Package org.apache.lucene.geo

Class GeoEncodingUtils

java.lang.Object

org.apache.lucene.geo.GeoEncodingUtils

public final class GeoEncodingUtils
extends Object

reusable geopoint encoding methods

WARNING: This API is experimental and might change in incompatible ways in the next release.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	GeoEncodingUtils.Component2DPredicate	A predicate that checks whether a given point is within a component2D geometry.
static class	GeoEncodingUtils.DistancePredicate	A predicate that checks whether a given point is within a distance of another point.

Field Summary

Fields

Modifier and Type	Field	Description
static short	BITS	number of bits used for quantizing latitude and longitude values
static int	MAX_LON_ENCODED
static int	MIN_LON_ENCODED

Method Summary

Modifier and Type	Method	Description
static GeoEncodingUtils.Component2DPredicate	createComponentPredicate(Component2D tree)	Create a predicate that checks whether points are within a geometry.
static GeoEncodingUtils.DistancePredicate	createDistancePredicate(double lat, double lon, double radiusMeters)	Create a predicate that checks whether points are within a distance of a given point.
static double	decodeLatitude(byte[] src, int offset)	Turns quantized value from byte array back into a double.
static double	decodeLatitude(int encoded)	Turns quantized value from encodeLatitude(double) back into a double.
static double	decodeLongitude(byte[] src, int offset)	Turns quantized value from byte array back into a double.
static double	decodeLongitude(int encoded)	Turns quantized value from encodeLongitude(double) back into a double.
static int	encodeLatitude(double latitude)	Quantizes double (64 bit) latitude into 32 bits (rounding down: in the direction of -90)
static int	encodeLatitudeCeil(double latitude)	Quantizes double (64 bit) latitude into 32 bits (rounding up: in the direction of +90)
static int	encodeLongitude(double longitude)	Quantizes double (64 bit) longitude into 32 bits (rounding down: in the direction of -180)
static int	encodeLongitudeCeil(double longitude)	Quantizes double (64 bit) longitude into 32 bits (rounding up: in the direction of +180)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

BITS

public static final short BITS

number of bits used for quantizing latitude and longitude values

See Also:

Constant Field Values

MIN_LON_ENCODED

public static final int MIN_LON_ENCODED

MAX_LON_ENCODED

public static final int MAX_LON_ENCODED

Method Detail

encodeLatitude

public static int encodeLatitude(double latitude)

Quantizes double (64 bit) latitude into 32 bits (rounding down: in the direction of -90)

Parameters:

latitude - latitude value: must be within standard +/-90 coordinate bounds.

Returns:

encoded value as a 32-bit int

Throws:

IllegalArgumentException - if latitude is out of bounds

encodeLatitudeCeil

public static int encodeLatitudeCeil(double latitude)

Quantizes double (64 bit) latitude into 32 bits (rounding up: in the direction of +90)

Parameters:

latitude - latitude value: must be within standard +/-90 coordinate bounds.

Returns:

encoded value as a 32-bit int

Throws:

IllegalArgumentException - if latitude is out of bounds

encodeLongitude

public static int encodeLongitude(double longitude)

Quantizes double (64 bit) longitude into 32 bits (rounding down: in the direction of -180)

Parameters:

longitude - longitude value: must be within standard +/-180 coordinate bounds.

Returns:

encoded value as a 32-bit int

Throws:

IllegalArgumentException - if longitude is out of bounds

encodeLongitudeCeil

public static int encodeLongitudeCeil(double longitude)

Quantizes double (64 bit) longitude into 32 bits (rounding up: in the direction of +180)

Parameters:

longitude - longitude value: must be within standard +/-180 coordinate bounds.

Returns:

encoded value as a 32-bit int

Throws:

IllegalArgumentException - if longitude is out of bounds

decodeLatitude

public static double decodeLatitude(int encoded)

Turns quantized value from encodeLatitude(double) back into a double.

Parameters:

encoded - encoded value: 32-bit quantized value.

Returns:

decoded latitude value.

decodeLatitude

public static double decodeLatitude(byte[] src,
                                    int offset)

Turns quantized value from byte array back into a double.

Parameters:

src - byte array containing 4 bytes to decode at offset

offset - offset into src to decode from.

Returns:

decoded latitude value.

decodeLongitude

public static double decodeLongitude(int encoded)

Turns quantized value from encodeLongitude(double) back into a double.

Parameters:

encoded - encoded value: 32-bit quantized value.

Returns:

decoded longitude value.

decodeLongitude

public static double decodeLongitude(byte[] src,
                                     int offset)

Turns quantized value from byte array back into a double.

Parameters:

src - byte array containing 4 bytes to decode at offset

offset - offset into src to decode from.

Returns:

decoded longitude value.

createDistancePredicate

public static GeoEncodingUtils.DistancePredicate createDistancePredicate(double lat,
                                                                         double lon,
                                                                         double radiusMeters)

Create a predicate that checks whether points are within a distance of a given point. It works by computing the bounding box around the circle that is defined by the given points/distance and splitting it into between 1024 and 4096 smaller boxes (4096*0.75^2=2304 on average). Then for each sub box, it computes the relation between this box and the distance query. Finally at search time, it first computes the sub box that the point belongs to, most of the time, no distance computation will need to be performed since all points from the sub box will either be in or out of the circle.

NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

createComponentPredicate

public static GeoEncodingUtils.Component2DPredicate createComponentPredicate(Component2D tree)

Create a predicate that checks whether points are within a geometry. It works the same way as createDistancePredicate(double, double, double).

NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.