com.vividsolutions.jts.index.strtree

Class STRtree

  • All Implemented Interfaces:
    SpatialIndex, Serializable 

    public class STRtree
extends AbstractSTRtree
implements SpatialIndex, Serializable
    A query-only R-tree created using the Sort-Tile-Recursive (STR) algorithm. For two-dimensional spatial data.

    The STR packed R-tree is simple to implement and maximizes space utilization; that is, as many leaves as possible are filled to capacity. Overlap between nodes is far less than in a basic R-tree. However, once the tree has been built (explicitly or on the first call to #query), items may not be added or removed.

    Described in: P. Rigaux, Michel Scholl and Agnes Voisard. Spatial Databases With Application To GIS. Morgan Kaufmann, San Francisco, 2002.

    See Also:
    Serialized Form

    • Constructor Detail

      • STRtree

        public STRtree()
        Constructs an STRtree with the default node capacity.

      • STRtree

        public STRtree(int nodeCapacity)
        Constructs an STRtree with the given maximum number of child nodes that a node may have.

        The minimum recommended capacity setting is 4.

    • Method Detail

      • createParentBoundables

        protected List createParentBoundables(List childBoundables,
                                      int newLevel)
        Creates the parent level for the given child level. First, orders the items by the x-values of the midpoints, and groups them into vertical slices. For each slice, orders the items by the y-values of the midpoints, and group them into runs of size M (the node capacity). For each run, creates a new (parent) node.

      • createParentBoundablesFromVerticalSlice

        protected List createParentBoundablesFromVerticalSlice(List childBoundables,
                                                       int newLevel)

      • verticalSlices

        protected List[] verticalSlices(List childBoundables,
                                int sliceCount)
        Parameters:
        childBoundables - Must be sorted by the x-value of the envelope midpoints

      • insert

        public void insert(Envelope itemEnv,
                   Object item)
        Inserts an item having the given bounds into the tree.

      • query

        public List query(Envelope searchEnv)
        Returns items whose bounds intersect the given envelope.
        Specified by:
        query in interface  SpatialIndex
        Parameters:
        searchEnv - the envelope to query for
        Returns:
        a list of the items found by the query

      • query

        public void query(Envelope searchEnv,
                  ItemVisitor visitor)
        Returns items whose bounds intersect the given envelope.
        Specified by:
        query in interface  SpatialIndex
        Parameters:
        searchEnv - the envelope to query for
        visitor - a visitor object to apply to the items found

      • remove

        public boolean remove(Envelope itemEnv,
                      Object item)
        Removes a single item from the tree.
        Specified by:
        remove in interface  SpatialIndex
        Parameters:
        itemEnv - the Envelope of the item to remove
        item - the item to remove
        Returns:
        true if the item was found

      • size

        public int size()
        Returns the number of items in the tree.
        Overrides:
        size in class  AbstractSTRtree
        Returns:
        the number of items in the tree

      • depth

        public int depth()
        Returns the number of items in the tree.
        Overrides:
        depth in class  AbstractSTRtree
        Returns:
        the number of items in the tree

      • getComparator

        protected Comparator getComparator()

      • nearestNeighbour

        public Object[] nearestNeighbour(ItemDistance itemDist)
        Finds the two nearest items in the tree, using ItemDistance as the distance metric. A Branch-and-Bound tree traversal algorithm is used to provide an efficient search.
        Parameters:
        itemDist - a distance metric applicable to the items in this tree
        Returns:
        the pair of the nearest items

      • nearestNeighbour

        public Object nearestNeighbour(Envelope env,
                               Object item,
                               ItemDistance itemDist)
        Finds the item in this tree which is nearest to the given Object, using ItemDistance as the distance metric. A Branch-and-Bound tree traversal algorithm is used to provide an efficient search.

        The query object does not have to be contained in the tree, but it does have to be compatible with the itemDist distance metric.

        Parameters:
        env - the envelope of the query item
        item - the item to find the nearest neighbour of
        itemDist - a distance metric applicable to the items in this tree and the query item
        Returns:
        the nearest item in this tree

      • nearestNeighbour

        public Object[] nearestNeighbour(STRtree tree,
                                 ItemDistance itemDist)
        Finds the two nearest items from this tree and another tree, using ItemDistance as the distance metric. A Branch-and-Bound tree traversal algorithm is used to provide an efficient search. The result value is a pair of items, the first from this tree and the second from the argument tree.
        Parameters:
        tree - another tree
        itemDist - a distance metric applicable to the items in the trees
        Returns:
        the pair of the nearest items, one from each tree