org.orekit.models.earth.tessellation

Class AlongTrackAiming

java.lang.Object

org.orekit.models.earth.tessellation.AlongTrackAiming

All Implemented Interfaces:

TileAiming

public class AlongTrackAiming
extends Object
implements TileAiming

Class used to orient tiles along an orbit track.

Author:

Luc Maisonobe

See Also:

ConstantAzimuthAiming, DivertedSingularityAiming

Constructor Summary

Constructors

Constructor and Description
AlongTrackAiming(OneAxisEllipsoid ellipsoid, Orbit orbit, boolean isAscending) Simple constructor.

Method Summary

Modifier and Type	Method and Description
Vector3D	alongTileDirection(Vector3D point, GeodeticPoint gp) Find the along tile direction for tessellation at specified point.
List<GeodeticPoint>	getSingularPoints() Get points at which aiming direction cannot be computed.

Methods inherited from class java.lang.Object

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

Constructor Detail

AlongTrackAiming

public AlongTrackAiming(OneAxisEllipsoid ellipsoid,
                        Orbit orbit,
                        boolean isAscending)

Simple constructor.

Parameters:

ellipsoid - ellipsoid body on which the zone is defined

orbit - orbit along which tiles should be aligned

isAscending - indicator for zone tiling with respect to ascending or descending orbits

Method Detail

getSingularPoints

public List<GeodeticPoint> getSingularPoints()

Get points at which aiming direction cannot be computed.

As per Brouwer's hairy ball theorem, any vector field on the 2-sphere has at least one zero. This implies that any implementation of this interface has at least one point where the aiming direction cannot be computed. The most typical example is aiming always towards North pole, for which both poles are singular points.

Specified by:

getSingularPoints in interface TileAiming

Returns:

a non-empty (as per hairy ball theorem) list of points where aiming direction is either zero or cannot be computed

alongTileDirection

public Vector3D alongTileDirection(Vector3D point,
                                   GeodeticPoint gp)

Find the along tile direction for tessellation at specified point.

Specified by:

alongTileDirection in interface TileAiming

Parameters:

point - point on the ellipsoid (Cartesian coordinates)

gp - point on the ellipsoid (geodetic coordinates)

Returns:

normalized along tile direction