Examples with CachedNormalizedSphericalHarmonicsProvider org.orekit.forces.gravity.potential.CachedNormalizedSphericalHarmonicsProvider used on opensource projects

Example 1 with CachedNormalizedSphericalHarmonicsProvider

use of org.orekit.forces.gravity.potential.CachedNormalizedSphericalHarmonicsProvider in project Orekit by CS-SI.

the class SolidTidesFieldTest method testInterpolationAccuracy.

@Test
public void testInterpolationAccuracy() throws OrekitException {
    // The shortest periods are slightly below one half day for the tidal waves
    // considered here. This implies the sampling rate should be fast enough.
    // The tuning parameters we have finally settled correspond to a two hours
    // sample containing 12 points (i.e. one new point is computed every 10 minutes).
    // The observed relative interpolation error with these settings are essentially
    // due to Runge phenomenon at points sampling rate. Plotting the errors shows
    // singular peaks pointing out of merely numerical noise.
    final IERSConventions conventions = IERSConventions.IERS_2010;
    Frame itrf = FramesFactory.getITRF(conventions, true);
    TimeScale utc = TimeScalesFactory.getUTC();
    UT1Scale ut1 = TimeScalesFactory.getUT1(conventions, true);
    NormalizedSphericalHarmonicsProvider gravityField = GravityFieldFactory.getConstantNormalizedProvider(5, 5);
    SolidTidesField raw = new SolidTidesField(conventions.getLoveNumbers(), conventions.getTideFrequencyDependenceFunction(ut1), conventions.getPermanentTide(), conventions.getSolidPoleTide(ut1.getEOPHistory()), itrf, gravityField.getAe(), gravityField.getMu(), gravityField.getTideSystem(), CelestialBodyFactory.getSun(), CelestialBodyFactory.getMoon());
    int step = 600;
    int nbPoints = 12;
    CachedNormalizedSphericalHarmonicsProvider interpolated = new CachedNormalizedSphericalHarmonicsProvider(raw, step, nbPoints, OrekitConfiguration.getCacheSlotsNumber(), 7 * Constants.JULIAN_DAY, 0.5 * Constants.JULIAN_DAY);
    // the following time range is located around the maximal observed error
    AbsoluteDate start = new AbsoluteDate(2003, 6, 12, utc);
    AbsoluteDate end = start.shiftedBy(3 * Constants.JULIAN_DAY);
    StreamingStatistics stat = new StreamingStatistics();
    for (AbsoluteDate date = start; date.compareTo(end) < 0; date = date.shiftedBy(60)) {
        NormalizedSphericalHarmonics rawHarmonics = raw.onDate(date);
        NormalizedSphericalHarmonics interpolatedHarmonics = interpolated.onDate(date);
        for (int n = 2; n < 5; ++n) {
            for (int m = 0; m <= n; ++m) {
                if (n < 4 || m < 3) {
                    double cnmRaw = rawHarmonics.getNormalizedCnm(n, m);
                    double cnmInterp = interpolatedHarmonics.getNormalizedCnm(n, m);
                    double errorC = (cnmInterp - cnmRaw) / FastMath.abs(cnmRaw);
                    stat.addValue(errorC);
                    if (m > 0) {
                        double snmRaw = rawHarmonics.getNormalizedSnm(n, m);
                        double snmInterp = interpolatedHarmonics.getNormalizedSnm(n, m);
                        double errorS = (snmInterp - snmRaw) / FastMath.abs(snmRaw);
                        stat.addValue(errorS);
                    }
                }
            }
        }
    }
    Assert.assertEquals(0.0, stat.getMean(), 2.0e-12);
    Assert.assertTrue(stat.getStandardDeviation() < 2.0e-9);
    Assert.assertTrue(stat.getMin() > -9.0e-8);
    Assert.assertTrue(stat.getMax() < 2.2e-7);
}