Class Quadtree
- All Implemented Interfaces:
Serializable
,SpatialIndex
Geometry
s can be indexed by using their
Envelope
s.
Any type of Object can also be indexed as
long as it has an extent that can be represented by an Envelope
.
This Quadtree index provides a primary filter for range rectangle queries. The various query methods return a list of all items which may intersect the query rectangle. Note that it may thus return items which do not in fact intersect the query rectangle. A secondary filter is required to test for actual intersection between the query rectangle and the envelope of each candidate item. The secondary filter may be performed explicitly, or it may be provided implicitly by subsequent operations executed on the items (for instance, if the index query is followed by computing a spatial predicate between the query geometry and tree items, the envelope intersection check is performed automatically.
This implementation does not require specifying the extent of the inserted items beforehand. It will automatically expand to accommodate any extent of dataset.
This data structure is also known as an MX-CIF quadtree following the terminology of Samet and others.
- Version:
- 1.7
- See Also:
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionint
depth()
Returns the number of levels in the tree.static Envelope
ensureExtent
(Envelope itemEnv, double minExtent) Ensure that the envelope for the inserted item has non-zero extents.void
Adds a spatial item with an extent specified by the givenEnvelope
to the indexboolean
isEmpty()
Tests whether the index contains any items.Queries the tree and returns items which may lie in the given search envelope.void
query
(Envelope searchEnv, ItemVisitor visitor) Queries the tree and visits items which may lie in the given search envelope.queryAll()
Return a list of all items in the Quadtreeboolean
Removes a single item from the tree.int
size()
Returns the number of items in the tree.
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Constructor Details
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Quadtree
public Quadtree()Constructs a Quadtree with zero items.
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Method Details
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ensureExtent
Ensure that the envelope for the inserted item has non-zero extents. Use the current minExtent to pad the envelope, if necessary -
depth
public int depth()Returns the number of levels in the tree. -
isEmpty
public boolean isEmpty()Tests whether the index contains any items.- Returns:
- true if the index does not contain any items
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size
public int size()Returns the number of items in the tree.- Returns:
- the number of items in the tree
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insert
Description copied from interface:SpatialIndex
Adds a spatial item with an extent specified by the givenEnvelope
to the index- Specified by:
insert
in interfaceSpatialIndex
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remove
Removes a single item from the tree.- Specified by:
remove
in interfaceSpatialIndex
- Parameters:
itemEnv
- the Envelope of the item to be removeditem
- the item to remove- Returns:
true
if the item was found (and thus removed)
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query
Queries the tree and returns items which may lie in the given search envelope. Precisely, the items that are returned are all items in the tree whose envelope may intersect the search Envelope. Note that some items with non-intersecting envelopes may be returned as well; the client is responsible for filtering these out. In most situations there will be many items in the tree which do not intersect the search envelope and which are not returned - thus providing improved performance over a simple linear scan.- Specified by:
query
in interfaceSpatialIndex
- Parameters:
searchEnv
- the envelope of the desired query area.- Returns:
- a List of items which may intersect the search envelope
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query
Queries the tree and visits items which may lie in the given search envelope. Precisely, the items that are visited are all items in the tree whose envelope may intersect the search Envelope. Note that some items with non-intersecting envelopes may be visited as well; the client is responsible for filtering these out. In most situations there will be many items in the tree which do not intersect the search envelope and which are not visited - thus providing improved performance over a simple linear scan.- Specified by:
query
in interfaceSpatialIndex
- Parameters:
searchEnv
- the envelope of the desired query area.visitor
- a visitor object which is passed the visited items
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queryAll
Return a list of all items in the Quadtree
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