AbstractGNSSAttitudeProvider.java
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* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
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package org.orekit.gnss.attitude;
import java.util.HashMap;
import java.util.Map;
import java.util.SortedSet;
import java.util.TreeSet;
import org.hipparchus.Field;
import org.hipparchus.CalculusFieldElement;
import org.orekit.attitudes.Attitude;
import org.orekit.attitudes.FieldAttitude;
import org.orekit.frames.Frame;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.ChronologicalComparator;
import org.orekit.time.FieldAbsoluteDate;
import org.orekit.time.TimeStamped;
import org.orekit.utils.ExtendedPVCoordinatesProvider;
import org.orekit.utils.FieldPVCoordinatesProvider;
import org.orekit.utils.PVCoordinatesProvider;
import org.orekit.utils.TimeStampedAngularCoordinates;
import org.orekit.utils.TimeStampedFieldAngularCoordinates;
/**
* Base class for attitude providers for navigation satellites.
*
* @author Luc Maisonobe
* @since 9.2
*/
abstract class AbstractGNSSAttitudeProvider implements GNSSAttitudeProvider {
/** Start of validity for this provider. */
private final AbsoluteDate validityStart;
/** End of validity for this provider. */
private final AbsoluteDate validityEnd;
/** Provider for Sun position. */
private final ExtendedPVCoordinatesProvider sun;
/** Inertial frame where velocity are computed. */
private final Frame inertialFrame;
/** Turns already encountered. */
private final SortedSet<TimeStamped> turns;
/** Turns already encountered. */
private final transient Map<Field<? extends CalculusFieldElement<?>>, SortedSet<TimeStamped>> fieldTurns;
/** Simple constructor.
* @param validityStart start of validity for this provider
* @param validityEnd end of validity for this provider
* @param sun provider for Sun position
* @param inertialFrame inertial frame where velocity are computed
*/
protected AbstractGNSSAttitudeProvider(final AbsoluteDate validityStart,
final AbsoluteDate validityEnd,
final ExtendedPVCoordinatesProvider sun,
final Frame inertialFrame) {
this.validityStart = validityStart;
this.validityEnd = validityEnd;
this.sun = sun;
this.inertialFrame = inertialFrame;
this.turns = new TreeSet<>(new ChronologicalComparator());
this.fieldTurns = new HashMap<>();
}
/** {@inheritDoc} */
@Override
public AbsoluteDate validityStart() {
return validityStart;
}
/** {@inheritDoc} */
@Override
public AbsoluteDate validityEnd() {
return validityEnd;
}
/** {@inheritDoc} */
@Override
public Attitude getAttitude(final PVCoordinatesProvider pvProv,
final AbsoluteDate date,
final Frame frame) {
// compute yaw correction
final TurnSpan turnSpan = getTurnSpan(date);
final GNSSAttitudeContext context = new GNSSAttitudeContext(date, sun, pvProv, inertialFrame, turnSpan);
final TimeStampedAngularCoordinates corrected = correctedYaw(context);
if (turnSpan == null && context.getTurnSpan() != null) {
// we have encountered a new turn, store it
turns.add(context.getTurnSpan());
}
return new Attitude(inertialFrame, corrected).withReferenceFrame(frame);
}
/** {@inheritDoc} */
@Override
public <T extends CalculusFieldElement<T>> FieldAttitude<T> getAttitude(final FieldPVCoordinatesProvider<T> pvProv,
final FieldAbsoluteDate<T> date,
final Frame frame) {
// compute yaw correction
final FieldTurnSpan<T> turnSpan = getTurnSpan(date);
final GNSSFieldAttitudeContext<T> context = new GNSSFieldAttitudeContext<>(date, sun, pvProv, inertialFrame, turnSpan);
final TimeStampedFieldAngularCoordinates<T> corrected = correctedYaw(context);
if (turnSpan == null && context.getTurnSpan() != null) {
// we have encountered a new turn, store it
fieldTurns.get(date.getField()).add(context.getTurnSpan());
}
return new FieldAttitude<>(inertialFrame, corrected).withReferenceFrame(frame);
}
/** Get the turn span covering a date.
* @param date date to check
* @return turn span covering the date, or null if no span covers this date
*/
private TurnSpan getTurnSpan(final AbsoluteDate date) {
// as the reference date of the turn span is the end + margin date,
// the span to consider can only be the first span that is after date
final SortedSet<TimeStamped> after = turns.tailSet(date);
if (!after.isEmpty()) {
final TurnSpan ts = (TurnSpan) after.first();
if (ts.inTurnTimeRange(date)) {
return ts;
}
}
// no turn covers the date
return null;
}
/** Get the turn span covering a date.
* @param date date to check
* @param <T> type of the field elements
* @return turn span covering the date, or null if no span covers this date
*/
private <T extends CalculusFieldElement<T>> FieldTurnSpan<T> getTurnSpan(final FieldAbsoluteDate<T> date) {
SortedSet<TimeStamped> sortedSet = fieldTurns.get(date.getField());
if (sortedSet == null) {
// this is the first time we manage such a field, prepare a sorted set for it
sortedSet = new TreeSet<>(new ChronologicalComparator());
fieldTurns.put(date.getField(), sortedSet);
}
// as the reference date of the turn span is the end + margin date,
// the span to consider can only be the first span that is after date
final AbsoluteDate dateDouble = date.toAbsoluteDate();
final SortedSet<TimeStamped> after = sortedSet.tailSet(dateDouble);
if (!after.isEmpty()) {
@SuppressWarnings("unchecked")
final FieldTurnSpan<T> ts = (FieldTurnSpan<T>) after.first();
if (ts.inTurnTimeRange(dateDouble)) {
return ts;
}
}
// no turn covers the date
return null;
}
/** Get provider for Sun position.
* @return provider for Sun position
* @since 12.0
*/
protected ExtendedPVCoordinatesProvider getSun() {
return sun;
}
/** Get inertial frame where velocity are computed.
* @return inertial frame where velocity are computed
*/
protected Frame getInertialFrame() {
return inertialFrame;
}
/** Select the
/** Compute GNSS attitude with midnight/noon yaw turn correction.
* @param context context data for attitude computation
* @return corrected yaw, using inertial frame as the reference
*/
protected abstract TimeStampedAngularCoordinates correctedYaw(GNSSAttitudeContext context);
/** Compute GNSS attitude with midnight/noon yaw turn correction.
* @param context context data for attitude computation
* @param <T> type of the field elements
* @return corrected yaw, using inertial frame as the reference
*/
protected abstract <T extends CalculusFieldElement<T>> TimeStampedFieldAngularCoordinates<T>
correctedYaw(GNSSFieldAttitudeContext<T> context);
}