Package org.orekit.propagation.events

Class BooleanDetector

java.lang.Object

org.orekit.propagation.events.AbstractDetector<BooleanDetector>

org.orekit.propagation.events.BooleanDetector

All Implemented Interfaces:

Serializable, EventDetector

public class BooleanDetector
extends AbstractDetector<BooleanDetector>

This class provides AND and OR operations for event detectors. This class treats positive values of the g function as true and negative values as false.

One example for an imaging satellite might be to only detect events when a satellite is overhead (elevation > 0) AND when the ground point is sunlit (Sun elevation > 0). Another slightly contrived example using the OR operator would be to detect access to a set of ground stations and only report events when the satellite enters or leaves the field of view of the set, but not hand-offs between the ground stations.

For the BooleanDetector is important that the sign of the g function of the underlying event detector is not arbitrary, but has a semantic meaning, e.g. in or out, true or false. This class works well with event detectors that detect entry to or exit from a region, e.g. EclipseDetector, ElevationDetector, LatitudeCrossingDetector. Using this detector with detectors that are not based on entry to or exit from a region, e.g. DateDetector, LongitudeCrossingDetector, will likely lead to unexpected results. To apply conditions to this latter type of event detectors a EventEnablingPredicateFilter is usually more appropriate.

Author:

Evan Ward

See Also:

andCombine(Collection), orCombine(Collection), notCombine(EventDetector), EventEnablingPredicateFilter, EventSlopeFilter, Serialized Form

Field Summary

Fields inherited from class org.orekit.propagation.events.AbstractDetector

DEFAULT_MAX_ITER, DEFAULT_MAXCHECK, DEFAULT_THRESHOLD

Method Summary

Modifier and Type	Method	Description
static BooleanDetector	andCombine(Collection<? extends EventDetector> detectors)	Create a new event detector that is the logical AND of the given event detectors.
static BooleanDetector	andCombine(EventDetector... detectors)	Create a new event detector that is the logical AND of the given event detectors.
protected BooleanDetector	create(double newMaxCheck, double newThreshold, int newMaxIter, EventHandler<? super BooleanDetector> newHandler)	Build a new instance.
double	g(SpacecraftState s)	Compute the value of the switching function.
void	init(SpacecraftState s0, AbsoluteDate t)	Initialize event handler at the start of a propagation.
static NegateDetector	notCombine(EventDetector detector)	Create a new event detector that negates the g function of another detector.
static BooleanDetector	orCombine(Collection<? extends EventDetector> detectors)	Create a new event detector that is the logical OR or the given event detectors.
static BooleanDetector	orCombine(EventDetector... detectors)	Create a new event detector that is the logical OR or the given event detectors.

Methods inherited from class org.orekit.propagation.events.AbstractDetector

eventOccurred, getHandler, getMaxCheckInterval, getMaxIterationCount, getThreshold, isForward, resetState, withHandler, withMaxCheck, withMaxIter, withThreshold

Methods inherited from class java.lang.Object

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

Method Detail

andCombine

public static BooleanDetector andCombine(EventDetector... detectors)

Create a new event detector that is the logical AND of the given event detectors.

The created event detector's g function is positive if and only if the g functions of all detectors in detectors are positive.

The starting interval, threshold, and iteration count are set to the most stringent (minimum) of all the detectors. The event handlers of the underlying detectors are not used, instead the default handler is ContinueOnEvent.

Parameters:

detectors - the operands. Must contain at least one detector.

Returns:

a new event detector that is the logical AND of the operands.

Throws:

NoSuchElementException - if detectors is empty.

See Also:

BooleanDetector, andCombine(Collection), orCombine(EventDetector...), notCombine(EventDetector)

andCombine

public static BooleanDetector andCombine(Collection<? extends EventDetector> detectors)

Create a new event detector that is the logical AND of the given event detectors.

The created event detector's g function is positive if and only if the g functions of all detectors in detectors are positive.

The starting interval, threshold, and iteration count are set to the most stringent (minimum) of the detectors. The event handlers of the underlying detectors are not used, instead the default handler is ContinueOnEvent.

Parameters:

detectors - the operands. Must contain at least one detector.

Returns:

a new event detector that is the logical AND of the operands.

Throws:

NoSuchElementException - if detectors is empty.

See Also:

BooleanDetector, andCombine(EventDetector...), orCombine(Collection), notCombine(EventDetector)

orCombine

public static BooleanDetector orCombine(EventDetector... detectors)

Create a new event detector that is the logical OR or the given event detectors.

The created event detector's g function is positive if and only if at least one of g functions of the event detectors in detectors is positive.

The starting interval, threshold, and iteration count are set to the most stringent (minimum) of the detectors. The event handlers of the underlying EventDetectors are not used, instead the default handler is ContinueOnEvent.

Parameters:

detectors - the operands. Must contain at least one detector.

Returns:

a new event detector that is the logical OR of the operands.

Throws:

NoSuchElementException - if detectors is empty.

See Also:

BooleanDetector, orCombine(Collection), andCombine(EventDetector...), notCombine(EventDetector)

orCombine

public static BooleanDetector orCombine(Collection<? extends EventDetector> detectors)

Create a new event detector that is the logical OR or the given event detectors.

The created event detector's g function is positive if and only if at least one of g functions of the event detectors in detectors is positive.

The starting interval, threshold, and iteration count are set to the most stringent (minimum) of the detectors. The event handlers of the underlying EventDetectors are not used, instead the default handler is ContinueOnEvent.

Parameters:

detectors - the operands. Must contain at least one detector.

Returns:

a new event detector that is the logical OR of the operands.

Throws:

NoSuchElementException - if detectors is empty.

See Also:

BooleanDetector, orCombine(EventDetector...), andCombine(Collection), notCombine(EventDetector)

notCombine

public static NegateDetector notCombine(EventDetector detector)

Create a new event detector that negates the g function of another detector.

This detector will be initialized with the same EventDetector.getMaxCheckInterval(), EventDetector.getThreshold(), and EventDetector.getMaxIterationCount() as detector. The event handler of the underlying detector is not used, instead the default handler is ContinueOnEvent.

Parameters:

detector - to negate.

Returns:

an new event detector whose g function is the same magnitude but opposite sign of detector.

See Also:

andCombine(Collection), orCombine(Collection), BooleanDetector

g

public double g(SpacecraftState s)
         throws OrekitException

Description copied from class: AbstractDetector

Compute the value of the switching function. This function must be continuous (at least in its roots neighborhood), as the integrator will need to find its roots to locate the events.

Specified by:

g in interface EventDetector

Specified by:

g in class AbstractDetector<BooleanDetector>

Parameters:

s - the current state information: date, kinematics, attitude

Returns:

value of the switching function

Throws:

OrekitException - if some specific error occurs

create

protected BooleanDetector create(double newMaxCheck,
                                 double newThreshold,
                                 int newMaxIter,
                                 EventHandler<? super BooleanDetector> newHandler)

Description copied from class: AbstractDetector

Build a new instance.

Specified by:

create in class AbstractDetector<BooleanDetector>

Parameters:

newMaxCheck - maximum checking interval (s)

newThreshold - convergence threshold (s)

newMaxIter - maximum number of iterations in the event time search

newHandler - event handler to call at event occurrences

Returns:

a new instance of the appropriate sub-type

init

public void init(SpacecraftState s0,
                 AbsoluteDate t)
          throws OrekitException

Description copied from class: AbstractDetector

Initialize event handler at the start of a propagation.

This method is called once at the start of the propagation. It may be used by the event handler to initialize some internal data if needed.

The default implementation does nothing

This implementation sets the direction of propagation and initializes the event handler. If a subclass overrides this method it should call super.init(s0, t).

Specified by:

init in interface EventDetector

Overrides:

init in class AbstractDetector<BooleanDetector>

Parameters:

s0 - initial state

t - target time for the integration

Throws:

OrekitException - if some specific error occurs