/// <summary>
/// <see cref="swi_check_nutation"/>
/// </summary>
internal static Nutation Calculate(JulianDayNumber tjd, SweData swed)
{
var(longitude, obliquity) = swi_nutation(tjd, swed);
var matrix = nut_matrix(longitude, obliquity, swed.oec);
return(new Nutation(tjd, longitude, obliquity, matrix));
}
private static (double longitude, double obliquity) swi_nutation(JulianDayNumber tjd, SweData swed)
{
// from interpolation, with three data points in 1-day steps;
// maximum error is about 3 mas
if (swed.InterpolateNutation)
{
// precalculated data points available
if (swed.InterpolatedNutation != null && tjd < swed.InterpolatedNutation.Time2 && tjd > swed.InterpolatedNutation.Time0)
{
var dx = (tjd - swed.InterpolatedNutation.Time0).Raw - 1.0;
var longitude = quadratic_intp(swed.InterpolatedNutation.DPsi0, swed.InterpolatedNutation.DPsi1, swed.InterpolatedNutation.DPsi2, dx);
var obliquity = quadratic_intp(swed.InterpolatedNutation.DEps0, swed.InterpolatedNutation.DEps1, swed.InterpolatedNutation.DEps2, dx);
return(longitude, obliquity);
}
else
{
var interpol = new InterpolatedNutation
{
Time0 = tjd.AddDays(-1.0), // one day earlier
Time2 = tjd.AddDays(1.0) // one day later
};
(interpol.DPsi0, interpol.DEps0) = calc_nutation(interpol.Time0, swed);
(interpol.DPsi2, interpol.DEps2) = calc_nutation(interpol.Time2, swed);
(interpol.DPsi1, interpol.DEps1) = calc_nutation(tjd, swed);
swed.InterpolatedNutation = interpol;
return(interpol.DPsi1, interpol.DEps1);
}
}
return(calc_nutation(tjd, swed));
}
internal static Nutation CalculateForSpeed(JulianDayNumber tjd, SweData swed) => Calculate(tjd.AddDays(-NUT_SPEED_INTV), swed);
private static (double longitude, double obliquity) calc_nutation(JulianDayNumber J, SweData swed)
{
int n;
double dpsi, deps;
double longitude = 0.0, obliquity = 0.0;
var jplhora_model = swed.JplHorizonsMode;
var nut_model = swed.NutationModel;
bool is_jplhor = false;
if (swed.Iflag.HasFlag(SEFLG.JPLHOR))
{
is_jplhor = true;
}
if (swed.Iflag.HasFlag(SEFLG.JPLHOR_APPROX) &&
jplhora_model == JplHorizonsMode.Three &&
J <= HORIZONS_TJD0_DPSI_DEPS_IAU1980)
{
is_jplhor = true;
}
if (is_jplhor)
{
(longitude, obliquity) = calc_nutation_iau1980(J, nut_model);
if (swed.Iflag.HasFlag(SEFLG.JPLHOR))
{
n = (int)(swed.Eop.EndDate.Raw - swed.Eop.BeginDate.Raw + 0.000001);
var J2 = J;
if (J < DPSI_DEPS_IAU1980_TJD0_HORIZONS)
{
J2 = DPSI_DEPS_IAU1980_TJD0_HORIZONS;
}
var t = (J2 - swed.Eop.BeginDate).Raw;
dpsi = bessel(swed.Eop.dPsi, n + 1, t);
deps = bessel(swed.Eop.dEps, n + 1, t);
longitude += dpsi / 3600.0 * DEGTORAD;
obliquity += deps / 3600.0 * DEGTORAD;
}
else
{
longitude += DPSI_IAU1980_TJD0 / 3600.0 * DEGTORAD;
obliquity += DEPS_IAU1980_TJD0 / 3600.0 * DEGTORAD;
}
}
else if (nut_model == NutationModel.IAU_1980 || nut_model == NutationModel.IAU_CORR_1987)
{
(longitude, obliquity) = calc_nutation_iau1980(J, nut_model);
}
else if (nut_model == NutationModel.IAU_2000A || nut_model == NutationModel.IAU_2000B)
{
(longitude, obliquity) = calc_nutation_iau2000ab(J, nut_model);
if (swed.Iflag.HasFlag(SEFLG.JPLHOR_APPROX) && jplhora_model == JplHorizonsMode.Two)
{
longitude += -41.7750 / 3600.0 / 1000.0 * DEGTORAD;
obliquity += -6.8192 / 3600.0 / 1000.0 * DEGTORAD;
}
}
return(longitude, obliquity);
}
public PositionCalculatorInternal(SweData sweData, SwephFilesStorage storage)
{
_sweData = sweData;
_swephFiles = storage;
}
public SwePositionCalculator(SweData sweData, SwephFilesStorage storage)
{
_sweData = sweData;
_storage = storage;
}
