Examples with FieldBracketingNthOrderBrentSolver org.hipparchus.analysis.solvers.FieldBracketingNthOrderBrentSolver used on opensource projects

Example 1 with FieldBracketingNthOrderBrentSolver

use of org.hipparchus.analysis.solvers.FieldBracketingNthOrderBrentSolver 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;
    }
}