oracle.spatial.geometry

Class UnitSphere

java.lang.Object

oracle.spatial.geometry.JPoint3DD

oracle.spatial.geometry.UnitSphere

public final class UnitSphere
extends JPoint3DD

Immutable 3D representation of a point on a sphere with conversions to and from long/lat. The vector is always normalized (length 1) unless it is zero.

Constructor Summary

Constructors

Constructor and Description
UnitSphere(double x, double y) Create this UnitSphere equivalent to the given long/lat point.
UnitSphere(double x, double y, double z) Creates a normalized (x, y, z) (unless they are all zero, in which case creates (0, 0, 0)).
UnitSphere(JPoint2DD pt2D) Create this UnitSphere equivalent to the given long/lat point.
UnitSphere(JPoint3DD pt) Creates a 3D vector on the unit sphere as a normalized copy of the passed 3D point.

Method Summary

Modifier and Type	Method and Description
JPoint2DD	computeLongLat() Compute and return the long/lat equivalent to this unit-sphere point.
static double	distancePtLineRadians(UnitSphere pt, UnitSphere a, UnitSphere b) Return the distance on the unit sphere (an angle) between a point and a great-circle line segment.
static double	distanceRadians(UnitSphere a, UnitSphere b) Distance on the unit sphere between two points.
boolean	equals(java.lang.Object obj) Equality is based on the (x, y, z) values.
JPoint2DD	getLongLat() Retuns original long/lat equivalent of this UnitSphere, or if none, computes one.
static JPoint3DD	greatCircle(UnitSphere a, UnitSphere b) Compute the great circle through two points, and return it as the vector perpindicular to the plane through the two points and the center of the earth.
int	hashCode()
static UnitSphere	intersect(JPoint3DD GCa, JPoint3DD GCb) Return the intersection of two great-circles.
static UnitSphere	intersect(UnitSphere a1, UnitSphere a2, UnitSphere b1, UnitSphere b2) Return an intersection of two great-circle segments, or null if none.
static UnitSphere	nearestPtLine(UnitSphere pt, UnitSphere a, UnitSphere b) Return a point on great-circle segment ab that is closest to pt.
java.lang.String	toString()

Methods inherited from class oracle.spatial.geometry.JPoint3DD

cross, dot, getX, getY, getZ, isZero, length

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

UnitSphere

public UnitSphere(double x,
                  double y)

Create this UnitSphere equivalent to the given long/lat point.

Parameters:

x - longitude in degrees

y - latitude in degrees

UnitSphere

public UnitSphere(JPoint2DD pt2D)

Create this UnitSphere equivalent to the given long/lat point.

Parameters:

pt2D - (Longitude, latitude) in degrees.

UnitSphere

public UnitSphere(double x,
                  double y,
                  double z)

Creates a normalized (x, y, z) (unless they are all zero, in which case creates (0, 0, 0)).

Parameters:

x -

y -

z -

UnitSphere

public UnitSphere(JPoint3DD pt)

Creates a 3D vector on the unit sphere as a normalized copy of the passed 3D point.

Parameters:

pt -

Method Detail

distanceRadians

public static double distanceRadians(UnitSphere a,
                                     UnitSphere b)

Distance on the unit sphere between two points. Result is just the angle between the two points (vectors); multiply by the radius of the earth to get the distance in the units you want.

Parameters:

a -

b -

Returns:

angle in radians

greatCircle

public static JPoint3DD greatCircle(UnitSphere a,
                                    UnitSphere b)

Compute the great circle through two points, and return it as the vector perpindicular to the plane through the two points and the center of the earth. Note that vector is not normalized.

Parameters:

a -

b -

Returns:

perpindicular to plane through a, b, center-of-earth

intersect

public static UnitSphere intersect(JPoint3DD GCa,
                                   JPoint3DD GCb)

Return the intersection of two great-circles.

Parameters:

GCa - a vector perpindicular to one great-circle cut through the earth

GCb - a vector perpindicular to the other great circle.

Returns:

vector pointing along the line of intersection (Or zero-length, if coincident)

intersect

public static UnitSphere intersect(UnitSphere a1,
                                   UnitSphere a2,
                                   UnitSphere b1,
                                   UnitSphere b2)

Return an intersection of two great-circle segments, or null if none. Note that a great-circle that is larger than half the earth could have two intersections, but since we always interpret great-circle segments to be the short way around, the only way that could happen is via two great-circle segments between antipods, and we have no way of representing such great-circles distinctly anyway.

Does not reliably find endpoint-on-segment intersections; test for those separately.

Parameters:

a1 - (a1, a2) is the first segment

a2 -

b1 - (b1, b2) is the second segment

b2 -

Returns:

intersection point, or null

distancePtLineRadians

public static double distancePtLineRadians(UnitSphere pt,
                                           UnitSphere a,
                                           UnitSphere b)

Return the distance on the unit sphere (an angle) between a point and a great-circle line segment.

Parameters:

pt -

a -

b -

Returns:

distance as an angle in radians

nearestPtLine

public static UnitSphere nearestPtLine(UnitSphere pt,
                                       UnitSphere a,
                                       UnitSphere b)

Return a point on great-circle segment ab that is closest to pt.

Parameters:

pt -

a -

b -

Returns:

closest point on segment

getLongLat

public JPoint2DD getLongLat()

Retuns original long/lat equivalent of this UnitSphere, or if none, computes one.

Returns:

copy of the long/lat equivalent of this UnitSphere.

computeLongLat

public JPoint2DD computeLongLat()

Compute and return the long/lat equivalent to this unit-sphere point. Compare to getLongLat(). Does not use original value.

Returns:

computed longitude/latitude equivalent

toString

public java.lang.String toString()

Overrides:

toString in class JPoint3DD

equals

public boolean equals(java.lang.Object obj)

Equality is based on the (x, y, z) values. The origLongLat field is not included.

Overrides:

equals in class JPoint3DD

Parameters:

obj -

Returns:

hashCode

public int hashCode()

Overrides:

hashCode in class JPoint3DD