agi.foundation.propagators

(agi.foundation.navigation-2024r1.jar)

Class GpsRinexPropagator

java.lang.Object

agi.foundation.infrastructure.DefinitionalObject

agi.foundation.propagators.CartesianOnePointPropagator

agi.foundation.propagators.GpsRinexPropagator

All Implemented Interfaces:

ICloneWithContext, IEnumerateDependencies, IEquatableDefinition, IFreezable, IAvailability

public class GpsRinexPropagator
extends CartesianOnePointPropagator
implements IAvailability

GPS RINEX Propagator class propagates GPS orbits - providing GPS satellite positions based on RINEX broadcast ephemeris sets.

The propagation scheme in the GPS Propagator is defined in the Interface Specification IS-GPS-200D. The IS can be found at the US Coast Guard Navigation Center website: IS GPS-200D

IS-GPS-200D states that element sets should not be used beyond their curve fit interval. Currently, if the time you evaluate the propagator at is outside the element set's epoch (before or after), a propagation will still occur. Any limiting must be done by the user of the propagator.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	GpsRinexPropagator(GpsRinexPropagator existingInstance, CopyContext context) Initializes a new instance as a copy of an existing instance.
	GpsRinexPropagator(RinexNavigationRecord gpsRecord) Creates a propagator based upon a RinexNavigationRecord.

Method Summary

Modifier and Type	Method and Description
protected boolean	checkForSameDefinition(CartesianOnePointPropagator other) Checks to determine if another instance has the same definition as this instance and returns true if it does.
protected boolean	checkForSameDefinition(GpsRinexPropagator other) Checks to determine if another instance has the same definition as this instance and returns true if it does.
Object	clone(CopyContext context) Clones this object using the specified context.
protected int	computeCurrentDefinitionHashCode() Computes a hash code based on the current properties of this object.
void	enumerateDependencies(DependencyEnumerator enumerator) Enumerates the dependencies of this object by calling DependencyEnumerator#enumerate(T) for each object that this object directly depends upon.
protected void	freezeAggregatedObjects() Called by DefinitionalObject.freeze() to also freeze any objects that are considered to be a part of this object.
TimeIntervalCollection	getAvailabilityIntervals() Gets a TimeIntervalCollection over which data is available.
TimeIntervalCollection	getAvailabilityIntervals(TimeIntervalCollection consideredIntervals) Gets the intervals over which data is available.
BehaviorBeyondAvailability	getEvaluationBehavior() Gets the type of behavior the GpsRinexPropagator will have when it is evaluated beyond its AvailabilityIntervals (get).
MotionEvaluator1<Cartesian>	getEvaluator(EvaluatorGroup group) Gets an evaluator that can propagate at individual dates.
protected ReferenceFrame	getMotionReferenceFrame() Gets the reference frame in which the motion is defined.
ReferenceFrame	getReferenceFrame() Gets the Earth Fixed reference frame, which is the frame that the GPS satellite orbital positions are referenced to.
boolean	isAvailable(JulianDate date) Determines if valid data is available for the given JulianDate.
void	setEvaluationBehavior(BehaviorBeyondAvailability value) Sets the type of behavior the GpsRinexPropagator will have when it is evaluated beyond its AvailabilityIntervals (get).

Methods inherited from class agi.foundation.propagators.CartesianOnePointPropagator

checkForSameDefinition, createPoint, getEvaluator, propagate, propagate

Methods inherited from class agi.foundation.infrastructure.DefinitionalObject

areSameDefinition, areSameDefinition, areSameDefinition, areSameDefinition, areSameDefinition, collectionItemsAreSameDefinition, collectionItemsAreSameDefinition, collectionItemsAreSameDefinition, dictionaryItemsAreSameDefinition, freeze, getCollectionHashCode, getCollectionHashCode, getCollectionHashCode, getDefinitionHashCode, getDefinitionHashCode, getDefinitionHashCode, getDefinitionHashCode, getDefinitionHashCode, getDefinitionHashCode, getDictionaryHashCode, getIsFrozen, isSameDefinition, throwIfFrozen

Methods inherited from class java.lang.Object

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

Constructor Detail

GpsRinexPropagator

public GpsRinexPropagator(RinexNavigationRecord gpsRecord)

Creates a propagator based upon a RinexNavigationRecord.

Parameters:

gpsRecord - The record containing all the ephemeris data for this satellite.

GpsRinexPropagator

protected GpsRinexPropagator(@Nonnull
                             GpsRinexPropagator existingInstance,
                             @Nonnull
                             CopyContext context)

Initializes a new instance as a copy of an existing instance.

See ICloneWithContext.clone(CopyContext) for more information about how to implement this constructor in a derived class.

Parameters:

existingInstance - The existing instance to copy.

context - A CopyContext that controls the depth of the copy.

Throws:

ArgumentNullException - Thrown when existingInstance or context is null.

Method Detail

clone

public Object clone(CopyContext context)

Clones this object using the specified context.

This method should be implemented to call a copy constructor on the class of the object being cloned. The copy constructor should take the CopyContext as a parameter in addition to the existing instance to copy. The copy constructor should first call CopyContext.addObjectMapping(T, T) to identify the newly constructed instance as a copy of the existing instance. It should then copy all fields, using CopyContext.updateReference(T) to copy any reference fields.

A typical implementation of ICloneWithContext:

public static class MyClass implements ICloneWithContext {
    public MyClass(MyClass existingInstance, CopyContext context) {
        context.addObjectMapping(existingInstance, this);
        someReference = context.updateReference(existingInstance.someReference);
    }

    @Override
    public final Object clone(CopyContext context) {
        return new MyClass(this, context);
    }

    private Object someReference;
}

In general, all fields that are reference types should be copied with a call to CopyContext.updateReference(T). There are a couple of exceptions:

1. Fields that are aggregate parts of the object should always be copied. A referenced object is an aggregate if properties or methods on the object being copied can modify the externally-visible value of the referenced object.
2. If the semantics of the referenced object require that it have a single parent, owner, context, etc., and the object being copied is that parent, owner, or context, then the referenced object should always be copied.

If one of these exceptions applies, the CopyContext should be given an opportunity to update the reference before the reference is copied explicitly. Use CopyContext.updateReference(T) to update the reference. If CopyContext.updateReference(T) returns the original object, indicating that the context does not have a replacement registered, then copy the object manually by invoking a Clone method, a copy constructor, or by manually constructing a new instance and copying the values.

alwaysCopy = context.updateReference(existingInstance.alwaysCopy);
if (existingInstance.alwaysCopy != null && alwaysCopy == existingInstance.alwaysCopy) {
    alwaysCopy = (AlwaysCopy) existingInstance.alwaysCopy.clone(context);
}

If you are implementing an evaluator (a class that implements IEvaluator), the IEvaluator.updateEvaluatorReferences(agi.foundation.infrastructure.CopyContext) method shares some responsibilities with the copy context constructor. Code duplication can be avoided by doing the following:

1. For references to other evaluators ONLY, simply assign the reference in the constructor instead of calling CopyContext.updateReference(T). You should still call CopyContext.updateReference(T) on any references to non-evaluators.
2. Call IEvaluator.updateEvaluatorReferences(agi.foundation.infrastructure.CopyContext) as the last line in the constructor and pass it the same CopyContext passed to the constructor.
3. Implement IEvaluator.updateEvaluatorReferences(agi.foundation.infrastructure.CopyContext) as normal. See the reference documentation for IEvaluator.updateEvaluatorReferences(agi.foundation.infrastructure.CopyContext) for more information on implementing that method.

public MyClass(MyClass existingInstance, CopyContext context) {
    super(existingInstance, context);
    someReference = context.updateReference(existingInstance.someReference);
    evaluatorReference = existingInstance.evaluatorReference;
    updateEvaluatorReferences(context);
}

@Override
public void updateEvaluatorReferences(CopyContext context) {
    evaluatorReference = context.updateReference(evaluatorReference);
}

@Override
public Object clone(CopyContext context) {
    return new MyClass(this, context);
}

private Object someReference;
private IEvaluator evaluatorReference;

Specified by:

clone in interface ICloneWithContext

Specified by:

clone in class DefinitionalObject

Parameters:

context - The context to use to perform the copy.

Returns:

A new instance which is a copy of this object.

checkForSameDefinition

protected final boolean checkForSameDefinition(CartesianOnePointPropagator other)

Checks to determine if another instance has the same definition as this instance and returns true if it does. Derived classes MUST override this method and check all new fields introduced by the derived class for definitional equivalence. It is NOT necessary to check base class fields because the base class will already have done that. When overriding this method, you should NOT call the base implementation because it will return false for all derived-class instances. Derived classes should check the type of other to preserve the symmetric nature of IEquatableDefinition.isSameDefinition(java.lang.Object).

Specified by:

checkForSameDefinition in class CartesianOnePointPropagator

Parameters:

other - The other instance to compare to this one.

Returns:

true if the two objects are defined equivalently; otherwise false.

checkForSameDefinition

protected boolean checkForSameDefinition(GpsRinexPropagator other)

Checks to determine if another instance has the same definition as this instance and returns true if it does. Derived classes MUST override this method and check all new fields introduced by the derived class for definitional equivalence. It is NOT necessary to check base class fields because the base class will already have done that. When overriding this method, you should NOT call the base implementation because it will return false for all derived-class instances. Derived classes should check the type of other to preserve the symmetric nature of IEquatableDefinition.isSameDefinition(java.lang.Object).

Parameters:

other - The other instance to compare to this one.

Returns:

true if the two objects are defined equivalently; otherwise false.

computeCurrentDefinitionHashCode

protected int computeCurrentDefinitionHashCode()

Computes a hash code based on the current properties of this object. Derived classes MUST override this method and compute a hash code that combines: a unique hash code seed, the base implementation result, and the hash codes of all new fields introduced by the derived class which are used in the GpsRinexPropagator.checkForSameDefinition(agi.foundation.propagators.CartesianOnePointPropagator) method.

Overrides:

computeCurrentDefinitionHashCode in class CartesianOnePointPropagator

Returns:

The computed hash code.

enumerateDependencies

public void enumerateDependencies(DependencyEnumerator enumerator)

Enumerates the dependencies of this object by calling DependencyEnumerator#enumerate(T) for each object that this object directly depends upon. Derived classes which contain additional dependencies MUST override this method, call the base implementation, and enumerate dependencies introduced by the derived class.

Specified by:

enumerateDependencies in interface IEnumerateDependencies

Overrides:

enumerateDependencies in class DefinitionalObject

Parameters:

enumerator - The enumerator that is informed of the dependencies of this object.

freezeAggregatedObjects

protected void freezeAggregatedObjects()

Called by DefinitionalObject.freeze() to also freeze any objects that are considered to be a part of this object. Derived classes which contain additional aggregated objects MUST override this method, call the base implementation, and freeze aggregated objects introduced by the derived class. The objects that need to be frozen in this method are frequently created in this object's constructor and are not settable via properties.

Overrides:

freezeAggregatedObjects in class DefinitionalObject

getAvailabilityIntervals

public TimeIntervalCollection getAvailabilityIntervals(TimeIntervalCollection consideredIntervals)

Gets the intervals over which data is available.

Specified by:

getAvailabilityIntervals in interface IAvailability

Parameters:

consideredIntervals - The intervals over which availability information is needed. Note that the returned availability intervals may indicate availability outside of these intervals of consideration.

Returns:

The collection of availability intervals.

isAvailable

public final boolean isAvailable(@Nonnull
                                 JulianDate date)

Determines if valid data is available for the given JulianDate.

Specified by:

isAvailable in interface IAvailability

Parameters:

date - The date for which to check availability.

Returns:

true if valid data is available for this date; otherwise false.

getAvailabilityIntervals

@Nonnull
public final TimeIntervalCollection getAvailabilityIntervals()

Gets a TimeIntervalCollection over which data is available. If the availability interval is infinite, this returns Infinite (get).

It is recommended that you call GpsRinexPropagator.isAvailable(agi.foundation.time.JulianDate) to determine availability instead of calling this method and checking for yourself.

Returns:

The collection of availability intervals.

getReferenceFrame

public final ReferenceFrame getReferenceFrame()

Gets the Earth Fixed reference frame, which is the frame that the GPS satellite orbital positions are referenced to.

The Earth Fixed frame is obtained from the FixedFrame (get / set) property of the EarthCentralBody that is stored in the CentralBodiesFacet instance in the CalculationContext.

getEvaluationBehavior

@Nonnull
public final BehaviorBeyondAvailability getEvaluationBehavior()

Gets the type of behavior the GpsRinexPropagator will have when it is evaluated beyond its AvailabilityIntervals (get). The default behavior is BehaviorBeyondAvailability.EXTRAPOLATE.

setEvaluationBehavior

public final void setEvaluationBehavior(@Nonnull
                                        BehaviorBeyondAvailability value)

Sets the type of behavior the GpsRinexPropagator will have when it is evaluated beyond its AvailabilityIntervals (get). The default behavior is BehaviorBeyondAvailability.EXTRAPOLATE.

getMotionReferenceFrame

protected ReferenceFrame getMotionReferenceFrame()

Gets the reference frame in which the motion is defined.

Specified by:

getMotionReferenceFrame in class CartesianOnePointPropagator

Returns:

The reference frame.

getEvaluator

public MotionEvaluator1<Cartesian> getEvaluator(EvaluatorGroup group)

Gets an evaluator that can propagate at individual dates.

This evaluator propagates the orbit state from a collection of IGpsElements derived from a RinexNavigationRecord and based on the IS-GPS-200D standards. The result of evaluating will be a Motion<Cartesian> corresponding to the orbital position and velocity at the given JulianDate expressed in the Earth Fixed ReferenceFrame defined by the propagator.

Specified by:

getEvaluator in class CartesianOnePointPropagator

Parameters:

group - The group with which to associate the new evaluator. By grouping evaluators that are often evaluated at the same Julian dates, common computations can be performed only once for the entire group instead of multiple times for each evaluator.

Returns:

The evaluator.

See Also:

CartesianOnePointPropagator.createPoint()