nsidc.spheres
Class GreatCircle

java.lang.Object
  nsidc.spheres.Sphere
      nsidc.spheres.GreatCircle

Direct Known Subclasses:

GreatCircleArc, SmallCircle

public class GreatCircle

extends Sphere

GreatCircle class - provides services and information relating to a great circle.

A great circle is a circle on a sphere with whose origin is at the center of the sphere. The shortest distance between any two points on a sphere is the great circle distance. Any two points on a sphere uniquely define a single great circle so long as they are not antipodal.

This class assumes a spherical earth.

See Also:

Sphere, SphericalPolygon

Field Summary

double	a Constant in plane equations ax+by+cz=0
Point[]	arc_point Points that define the great circle (arc endpoints).
double	b Constant in plane equations ax+by+cz=0
double	c Constant in plane equations ax+by+cz=0
protected double	const_term Constant for intermediate results.
protected double	denominator Constant for intermediate results.
protected double	firstX Tmp constant for interim results of the intersect calculations
Point	inflection_point Highest point achieved by the great circle.
Point[]	intersect_point Points for any intersections found.
boolean	is_meridian Boolean to track if the arc is on a meridian or not.
protected double	lin_term Constant for intermediate results.
protected double	m Constant for intermediate results.
protected double	n Constant for intermediate results.
protected double	numerator Constant for intermediate results.
protected double	p Constant for intermediate results.
protected double	planar_const Tmp constant for interim results of the intersect calculations
protected double	q Constant for intermediate results.
protected double	rad Tmp constant for interim results of the intersect calculations
protected double	scale Tmp constant for interim results of the intersect calculations
protected double	secondX Tmp constant for interim results of the intersect calculations
protected double	sphere_const Tmp constant for interim results of the intersect calculations
protected double	sqr_term Constant for intermediate results.
protected double	tmp_z Constant for intermediate results.

Fields inherited from class nsidc.spheres.Sphere

radius, Re_km

Constructor Summary

protected	GreatCircle() Empty constructor - do not use.
	GreatCircle(double[] given_lat, double[] given_lon) Sets the points and initializes the great circle.
	GreatCircle(double given_lat0, double given_lon0, double given_lat1, double given_lon1) Sets the points and initializes the great circle.
	GreatCircle(Point start, Point end)

Method Summary

protected void	init() initializes the great circle.
boolean	intersectsGreatCircle(GreatCircle other) Determine if/where this great circle intersects another.
boolean	intersectsLatitude(double latitude) Determine if this great circle intersects a parallel.
boolean	intersectsSmallCircle(SmallCircle small) Determine if/where this great circle intersects a small circle.
protected void	systemLog(java.lang.String msg, int level) Log diagnostic messages
java.lang.String	toString()

Methods inherited from class nsidc.spheres.Sphere

degrees, degrees, getRadius, normalize, normalize, radians, radians, scalarTripleProductTest, setRadius, systemLog

Methods inherited from class java.lang.Object

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

Field Detail

arc_point

public Point[] arc_point

Points that define the great circle (arc endpoints).

intersect_point

public Point[] intersect_point

Points for any intersections found.

inflection_point

public Point inflection_point

Highest point achieved by the great circle.

a

public double a

Constant in plane equations ax+by+cz=0

b

public double b

Constant in plane equations ax+by+cz=0

c

public double c

Constant in plane equations ax+by+cz=0

is_meridian

public boolean is_meridian

Boolean to track if the arc is on a meridian or not.

planar_const

protected double planar_const

Tmp constant for interim results of the intersect calculations

sphere_const

protected double sphere_const

Tmp constant for interim results of the intersect calculations

scale

protected double scale

Tmp constant for interim results of the intersect calculations

rad

protected double rad

Tmp constant for interim results of the intersect calculations

firstX

protected double firstX

Tmp constant for interim results of the intersect calculations

secondX

protected double secondX

Tmp constant for interim results of the intersect calculations

numerator

protected double numerator

Constant for intermediate results.

denominator

protected double denominator

Constant for intermediate results.

m

protected double m

Constant for intermediate results.

n

protected double n

Constant for intermediate results.

p

protected double p

Constant for intermediate results.

q

protected double q

Constant for intermediate results.

sqr_term

protected double sqr_term

Constant for intermediate results.

lin_term

protected double lin_term

Constant for intermediate results.

const_term

protected double const_term

Constant for intermediate results.

tmp_z

protected double tmp_z

Constant for intermediate results.

Constructor Detail

GreatCircle

protected GreatCircle()

Empty constructor - do not use.

GreatCircle

public GreatCircle(double given_lat0,
                   double given_lon0,
                   double given_lat1,
                   double given_lon1)

Sets the points and initializes the great circle.

GreatCircle

public GreatCircle(double[] given_lat,
                   double[] given_lon)

Sets the points and initializes the great circle.

GreatCircle

public GreatCircle(Point start,
                   Point end)

Method Detail

init

protected void init()

initializes the great circle.

intersectsGreatCircle

public boolean intersectsGreatCircle(GreatCircle other)

Determine if/where this great circle intersects another.

The basic strategy is to convert everything to cartesian 3-space first because the math is easier. All the action takes place in cartesian space. If found the intersection points are placed in the intersect_point array.

Returns:

true if the two great circles intersect.
false if the two great circles do not intersect.

See Also:

Scene, SphericalPolygon

intersectsLatitude

public boolean intersectsLatitude(double latitude)

Determine if this great circle intersects a parallel.

The basic strategy is to convert everything to cartesian 3-space first because the math is easier. All the action takes place in cartesian space. If found the intersection points are placed in the intersect_point array.

Parameters:

latitude - The latitude of interest.

Returns:

true if the great circle intersects the parallel.
false if the great circle does not intersect the parallel.

See Also:

LatLonBoundingBox

intersectsSmallCircle

public boolean intersectsSmallCircle(SmallCircle small)

Determine if/where this great circle intersects a small circle.

The basic strategy is to convert everything to cartesian 3-space first because the math is easier. All the action takes place in cartesian space. If found the intersection points are placed in the intersect_point array.

Returns:

true if the two circles intersect.
false if the two circles do not intersect.

See Also:

Scene, SphericalPolygon

systemLog

protected void systemLog(java.lang.String msg,
                         int level)

Description copied from class: Sphere

Log diagnostic messages

Overrides:

systemLog in class Sphere

Parameters:

msg - Message to log.

level - Debug sensitivity.

toString

public java.lang.String toString()