private (PlanetPosition position, PlanetPosition speed) CalcBySegment(JulianDayNumber tjd, SEFileSegment segment, bool calcSpeed = true)
{
var t = (tjd - segment.Start).Raw / segment.Size.Raw;
t = t * 2 - 1;
var position = new PlanetPosition(
longitude: echeb(t, segment.LongitudeCoefficients),
latitude: echeb(t, segment.LatitudeCoefficients),
distance: echeb(t, segment.DistanceCoefficients)
);
PlanetPosition speed = default;
if (calcSpeed)
{
speed = new PlanetPosition(
longitude: edcheb(t, segment.LongitudeCoefficients),
latitude: edcheb(t, segment.LatitudeCoefficients),
distance: edcheb(t, segment.DistanceCoefficients)
);
}
return(position, speed);
}
/// <see cref="sweph"/>
private (PlanetPosition position, PlanetPosition speed) CalcBodyPositionAndSpeedInternal(int bodyNumber, DateTime dateTimeInUTC, bool calcSpeed)
{
var tjd = JulianDayNumber.FromDate(dateTimeInUTC);
var file = _storage.GetFile(bodyNumber, tjd);
var planet = bodyNumber > SEConsts.AseroidOffset
? InternalPlanets.AnyBody
: (InternalPlanets)bodyNumber;
var planetData = file.PlanetsData[planet];
var segment = file.ReadSegment(planetData, tjd, _sweData.oec2000);
var(position, speed) = CalcBySegment(tjd, segment, calcSpeed);
/* if planet wanted is barycentric sun:
* current sepl* files have do not have barycentric sun,
* but have heliocentric earth and barycentric earth.
* So barycentric sun and must be computed
* from heliocentric earth and barycentric earth: the
* computation above gives heliocentric earth, therefore we
* have to compute barycentric earth and subtract heliocentric
* earth from it. this may be necessary with calls from
* sweplan() and from app_pos_etc_sun() (light-time). */
if (bodyNumber == (int)InternalPlanets.BarycentricSun && planetData.Flags.HasFlag(PlanetFlags.EmbHeliocentric))
{
// sweph() calls sweph() !!! for EMB.
// because we always call new calculation, warning about EARTH and EMB equality was omitted
var(embPos, embSpeed) = CalcBodyPositionAndSpeedInternal((int)InternalPlanets.EMB, dateTimeInUTC, calcSpeed);
position = new PlanetPosition(
embPos.Longitude - position.Longitude,
embPos.Latitude - position.Latitude,
embPos.Distance - position.Distance);
if (calcSpeed)
{
speed = new PlanetPosition(
embSpeed.Longitude - speed.Longitude,
embSpeed.Latitude - speed.Latitude,
embSpeed.Distance - speed.Distance);
}
}
// asteroids are heliocentric.
// if JPL or SWISSEPH, convert to barycentric - currently always
if (planet >= InternalPlanets.AnyBody)
{
(position, speed) = ConvertToBarycentric(position, speed, dateTimeInUTC, calcSpeed);
}
return(position, speed);
}
public (PlanetPosition position, PlanetPosition speed) ConvertToBarycentric(
PlanetPosition position, PlanetPosition speed, DateTime dateTimeInUTC, bool calcSpeed)
{
// warning: in original code this value cached
var(sunPos, sunSpeed) = CalcBodyPositionAndSpeedInternal((int)InternalPlanets.BarycentricSun, dateTimeInUTC, calcSpeed);
position = new PlanetPosition(
sunPos.Longitude + position.Longitude,
sunPos.Latitude + position.Latitude,
sunPos.Distance + position.Distance);
if (calcSpeed)
{
speed = new PlanetPosition(
sunSpeed.Longitude + speed.Longitude,
sunSpeed.Latitude + speed.Latitude,
sunSpeed.Distance + speed.Distance);
}
return(position, speed);
}
/* Adjust position from Earth-Moon barycenter to Earth
*
* xemb = hel./bar. position or velocity vectors of emb (input)
* earth (output)
* xmoon= geocentric position or velocity vector of moon
*/
private static PlanetPosition embofs(PlanetPosition xemb, PlanetPosition xmoon)
{
