nsidc.spheres
Class GreatCircleArc

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

public class GreatCircleArc

extends GreatCircle

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

A great circle arc is a piece of a great circle. The sides of spherical polygons are great circle arcs so we need this class to compare spherical polygons to other areas on the sphere.

This class assumes a spherical earth.

See Also:

Sphere, SphericalPolygon, GreatCircle

Field Summary

double	arc_length_deg Length of the arc in degrees.
double	arc_length_rad Length of the arc in radians.
boolean	crosses_pole Boolean to track if the arc crosses a pole or not.
LatRange	lat_range Latitude range of the arc.
LonRange	lon_range Longitude range of the arc.

Fields inherited from class nsidc.spheres.GreatCircle

a, arc_point, b, c, const_term, inflection_point, intersect_point, is_meridian, lin_term, m, n, p, q, sqr_term, tmp_z

Fields inherited from class nsidc.spheres.Sphere

radius, Re_km

Constructor Summary

GreatCircleArc(double[] given_lat, double[] given_lon)
Sets the endpoints and initializes the arc.

GreatCircleArc(double given_lat0, double given_lon0, double given_lat1, double given_lon1)
Sets the endpoints and initializes the arc.

GreatCircleArc(Point start, Point end)
Sets the endpoints and initializes the arc.

Method Summary

Point	center() Find the center of the arc
Point[]	densify(double distance_rad) Densify the arc
protected void	init() initializes the arc.
boolean	intersectsArc(GreatCircleArc other) Determine if this arc intersects another.
boolean	intersectsLatSeg(double seg_lat, double min_lon, double max_lon) Determine if this arc intersects a segment of a parallel.
boolean	intersectsSCArc(SmallCircleArc small_circle_arc) Determine if this arc intersects a small circle arc.
protected void	systemLog(java.lang.String msg, int level) Log diagnostic messages

Methods inherited from class nsidc.spheres.GreatCircle

intersectsGreatCircle, intersectsLatitude, intersectsSmallCircle, 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

crosses_pole

public boolean crosses_pole

Boolean to track if the arc crosses a pole or not.

lon_range

public LonRange lon_range

Longitude range of the arc.

lat_range

public LatRange lat_range

Latitude range of the arc.

arc_length_rad

public double arc_length_rad

Length of the arc in radians.

arc_length_deg

public double arc_length_deg

Length of the arc in degrees.

Constructor Detail

GreatCircleArc

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

Sets the endpoints and initializes the arc.

GreatCircleArc

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

Sets the endpoints and initializes the arc.

GreatCircleArc

public GreatCircleArc(Point start,
                      Point end)

Sets the endpoints and initializes the arc.

Method Detail

init

protected void init()

initializes the arc.

Overrides:

init in class GreatCircle

intersectsArc

public boolean intersectsArc(GreatCircleArc other)

Determine if this arc 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. Then we convert back to spherical and see what's what.

Returns:

true if the two arcs intersect.
false if the two arcs do not instersect.

See Also:

Scene

intersectsLatSeg

public boolean intersectsLatSeg(double seg_lat,
                                double min_lon,
                                double max_lon)

Determine if this arc intersects a segment of 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. Then we convert back to spherical and see what's what.

Parameters:

seg_lat - The latitude of the segment.

min_lon - The minimun longitude of the segment.

max_lon - The maximum longitude of the segment.

Returns:

true if the two arcs intersect.
false if the two arcs do not instersect.

See Also:

LatLonBoundingBox

intersectsSCArc

public boolean intersectsSCArc(SmallCircleArc small_circle_arc)

Determine if this arc intersects a small circle arc.

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. Then we convert back to spherical and see what's what. This method is not actually implemented yet and always returns false.

Parameters:

small_circle_arc - The small circle arc of interest.

Returns:

true if the two arcs intersect.
false if the two arcs do not instersect.

See Also:

SmallCircle, SmallCircleArc, Scene

center

public Point center()

Find the center of the arc

Equations taken from the Aviation Formulary by Ed Williams.

Returns:

Point center_point The point at the center of the Arc.

densify

public Point[] densify(double distance_rad)

Densify the arc

Equations taken from the Aviation Formulary by Ed Williams.

Parameters:

distance_rad - The maximum distance in radians between points in the densified arc.

Returns:

Point[] dense_point A denser point set defining the same arc.

systemLog

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

Description copied from class: Sphere

Log diagnostic messages

Overrides:

systemLog in class GreatCircle