Package org.orekit.frames

Class TopocentricFrame

java.lang.Object

org.orekit.frames.Frame

org.orekit.frames.TopocentricFrame

All Implemented Interfaces:

Serializable, PVCoordinatesProvider

public class TopocentricFrame
extends Frame
implements PVCoordinatesProvider

Topocentric frame.

Frame associated to a position near the surface of a body shape.

The origin of the frame is at the defining geodetic point location, and the right-handed canonical trihedra is:

• X axis in the local horizontal plane (normal to zenith direction) and following the local parallel towards East
• Y axis in the horizontal plane (normal to zenith direction) and following the local meridian towards North
• Z axis towards Zenith direction

Author:

Véronique Pommier-Maurussane

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor	Description
TopocentricFrame(BodyShape parentShape, GeodeticPoint point, String name)	Simple constructor.

Method Summary

Modifier and Type	Method	Description
GeodeticPoint	computeLimitVisibilityPoint(double radius, double azimuth, double elevation)	Compute the limit visibility point for a satellite in a given direction.
double	getAzimuth(Vector3D extPoint, Frame frame, AbsoluteDate date)	Get the azimuth of a point with regards to the topocentric frame center point.
Vector3D	getEast()	Get the east direction of topocentric frame, expressed in parent shape frame.
double	getElevation(Vector3D extPoint, Frame frame, AbsoluteDate date)	Get the elevation of a point with regards to the local point.
Vector3D	getNadir()	Get the nadir direction of topocentric frame, expressed in parent shape frame.
Vector3D	getNorth()	Get the north direction of topocentric frame, expressed in parent shape frame.
BodyShape	getParentShape()	Get the body shape on which the local point is defined.
GeodeticPoint	getPoint()	Get the surface point defining the origin of the frame.
TimeStampedPVCoordinates	getPVCoordinates(AbsoluteDate date, Frame frame)	Get the PVCoordinates of the topocentric frame origin in the selected frame.
double	getRange(Vector3D extPoint, Frame frame, AbsoluteDate date)	Get the range of a point with regards to the topocentric frame center point.
double	getRangeRate(PVCoordinates extPV, Frame frame, AbsoluteDate date)	Get the range rate of a point with regards to the topocentric frame center point.
Vector3D	getSouth()	Get the south direction of topocentric frame, expressed in parent shape frame.
Vector3D	getWest()	Get the west direction of topocentric frame, expressed in parent shape frame.
Vector3D	getZenith()	Get the zenith direction of topocentric frame, expressed in parent shape frame.
GeodeticPoint	pointAtDistance(double azimuth, double elevation, double distance)	Compute the point observed from the station at some specified distance.

Methods inherited from class org.orekit.frames.Frame

getAncestor, getDepth, getFrozenFrame, getName, getParent, getRoot, getTransformProvider, getTransformTo, getTransformTo, isChildOf, isPseudoInertial, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

TopocentricFrame

public TopocentricFrame(BodyShape parentShape,
                        GeodeticPoint point,
                        String name)

Simple constructor.

Parameters:

parentShape - body shape on which the local point is defined

point - local surface point where topocentric frame is defined

name - the string representation

Method Detail

getParentShape

public BodyShape getParentShape()

Get the body shape on which the local point is defined.

Returns:

body shape on which the local point is defined

getPoint

public GeodeticPoint getPoint()

Get the surface point defining the origin of the frame.

Returns:

surface point defining the origin of the frame

getZenith

public Vector3D getZenith()

Get the zenith direction of topocentric frame, expressed in parent shape frame.

The zenith direction is defined as the normal to local horizontal plane.

Returns:

unit vector in the zenith direction

See Also:

getNadir()

getNadir

public Vector3D getNadir()

Get the nadir direction of topocentric frame, expressed in parent shape frame.

The nadir direction is the opposite of zenith direction.

Returns:

unit vector in the nadir direction

See Also:

getZenith()

getNorth

public Vector3D getNorth()

Get the north direction of topocentric frame, expressed in parent shape frame.

The north direction is defined in the horizontal plane (normal to zenith direction) and following the local meridian.

Returns:

unit vector in the north direction

See Also:

getSouth()

getSouth

public Vector3D getSouth()

Get the south direction of topocentric frame, expressed in parent shape frame.

The south direction is the opposite of north direction.

Returns:

unit vector in the south direction

See Also:

getNorth()

getEast

public Vector3D getEast()

Get the east direction of topocentric frame, expressed in parent shape frame.

The east direction is defined in the horizontal plane in order to complete direct triangle (east, north, zenith).

Returns:

unit vector in the east direction

See Also:

getWest()

getWest

public Vector3D getWest()

Get the west direction of topocentric frame, expressed in parent shape frame.

The west direction is the opposite of east direction.

Returns:

unit vector in the west direction

See Also:

getEast()

getElevation

public double getElevation(Vector3D extPoint,
                           Frame frame,
                           AbsoluteDate date)
                    throws OrekitException

Get the elevation of a point with regards to the local point.

The elevation is the angle between the local horizontal and the direction from local point to given point.

Parameters:

extPoint - point for which elevation shall be computed

frame - frame in which the point is defined

date - computation date

Returns:

elevation of the point

Throws:

OrekitException - if frames transformations cannot be computed

getAzimuth

public double getAzimuth(Vector3D extPoint,
                         Frame frame,
                         AbsoluteDate date)
                  throws OrekitException

Get the azimuth of a point with regards to the topocentric frame center point.

The azimuth is the angle between the North direction at local point and the projection in local horizontal plane of the direction from local point to given point. Azimuth angles are counted clockwise, i.e positive towards the East.

Parameters:

extPoint - point for which elevation shall be computed

frame - frame in which the point is defined

date - computation date

Returns:

azimuth of the point

Throws:

OrekitException - if frames transformations cannot be computed

getRange

public double getRange(Vector3D extPoint,
                       Frame frame,
                       AbsoluteDate date)
                throws OrekitException

Get the range of a point with regards to the topocentric frame center point.

Parameters:

extPoint - point for which range shall be computed

frame - frame in which the point is defined

date - computation date

Returns:

range (distance) of the point

Throws:

OrekitException - if frames transformations cannot be computed

getRangeRate

public double getRangeRate(PVCoordinates extPV,
                           Frame frame,
                           AbsoluteDate date)
                    throws OrekitException

Get the range rate of a point with regards to the topocentric frame center point.

Parameters:

extPV - point/velocity for which range rate shall be computed

frame - frame in which the point is defined

date - computation date

Returns:

range rate of the point (positive if point departs from frame)

Throws:

OrekitException - if frames transformations cannot be computed

computeLimitVisibilityPoint

public GeodeticPoint computeLimitVisibilityPoint(double radius,
                                                 double azimuth,
                                                 double elevation)
                                          throws OrekitException

Compute the limit visibility point for a satellite in a given direction.

This method can be used to compute visibility circles around ground stations for example, using a simple loop on azimuth, with either a fixed elevation or an elevation that depends on azimuth to take ground masks into account.

Parameters:

radius - satellite distance to Earth center

azimuth - pointing azimuth from station

elevation - pointing elevation from station

Returns:

limit visibility point for the satellite

Throws:

OrekitException - if point cannot be found

pointAtDistance

public GeodeticPoint pointAtDistance(double azimuth,
                                     double elevation,
                                     double distance)
                              throws OrekitException

Compute the point observed from the station at some specified distance.

Parameters:

azimuth - pointing azimuth from station

elevation - pointing elevation from station

distance - distance to station

Returns:

observed point

Throws:

OrekitException - if point cannot be computed

getPVCoordinates

public TimeStampedPVCoordinates getPVCoordinates(AbsoluteDate date,
                                                 Frame frame)
                                          throws OrekitException

Get the PVCoordinates of the topocentric frame origin in the selected frame.

Specified by:

getPVCoordinates in interface PVCoordinatesProvider

Parameters:

date - current date

frame - the frame where to define the position

Returns:

position/velocity of the topocentric frame origin (m and m/s)

Throws:

OrekitException - if position cannot be computed in given frame