Examples with FieldAbsoluteDate org.orekit.time.FieldAbsoluteDate used on opensource projects

Example 16 with FieldAbsoluteDate

use of org.orekit.time.FieldAbsoluteDate in project Orekit by CS-SI.

the class FieldEventState method findRoot.

/**
 * Find a root in a bracketing interval.
 *
 * <p> When calling this method one of the following must be true. Either ga == 0, gb
 * == 0, (ga < 0  and gb > 0), or (ga > 0 and gb < 0).
 *
 * @param interpolator that covers the interval.
 * @param ta           earliest possible time for root.
 * @param ga           g(ta).
 * @param tb           latest possible time for root.
 * @param gb           g(tb).
 * @return if a zero crossing was found.
 * @throws OrekitException if the event detector throws one
 */
private boolean findRoot(final FieldOrekitStepInterpolator<T> interpolator, final FieldAbsoluteDate<T> ta, final T ga, final FieldAbsoluteDate<T> tb, final T gb) throws OrekitException {
    final T zero = ga.getField().getZero();
    // check there appears to be a root in [ta, tb]
    check(ga.getReal() == 0.0 || gb.getReal() == 0.0 || (ga.getReal() > 0.0 && gb.getReal() < 0.0) || (ga.getReal() < 0.0 && gb.getReal() > 0.0));
    final T convergence = detector.getThreshold();
    final int maxIterationCount = detector.getMaxIterationCount();
    final BracketedUnivariateSolver<UnivariateFunction> solver = new BracketingNthOrderBrentSolver(0, convergence.getReal(), 0, 5);
    // event time, just at or before the actual root.
    FieldAbsoluteDate<T> beforeRootT = null;
    T beforeRootG = zero.add(Double.NaN);
    // time on the other side of the root.
    // Initialized the the loop below executes once.
    FieldAbsoluteDate<T> afterRootT = ta;
    T afterRootG = zero;
    // the ga == 0.0 case is handled by the loop below
    if (ta.equals(tb)) {
        // both non-zero but times are the same. Probably due to reset state
        beforeRootT = ta;
        beforeRootG = ga;
        afterRootT = shiftedBy(beforeRootT, convergence);
        afterRootG = g(interpolator.getInterpolatedState(afterRootT));
    } else if (ga.getReal() != 0.0 && gb.getReal() == 0.0) {
        // hard: ga != 0.0 and gb == 0.0
        // look past gb by up to convergence to find next sign
        // throw an exception if g(t) = 0.0 in [tb, tb + convergence]
        beforeRootT = tb;
        beforeRootG = gb;
        afterRootT = shiftedBy(beforeRootT, convergence);
        afterRootG = g(interpolator.getInterpolatedState(afterRootT));
    } else if (ga.getReal() != 0.0) {
        final T newGa = g(interpolator.getInterpolatedState(ta));
        if (ga.getReal() > 0 != newGa.getReal() > 0) {
            // both non-zero, step sign change at ta, possibly due to reset state
            beforeRootT = ta;
            beforeRootG = newGa;
            afterRootT = minTime(shiftedBy(beforeRootT, convergence), tb);
            afterRootG = g(interpolator.getInterpolatedState(afterRootT));
        }
    }
    // loop to skip through "fake" roots, i.e. where g(t) = g'(t) = 0.0
    // executed once if we didn't hit a special case above
    FieldAbsoluteDate<T> loopT = ta;
    T loopG = ga;
    while ((afterRootG.getReal() == 0.0 || afterRootG.getReal() > 0.0 == g0Positive) && strictlyAfter(afterRootT, tb)) {
        if (loopG.getReal() == 0.0) {
            // ga == 0.0 and gb may or may not be 0.0
            // handle the root at ta first
            beforeRootT = loopT;
            beforeRootG = loopG;
            afterRootT = minTime(shiftedBy(beforeRootT, convergence), tb);
            afterRootG = g(interpolator.getInterpolatedState(afterRootT));
        } else {
            // both non-zero, the usual case, use a root finder.
            try {
                // time zero for evaluating the function f. Needs to be final
                final FieldAbsoluteDate<T> fT0 = loopT;
                final UnivariateFunction f = dt -> {
                    try {
                        return g(interpolator.getInterpolatedState(fT0.shiftedBy(dt))).getReal();
                    } catch (OrekitException oe) {
                        throw new OrekitExceptionWrapper(oe);
                    }
                };
                // tb as a double for use in f
                final T tbDouble = tb.durationFrom(fT0);
                if (forward) {
                    final Interval interval = solver.solveInterval(maxIterationCount, f, 0, tbDouble.getReal());
                    beforeRootT = fT0.shiftedBy(interval.getLeftAbscissa());
                    beforeRootG = zero.add(interval.getLeftValue());
                    afterRootT = fT0.shiftedBy(interval.getRightAbscissa());
                    afterRootG = zero.add(interval.getRightValue());
                } else {
                    final Interval interval = solver.solveInterval(maxIterationCount, f, tbDouble.getReal(), 0);
                    beforeRootT = fT0.shiftedBy(interval.getRightAbscissa());
                    beforeRootG = zero.add(interval.getRightValue());
                    afterRootT = fT0.shiftedBy(interval.getLeftAbscissa());
                    afterRootG = zero.add(interval.getLeftValue());
                }
            } catch (OrekitExceptionWrapper oew) {
                throw oew.getException();
            }
        }
        // assume tolerance is 1 ulp
        if (beforeRootT.equals(afterRootT)) {
            afterRootT = nextAfter(afterRootT);
            afterRootG = g(interpolator.getInterpolatedState(afterRootT));
        }
        // check loop is making some progress
        check((forward && afterRootT.compareTo(beforeRootT) > 0) || (!forward && afterRootT.compareTo(beforeRootT) < 0));
        // setup next iteration
        loopT = afterRootT;
        loopG = afterRootG;
    }
    // figure out the result of root finding, and return accordingly
    if (afterRootG.getReal() == 0.0 || afterRootG.getReal() > 0.0 == g0Positive) {
        // loop gave up and didn't find any crossing within this step
        return false;
    } else {
        // real crossing
        check(beforeRootT != null && !Double.isNaN(beforeRootG.getReal()));
        // variation direction, with respect to the integration direction
        increasing = !g0Positive;
        pendingEventTime = beforeRootT;
        stopTime = beforeRootG.getReal() == 0.0 ? beforeRootT : afterRootT;
        pendingEvent = true;
        afterEvent = afterRootT;
        afterG = afterRootG;
        // check increasing set correctly
        check(afterG.getReal() > 0 == increasing);
        check(increasing == gb.getReal() >= ga.getReal());
        return true;
    }
}

Example 17 with FieldAbsoluteDate

use of org.orekit.time.FieldAbsoluteDate in project Orekit by CS-SI.

the class Geoid method getIntersectionPoint.

/**
 * {@inheritDoc}
 *
 * <p> The intersection point is computed using a line search along the
 * specified line. This is accurate when the geoid is slowly varying.
 */
@Override
public <T extends RealFieldElement<T>> FieldGeodeticPoint<T> getIntersectionPoint(final FieldLine<T> lineInFrame, final FieldVector3D<T> closeInFrame, final Frame frame, final FieldAbsoluteDate<T> date) throws OrekitException {
    final Field<T> field = date.getField();
    /*
         * It is assumed that the geoid is slowly varying over it's entire
         * surface. Therefore there will one local intersection.
         */
    // transform to body frame
    final Frame bodyFrame = this.getBodyFrame();
    final FieldTransform<T> frameToBody = frame.getTransformTo(bodyFrame, date);
    final FieldVector3D<T> close = frameToBody.transformPosition(closeInFrame);
    final FieldLine<T> lineInBodyFrame = frameToBody.transformLine(lineInFrame);
    // set the line's direction so the solved for value is always positive
    final FieldLine<T> line;
    if (lineInBodyFrame.getAbscissa(close).getReal() < 0) {
        line = lineInBodyFrame.revert();
    } else {
        line = lineInBodyFrame;
    }
    final ReferenceEllipsoid ellipsoid = this.getEllipsoid();
    // calculate end points
    // distance from line to center of earth, squared
    final T d2 = line.pointAt(0.0).getNormSq();
    // the minimum abscissa, squared
    final double n = ellipsoid.getPolarRadius() + MIN_UNDULATION;
    final T minAbscissa2 = d2.negate().add(n * n);
    // smaller end point of the interval = 0.0 or intersection with
    // min_undulation sphere
    final T lowPoint = minAbscissa2.getReal() < 0 ? field.getZero() : minAbscissa2.sqrt();
    // the maximum abscissa, squared
    final double x = ellipsoid.getEquatorialRadius() + MAX_UNDULATION;
    final T maxAbscissa2 = d2.negate().add(x * x);
    // larger end point of the interval
    final T highPoint = maxAbscissa2.sqrt();
    // line search function
    final RealFieldUnivariateFunction<T> heightFunction = z -> {
        try {
            final FieldGeodeticPoint<T> geodetic = transform(line.pointAt(z), bodyFrame, date);
            return geodetic.getAltitude();
        } catch (OrekitException e) {
            // due to frame transform -> re-throw
            throw new RuntimeException(e);
        }
    };
    // compute answer
    if (maxAbscissa2.getReal() < 0) {
        // ray does not pierce bounding sphere -> no possible intersection
        return null;
    }
    // solve line search problem to find the intersection
    final FieldBracketingNthOrderBrentSolver<T> solver = new FieldBracketingNthOrderBrentSolver<>(field.getZero().add(1.0e-14), field.getZero().add(1.0e-6), field.getZero().add(1.0e-15), 5);
    try {
        final T abscissa = solver.solve(MAX_EVALUATIONS, heightFunction, lowPoint, highPoint, AllowedSolution.ANY_SIDE);
        // return intersection point
        return this.transform(line.pointAt(abscissa), bodyFrame, date);
    } catch (MathRuntimeException e) {
        // no intersection
        return null;
    }
}

Example 18 with FieldAbsoluteDate

use of org.orekit.time.FieldAbsoluteDate in project Orekit by CS-SI.

the class EOPHistory method interpolate.

/**
 * Interpolate a single EOP component.
 * <p>
 * This method should be called <em>only</em> when {@link #hasDataFor(AbsoluteDate)} returns true.
 * </p>
 * @param date interpolation date
 * @param aDate interpolation date, as an {@link AbsoluteDate}
 * @param selector selector for EOP entry component
 * @param <T> type of the field elements
 * @return interpolated value
 */
private <T extends RealFieldElement<T>> T interpolate(final FieldAbsoluteDate<T> date, final AbsoluteDate aDate, final Function<EOPEntry, Double> selector) {
    try {
        final FieldHermiteInterpolator<T> interpolator = new FieldHermiteInterpolator<>();
        final T[] y = MathArrays.buildArray(date.getField(), 1);
        final T zero = date.getField().getZero();
        // here, we attempt to get a constant date,
        final FieldAbsoluteDate<T> central = new FieldAbsoluteDate<>(aDate, zero);
        // for example removing derivatives
        // if T was DerivativeStructure
        getNeighbors(aDate).forEach(entry -> {
            y[0] = zero.add(selector.apply(entry));
            interpolator.addSamplePoint(central.durationFrom(entry.getDate()).negate(), y);
        });
        // here, we introduce derivatives again (in DerivativeStructure case)
        return interpolator.value(date.durationFrom(central))[0];
    } catch (TimeStampedCacheException tce) {
        // this should not happen because of date check performed by caller
        throw new OrekitInternalError(tce);
    }
}

Example 19 with FieldAbsoluteDate

use of org.orekit.time.FieldAbsoluteDate in project Orekit by CS-SI.

the class EOPHistory method getPoleCorrection.

/**
 * Get the pole IERS Reference Pole correction.
 * <p>The data provided comes from the IERS files. It is smoothed data.</p>
 * @param date date at which the correction is desired
 * @param <T> type of the field elements
 * @return pole correction ({@link PoleCorrection#NULL_CORRECTION
 * PoleCorrection.NULL_CORRECTION} if date is outside covered range)
 */
public <T extends RealFieldElement<T>> FieldPoleCorrection<T> getPoleCorrection(final FieldAbsoluteDate<T> date) {
    final AbsoluteDate aDate = date.toAbsoluteDate();
    // check if there is data for date
    if (!this.hasDataFor(aDate)) {
        // no EOP data available for this date, we use a default null correction
        if (tidalCorrection == null) {
            return new FieldPoleCorrection<>(date.getField().getZero(), date.getField().getZero());
        } else {
            final T[] correction = tidalCorrection.value(date);
            return new FieldPoleCorrection<>(correction[0], correction[1]);
        }
    }
    // we have EOP data for date -> interpolate correction
    final T[] interpolated = interpolate(date, aDate, entry -> entry.getX(), entry -> entry.getY());
    if (tidalCorrection != null) {
        final T[] correction = tidalCorrection.value(date);
        interpolated[0] = interpolated[0].add(correction[0]);
        interpolated[1] = interpolated[1].add(correction[1]);
    }
    return new FieldPoleCorrection<>(interpolated[0], interpolated[1]);
}

Example 20 with FieldAbsoluteDate

use of org.orekit.time.FieldAbsoluteDate in project Orekit by CS-SI.

the class EOPHistory method getLOD.

/**
 * Get the LoD (Length of Day) value.
 * <p>The data provided comes from the IERS files. It is smoothed data.</p>
 * @param date date at which the value is desired
 * @param <T> type of the filed elements
 * @return LoD in seconds (0 if date is outside covered range)
 * @since 9.0
 */
public <T extends RealFieldElement<T>> T getLOD(final FieldAbsoluteDate<T> date) {
    final AbsoluteDate aDate = date.toAbsoluteDate();
    // check if there is data for date
    if (!this.hasDataFor(aDate)) {
        // no EOP data available for this date, we use a default null correction
        return (tidalCorrection == null) ? date.getField().getZero() : tidalCorrection.value(date)[3];
    }
    // we have EOP data for date -> interpolate correction
    T interpolated = interpolate(date, aDate, entry -> entry.getLOD());
    if (tidalCorrection != null) {
        interpolated = interpolated.add(tidalCorrection.value(date)[3]);
    }
    return interpolated;
}