org.orekit.bodies

Class OneAxisEllipsoid

java.lang.Object

org.orekit.bodies.Ellipsoid

org.orekit.bodies.OneAxisEllipsoid

All Implemented Interfaces:

Serializable, BodyShape

public class OneAxisEllipsoid
extends Ellipsoid
implements BodyShape

Modeling of a one-axis ellipsoid.

One-axis ellipsoids is a good approximate model for most planet-size and larger natural bodies. It is the equilibrium shape reached by a fluid body under its own gravity field when it rotates. The symmetry axis is the rotation or polar axis.

Author:

Luc Maisonobe

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
OneAxisEllipsoid(double ae, double f, Frame bodyFrame) Simple constructor.

Method Summary

Methods

Modifier and Type	Method and Description
Frame	getBodyFrame() Get body frame related to body shape.
double	getEquatorialRadius() Get the equatorial radius of the body.
double	getFlattening() Get the flattening of the body: f = (a-b)/a.
GeodeticPoint	getIntersectionPoint(Line line, Vector3D close, Frame frame, AbsoluteDate date) Get the intersection point of a line with the surface of the body.
TimeStampedPVCoordinates	projectToGround(TimeStampedPVCoordinates pv, Frame frame) Project a moving point to the ground.
Vector3D	projectToGround(Vector3D point, AbsoluteDate date, Frame frame) Project a point to the ground.
void	setAngularThreshold(double angularThreshold) Set the angular convergence threshold.
Vector3D	transform(GeodeticPoint point) Transform a surface-relative point to a cartesian point.
GeodeticPoint	transform(Vector3D point, Frame frame, AbsoluteDate date) Transform a cartesian point to a surface-relative point.

Methods inherited from class org.orekit.bodies.Ellipsoid

getA, getB, getC, getFrame, getPlaneSection

Methods inherited from class java.lang.Object

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

Constructor Detail

OneAxisEllipsoid

public OneAxisEllipsoid(double ae,
                double f,
                Frame bodyFrame)

Simple constructor.

The following table provides conventional parameters for global Earth models:

model	ae (m)	f
GRS 80	6378137.0	1.0 / 298.257222101
WGS84	6378137.0	1.0 / 298.257223563

Parameters:

ae - equatorial radius

f - the flattening (f = (a-b)/a)

bodyFrame - body frame related to body shape

See Also:

FramesFactory.getITRF(org.orekit.utils.IERSConventions, boolean)

Method Detail

setAngularThreshold

public void setAngularThreshold(double angularThreshold)

Set the angular convergence threshold.

The angular threshold is used both to identify points close to the ellipse axes and as the convergence threshold used to stop the iterations in the transform(Vector3D, Frame, AbsoluteDate) method.

If this method is not called, the default value is set to 10^-12.

Parameters:

angularThreshold - angular convergence threshold (rad)

getEquatorialRadius

public double getEquatorialRadius()

Get the equatorial radius of the body.

Returns:

equatorial radius of the body (m)

getFlattening

public double getFlattening()

Get the flattening of the body: f = (a-b)/a.

Returns:

the flattening

getBodyFrame

public Frame getBodyFrame()

Get body frame related to body shape.

Specified by:

getBodyFrame in interface BodyShape

Returns:

body frame related to body shape

getIntersectionPoint

public GeodeticPoint getIntersectionPoint(Line line,
                                 Vector3D close,
                                 Frame frame,
                                 AbsoluteDate date)
                                   throws OrekitException

Get the intersection point of a line with the surface of the body.

A line may have several intersection points with a closed surface (we consider the one point case as a degenerated two points case). The close parameter is used to select which of these points should be returned. The selected point is the one that is closest to the close point.

Specified by:

getIntersectionPoint in interface BodyShape

Parameters:

line - test line (may intersect the body or not)

close - point used for intersections selection

frame - frame in which line is expressed

date - date of the line in given frame

Returns:

intersection point at altitude zero or null if the line does not intersect the surface

Throws:

OrekitException - if line cannot be converted to body frame

transform

public Vector3D transform(GeodeticPoint point)

Transform a surface-relative point to a cartesian point.

Specified by:

transform in interface BodyShape

Parameters:

point - surface-relative point

Returns:

point at the same location but as a cartesian point

projectToGround

public Vector3D projectToGround(Vector3D point,
                       AbsoluteDate date,
                       Frame frame)
                         throws OrekitException

Project a point to the ground.

Specified by:

projectToGround in interface BodyShape

Parameters:

point - point to project

date - current date

frame - frame in which moving point is expressed

Returns:

ground point exactly at the local vertical of specified point, in the same frame as specified point

Throws:

OrekitException - if point cannot be converted to body frame

See Also:

BodyShape.projectToGround(TimeStampedPVCoordinates, Frame)

projectToGround

public TimeStampedPVCoordinates projectToGround(TimeStampedPVCoordinates pv,
                                       Frame frame)
                                         throws OrekitException

Project a moving point to the ground.

Specified by:

projectToGround in interface BodyShape

Parameters:

pv - moving point

frame - frame in which moving point is expressed

Returns:

ground point exactly at the local vertical of specified point, in the same frame as specified point

Throws:

OrekitException - if point cannot be converted to body frame

See Also:

BodyShape.projectToGround(Vector3D, AbsoluteDate, Frame)

transform

public GeodeticPoint transform(Vector3D point,
                      Frame frame,
                      AbsoluteDate date)
                        throws OrekitException

Transform a cartesian point to a surface-relative point.

Specified by:

transform in interface BodyShape

Parameters:

point - cartesian point

frame - frame in which cartesian point is expressed

date - date of the computation (used for frames conversions)

Returns:

point at the same location but as a surface-relative point

Throws:

OrekitException - if point cannot be converted to body frame