnodes - a collection of nodes
      Returns:
      an array of the coordinates represented by the nodes
    • toCoordinates

      public static Coordinate[] toCoordinates(Collection kdnodes, boolean includeRepeated)
      Converts a collection of KdNodes to an array of Coordinates, specifying whether repeated nodes should be represented by multiple coordinates.
      Parameters:
      kdnodes - a collection of nodes
      includeRepeated - true if repeated nodes should be included multiple times
      Returns:
      an array of the coordinates represented by the nodes
    • isEmpty

      public boolean isEmpty()
      Tests whether the index contains any items.
      Returns:
      true if the index does not contain any items
    • insert

      public KdNode insert(Coordinate p)
      Inserts a new point in the kd-tree, with no data.
      Parameters:
      p - the point to insert
      Returns:
      the kdnode containing the point
    • insert

      public KdNode insert(Coordinate p, Object data)
      Inserts a new point into the kd-tree.
      Parameters:
      p - the point to insert
      data - a data item for the point
      Returns:
      returns a new KdNode if a new point is inserted, else an existing node is returned with its counter incremented. This can be checked by testing returnedNode.getCount() > 1.
    • findBestMatchNode

      private KdNode findBestMatchNode(Coordinate p)
      Finds the node in the tree which is the best match for a point being inserted. The match is made deterministic by returning the lowest of any nodes which lie the same distance from the point. There may be no match if the point is not within the distance tolerance of any existing node.
      Parameters:
      p - the point being inserted
      Returns:
      the best matching node
    • insertExact

      private KdNode insertExact(Coordinate p, Object data)
      Inserts a point known to be beyond the distance tolerance of any existing node. The point is inserted at the bottom of the exact splitting path, so that tree shape is deterministic.
      Parameters:
      p - the point to insert
      data - the data for the point
      Returns:
      the created node
    • queryNode

      private void queryNode(KdNode currentNode, Envelope queryEnv, boolean odd, KdNodeVisitor visitor)
    • query

      public void query(Envelope queryEnv, KdNodeVisitor visitor)
      Performs a range search of the points in the index and visits all nodes found.
      Parameters:
      queryEnv - the range rectangle to query
      visitor - a visitor to visit all nodes found by the search
    • query

      public List query(Envelope queryEnv)
      Performs a range search of the points in the index.
      Parameters:
      queryEnv - the range rectangle to query
      Returns:
      a list of the KdNodes found
    • query

      public void query(Envelope queryEnv, List result)
      Performs a range search of the points in the index.
      Parameters:
      queryEnv - the range rectangle to query
      result - a list to accumulate the result nodes into