edu.nrao.sss.astronomy
Class SimpleSkyPosition

java.lang.Object
  edu.nrao.sss.astronomy.SimpleSkyPosition

All Implemented Interfaces:

SkyPosition, SphericalPosition, Cloneable

public class SimpleSkyPosition
extends Object

A very basic implementation of a sky position.

Version Info:

$Revision: 1156 $

$Date: 2008-03-12 11:43:13 -0600 (Wed, 12 Mar 2008) $

$Author: dharland $

Since:

2007-04-17

Author:

David M. Harland

Constructor Summary

SimpleSkyPosition()
Creates a new equatorial, J2000, position.

SimpleSkyPosition(CelestialCoordinateSystem system, Epoch epoch)
Creates a new instance with the given properties.

Method Summary

SimpleSkyPosition	clone() Returns a copy of this sky position.
boolean	equals(Object o) Returns true if o is equal to this position.
Angle	getAngularSeparation(SphericalPosition other) Calculates the current angular separation between this position and other.
Angle	getAngularSeparation(SphericalPosition other, Date time) Calculates current angular separation between this position and other at the given time.
CelestialCoordinateSystem	getCoordinateSystem() Returns the coordinate system to use when interpreting the latitude and longitude values of this position.
Distance	getDistance() Returns the current distance of this position.
Distance	getDistance(Date time) Returns the distance of this position at the given point in time.
Distance	getDistanceUncertainty() Returns the uncertainty in the distance of this position.
Epoch	getEpoch() Returns the epoch on which this position is based.
Latitude	getLatitude() Returns the current latitude of this position.
Latitude	getLatitude(Date time) Returns the latitude of this position at the given point in time.
Latitude	getLatitudeUncertainty() Returns the uncertainty in the latitude of this position.
Longitude	getLongitude() Returns the current longitude of this position.
Longitude	getLongitude(Date time) Returns the longitude of this position at the given point in time.
Longitude	getLongitudeUncertainty() Returns the uncertainty in the longitude of this position.
String	getOriginOfInformation() Returns the origin of this position's information.
SkyPositionType	getType() Provides a hint as to how this position stores its information.
int	hashCode() Returns a hash code value for this position.
boolean	isMoving() Returns true if this position has different properties at time T than it does at time U ≠ T.
void	reset() Puts this instance into the same state as one newly created via the no-argument constructor.
void	setCoordinateSystem(CelestialCoordinateSystem newSystem) Sets the system of latitude and longitude on which this position is based.
void	setDistance(Distance newDistance) Sets the distance of this position.
void	setDistanceUncertainty(Distance newUncertainty) Sets the uncertainty in the distance of this position.
void	setEpoch(Epoch newEpoch) Sets the epoch on which this position is based.
void	setLatitude(Latitude newLatitude) Sets the latitude of this position.
void	setLatitudeUncertainty(Latitude newUncertainty) Sets the uncertainty in the latitude of this position.
void	setLongitude(Longitude newLongitude) Sets the longitude of this position.
void	setLongitudeUncertainty(Longitude newUncertainty) Sets the uncertainty in the longitude of this position.
void	setOriginOfInformation(String origin) Sets the origin of this position's information.
PolynomialPosition	toPolynomialPosition() Creates and returns a new polynomial position whose time-zero values are the same as those of this position.
SkyPosition	toPosition(CelestialCoordinateSystem system, Epoch epoch, EarthPosition observer, LocalSiderealTime lst) Returns a new position expressed in the given coordinate system and epoch that is equivalent to this position.
SkyPosition	toPosition(CelestialCoordinateSystem system, Epoch epoch, EarthPosition observer, LocalSiderealTime lst, CelestialCoordinateConverter converter) Returns a new position expressed in the given coordinate system and epoch that is equivalent to this position.
String	toString()

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

SimpleSkyPosition

public SimpleSkyPosition()

Creates a new equatorial, J2000, position.

SimpleSkyPosition

public SimpleSkyPosition(CelestialCoordinateSystem system,
                         Epoch epoch)

Creates a new instance with the given properties.

Method Detail

reset

public void reset()

Puts this instance into the same state as one newly created via the no-argument constructor.

getType

public SkyPositionType getType()

Description copied from interface: SkyPosition

Provides a hint as to how this position stores its information.

Returns:

a hint as to how this position stores its information.

isMoving

public boolean isMoving()

Description copied from interface: SkyPosition

Returns true if this position has different properties at time T than it does at time U ≠ T.

The determination of motion will be made with respect to the coordinate system in which this position is expressed. For example, a position that is expressed in the equatorial system, and that is holding steady at its position in that system, will said to be not moving, even though in other coordinate systems it may be moving quite rapidly.

Returns:

true if this position is moving.

setLongitude

public void setLongitude(Longitude newLongitude)

Sets the longitude of this position.

If newLongitude is null, this method creates, and saves a reference to, a new longitude object. Otherwise it saves a reference to newLongitude. This means that any changes made to (a non-null) newLongitude by clients after this call will be reflected in this position.

Parameters:

newLongitude - a new longitude for this position.

getLongitude

public Longitude getLongitude()

Returns the current longitude of this position.

The returned object is guaranteed to be non-null and is also a reference to the internal longitude held by this position. This means any changes made by clients to the returned object will be reflected in this position.

Specified by:

getLongitude in interface SphericalPosition

Returns:

the current longitude of this position.

setLatitude

public void setLatitude(Latitude newLatitude)

Sets the latitude of this position.

If newLatitude is null, this method creates, and saves a reference to, a new latitude object. Otherwise it saves a reference to newLatitude. This means that any changes made to (a non-null) newLatitude by clients after this call will be reflected in this position.

Parameters:

newLatitude - a new latitude for this position.

getLatitude

public Latitude getLatitude()

Returns the current latitude of this position.

The returned object is guaranteed to be non-null and is also a reference to the internal latitude held by this position. This means any changes made by clients to the returned object will be reflected in this position.

Specified by:

getLatitude in interface SphericalPosition

Returns:

the current latitude of this position.

setDistance

public void setDistance(Distance newDistance)

Sets the distance of this position.

If newDistance is null, this method creates, and saves a reference to, a new distance object. Otherwise it saves a reference to newDistance. This means that any changes made to (a non-null) newDistance by clients after this call will be reflected in this position.

Parameters:

newDistance - a new distance for this position.

getDistance

public Distance getDistance()

Returns the current distance of this position.

The returned object is guaranteed to be non-null and is also a reference to the internal distance held by this position. This means any changes made by clients to the returned object will be reflected in this position.

Specified by:

getDistance in interface SphericalPosition

Returns:

the current distance of this position.

getLongitude

public Longitude getLongitude(Date time)

Returns the longitude of this position at the given point in time.

The returned object is guaranteed to be non-null and is also a reference to the internal longitude held by this position. This means any changes made by clients to the returned object will be reflected in this position.

Since this class has no concept of time, the value returned here will be the same as that returned by the corresponding no-argument method.

Parameters:

time - the point in time for which the longitude is sought.

Returns:

the longitude of this position at the given point in time.

getLatitude

public Latitude getLatitude(Date time)

Returns the latitude of this position at the given point in time.

The returned object is guaranteed to be non-null and is also a reference to the internal latitude held by this position. This means any changes made by clients to the returned object will be reflected in this position.

Since this class has no concept of time, the value returned here will be the same as that returned by the corresponding no-argument method.

Parameters:

time - the point in time for which the latitude is sought.

Returns:

the latitude of this position at the given point in time.

getDistance

public Distance getDistance(Date time)

Returns the distance of this position at the given point in time.

The returned object is guaranteed to be non-null and is also a reference to the internal distance held by this position. This means any changes made by clients to the returned object will be reflected in this position.

Since this class has no concept of time, the value returned here will be the same as that returned by the corresponding no-argument method.

Parameters:

time - the point in time for which the distance is sought.

Returns:

the distance at the given point in time.

setLongitudeUncertainty

public void setLongitudeUncertainty(Longitude newUncertainty)

Sets the uncertainty in the longitude of this position.

If newUncertainty is null, this method creates, and saves a reference to, a new longitude object. Otherwise it saves a reference to newUncertainty. This means that any changes made to (a non-null) newUncertainty by clients after this call will be reflected in this position.

Parameters:

newUncertainty - a new value for the uncertainty of the longitude of this position.

getLongitudeUncertainty

public Longitude getLongitudeUncertainty()

Returns the uncertainty in the longitude of this position.

The returned object is guaranteed to be non-null and is also a reference to the internal uncertainty held by this position. This means any changes made by clients to the returned object will be reflected in this position.

Specified by:

getLongitudeUncertainty in interface SphericalPosition

Returns:

the uncertainty in the longitude of this position.

setLatitudeUncertainty

public void setLatitudeUncertainty(Latitude newUncertainty)

Sets the uncertainty in the latitude of this position.

If newUncertainty is null, this method creates, and saves a reference to, a new latitude object. Otherwise it saves a reference to newUncertainty. This means that any changes made to (a non-null) newUncertainty by clients after this call will be reflected in this position.

Parameters:

newUncertainty - a new value for the uncertainty of the latitude of this position.

getLatitudeUncertainty

public Latitude getLatitudeUncertainty()

Returns the uncertainty in the latitude of this position.

The returned object is guaranteed to be non-null and is also a reference to the internal uncertainty held by this position. This means any changes made by clients to the returned object will be reflected in this position.

Specified by:

getLatitudeUncertainty in interface SphericalPosition

Returns:

the uncertainty in the latitude of this position.

setDistanceUncertainty

public void setDistanceUncertainty(Distance newUncertainty)

Sets the uncertainty in the distance of this position.

If newUncertainty is null, this method creates, and saves a reference to, a new distance object. Otherwise it saves a reference to newUncertainty. This means that any changes made to (a non-null) newUncertainty by clients after this call will be reflected in this position.

Parameters:

newUncertainty - a new value for the uncertainty of the distance of this position.

getDistanceUncertainty

public Distance getDistanceUncertainty()

Returns the uncertainty in the distance of this position.

The returned object is guaranteed to be non-null and is also a reference to the internal uncertainty held by this position. This means any changes made by clients to the returned object will be reflected in this position.

Specified by:

getDistanceUncertainty in interface SphericalPosition

Returns:

the uncertainty in the distance of this position.

toPolynomialPosition

public PolynomialPosition toPolynomialPosition()

Creates and returns a new polynomial position whose time-zero values are the same as those of this position. The returned position has a default reference time and a default valid time interval.

Returns:

a new polynomial position based on this position.

toString

public String toString()

Overrides:

toString in class Object

clone

public SimpleSkyPosition clone()

Returns a copy of this sky position.

If anything goes wrong during the cloning procedure, a RuntimeException will be thrown.

Specified by:

clone in interface SkyPosition

Specified by:

clone in interface SphericalPosition

Returns:

a copy of this sky position.

equals

public boolean equals(Object o)

Returns true if o is equal to this position.

hashCode

public int hashCode()

Returns a hash code value for this position.

setCoordinateSystem

public void setCoordinateSystem(CelestialCoordinateSystem newSystem)

Sets the system of latitude and longitude on which this position is based. If newSystem is null, this method does nothing.

Parameters:

newSystem - the system of latitude and longitude on which this position is based.

getCoordinateSystem

public CelestialCoordinateSystem getCoordinateSystem()

Description copied from interface: SkyPosition

Returns the coordinate system to use when interpreting the latitude and longitude values of this position.

Specified by:

getCoordinateSystem in interface SkyPosition

Returns:

the system of latitude and longitude used by this position.

setEpoch

public void setEpoch(Epoch newEpoch)

Sets the epoch on which this position is based. If newEpoch is null, this method does nothing.

Parameters:

newEpoch - the epoch on which this position is based.

getEpoch

public Epoch getEpoch()

Description copied from interface: SkyPosition

Returns the epoch on which this position is based.

Specified by:

getEpoch in interface SkyPosition

Returns:

the epoch on which this position is based.

setOriginOfInformation

public void setOriginOfInformation(String origin)

Sets the origin of this position's information.

Parameters:

origin - the origin of this position's information. A value of null will be replaced by a non-null default value.

getOriginOfInformation

public String getOriginOfInformation()

Description copied from interface: SkyPosition

Returns the origin of this position's information.

Specified by:

getOriginOfInformation in interface SkyPosition

Returns:

the origin of this position's information.

toPosition

public SkyPosition toPosition(CelestialCoordinateSystem system,
                              Epoch epoch,
                              EarthPosition observer,
                              LocalSiderealTime lst)
                       throws CoordinateConversionException

Description copied from interface: SkyPosition

Returns a new position expressed in the given coordinate system and epoch that is equivalent to this position. This position is not changed by this method.

Specified by:

toPosition in interface SkyPosition

Parameters:

system - the celestial coordinate system of the returned position.

epoch - the epoch of the returned position.

observer - the location of the observer. This value is used almost exclusively for conversions to or from the HORIZONTAL (az/el) coordinate system. If a given conversion does not require this parameter, a null value will do no harm.

lst - the local sidereal time at the observer's location. This parameter serves two purposes. First, it is integral in conversions to or from the HORIZONTAL (az/el) coordinate system. Second, even for conversions that do not depend on the observer's location, the conversion method will use the UTC time represented by this LST to determine the exact location of this position before converting it to another system. When used this way the location associated with the LST is immaterial. If this value is null it will be replaced with the current time. Using a null value is not recommended when dealing with the HORIZONTAL system because the LST may not be for the location of interest.

Returns:

a new position with a coordinate system of system, and epoch of epoch, and coordinates that represent a conversion from those of this position.

Throws:

CoordinateConversionException - if anything goes wrong with the conversion.

toPosition

public SkyPosition toPosition(CelestialCoordinateSystem system,
                              Epoch epoch,
                              EarthPosition observer,
                              LocalSiderealTime lst,
                              CelestialCoordinateConverter converter)
                       throws CoordinateConversionException

Description copied from interface: SkyPosition

Returns a new position expressed in the given coordinate system and epoch that is equivalent to this position. This position is not changed by this method.

Specified by:

toPosition in interface SkyPosition

Parameters:

system - the celestial coordinate system of the returned position.

epoch - the epoch of the returned position.

observer - the location of the observer. This value is used almost exclusively for conversions to or from the HORIZONTAL (az/el) coordinate system.

lst - the local sidereal time at the observer's location. This parameter serves two purposes. First, it is integral in conversions to or from the HORIZONTAL (az/el) coordinate system. Second, even for conversions that do not depend on the observer's location, the conversion method will use the UTC time represented by this LST to determine the exact location of this position before converting it to another system. When used this way the location associated with the LST is immaterial. If this value is null it will be replaced with the current time. Using a null value is not recommended when dealing with the HORIZONTAL system because the LST may not be for the location of interest.

converter - the converter used to perform the transformation.

Returns:

a new position with a coordinate system of system, and epoch of epoch, and coordinates that represent a conversion from those of this position.

Throws:

CoordinateConversionException - if anything goes wrong with the conversion.

getAngularSeparation

public Angle getAngularSeparation(SphericalPosition other)

Description copied from interface: SphericalPosition

Calculates the current angular separation between this position and other.

The distances of the positions from the center of the sphere are not considered. The returned angle is the smallest possible such angle. It is the angular size of the arc of a great circle that passes through both the ray from the orgin to this position and the ray from the origin to other.

The returned value is never negative. This means that the returned angle does not contain directional information. That is, the angle from A to B is exactly equal to the angle from B to A.

Specified by:

getAngularSeparation in interface SphericalPosition

Parameters:

other - a position from which this one is separated by the returned angle.

Returns:

the angle of separation between this position and other.

getAngularSeparation

public Angle getAngularSeparation(SphericalPosition other,
                                  Date time)

Description copied from interface: SkyPosition

Calculates current angular separation between this position and other at the given time.

The distances of the positions from the center of the sphere are not considered. The returned angle is the smallest possible such angle. It is the angular size of the arc of a great circle that passes through both the ray from the orgin to this position and the ray from the origin to other.

The returned value is never negative. This means that the returned angle does not contain directional information. That is, the angle from A to B is exactly equal to the angle from B to A.

Specified by:

getAngularSeparation in interface SkyPosition

Parameters:

other - a position from which this one is separated by the returned angle.

time - the point in time for which the separation is sought.

Returns:

the angle of separation between this position and other.