Package ca.spatial.table

Class ShapeSpatialIndex

java.lang.Object

ca.spatial.table.ShapeSpatialIndex

All Implemented Interfaces:

SpatialIndex

public class ShapeSpatialIndex
extends Object
implements SpatialIndex

Encapsulate access to a shapefile spatial index. This class performs optimistic indexing. The set of records that are returned will include at least the selection. The records will be tested using a fast but approximate criteria, and some boundary records may be included. Routines that use this class should perform additional refinement on this list.

Constructor Summary

Constructors

Constructor	Description
ShapeSpatialIndex(ShapeStore grs, boolean universe)	Create a spatial index from the features in an existing data set
ShapeSpatialIndex(String fileName, String indexName, Extent2D parentExtent)	Read an existing spatial index

Method Summary

Modifier and Type	Method	Description
void	close()
void	dump(PrintStream out)	Print the index to the output stream
void	exportToShapefile(String name)	Export the indexing structure to a shapefile.
int	getDepth()	The depth of partitions in this index
Extent2D	getExtent()	The extent of the index.
int	getRecordCount()	Get the number of feature in this index
BitSet	getSelection(Extent2D e)	Retrieve a spatial selection.
BitSet	getSelection(Extent2D e, int offset)	Retrieve a spatial selection.
void	saveIndex(String dataName, String indexName, int magic1, int magic2)	Save this index to permanent files.
String	toString()

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Details

ShapeSpatialIndex

public ShapeSpatialIndex(ShapeStore grs,
 boolean universe)

Create a spatial index from the features in an existing data set

Parameters:

grs - The reference to the spatial data set

universe - Indicates if an additional universe polygon index record should be added. This is required for building indexes on polygon coverage data sets. It is never required for shapefiles.

ShapeSpatialIndex

public ShapeSpatialIndex(String fileName,
 String indexName,
 Extent2D parentExtent)
                  throws IOException

Read an existing spatial index

Parameters:

fileName - The name of the file containing the spatial index records. For shapefiles this is the sbn file.

indexName - The name of the file that indexes the spatial index records. For shapefiles this is the sbx file.

Throws:

IOException

Method Details

close

public void close()

exportToShapefile

public void exportToShapefile(String name)
                       throws IOException

Export the indexing structure to a shapefile. This is diagnostic aid to help troubleshoot problems with spatial index encoding and decoding.

Parameters:

name - The nameof the shapefile to create. The file will contain polygons for each indexed feature showing their coverage in the index.

Throws:

IOException - Will throw a IOException if there is trouble while creating the shapefile.

getExtent

public Extent2D getExtent()

The extent of the index. Note that this is the bounding box of all features in single precision floating point

Specified by:

getExtent in interface SpatialIndex

getDepth

public int getDepth()

The depth of partitions in this index

getRecordCount

public int getRecordCount()

Get the number of feature in this index

getSelection

public BitSet getSelection(Extent2D e)

Retrieve a spatial selection. The selection is fast and optimistic, including records that are likely to be in the selection. The returned set may include additional boudary records and so should be checked using a more refined test to see if the records actually match.

This method is equivalent to

 getselection(e, 0);
 

Specified by:

getSelection in interface SpatialIndex

Parameters:

e - The rectangle that represents the spatial query

getSelection

public BitSet getSelection(Extent2D e,
 int offset)

Retrieve a spatial selection. The selection is fast and optimistic, including records that are likely to be in the selection. The returned set may include additional boudary records and so should be checked using a more refined test to see if the records actually match.

Specified by:

getSelection in interface SpatialIndex

Parameters:

e - The rectangle that represents the spatial query

offset - This parameter indicates how records in the index relate to records in the data set. Most data sets have a one-to-one relationship and this parameter should be zero. Polygon coverages have a universe polygon which is ignored, so in this case specify an offset of 1.

dump

public void dump(PrintStream out)

Print the index to the output stream

Specified by:

dump in interface SpatialIndex

toString

public String toString()

Overrides:

toString in class Object

saveIndex

public void saveIndex(String dataName,
 String indexName,
 int magic1,
 int magic2)
               throws Exception

Save this index to permanent files. The index is saved in two parts:

• The index data, containing the search tree
• The index to the index, containing direct access record pointers.

In addition the index must contain special magic numbers to identify the type of spatial index. Known index names and magic numbers are:

Spatial file magic numbers

Data set type	Data name	Index name	Magic1	Magic2
Any shapefile	filename.sbn	filename.sbx	9994	-400
Point coverage	coverage/xbn.adf	coverage/xbx.adf	9994	-46
Line coverage	coverage/abn.adf	coverage/abx.adf	9994	-47
Polygon coverage	coverage/pbn.adf	coverage/pbx.adf	9994	-48

Parameters:

dataName - The name of the file to store the index data in to

indexName - The name of the file to store the direct access pointers in to.

magic1 - The first magic number

magic2 - The second magic number

Throws:

Exception