bodycentric_transforms.hpp File Reference

Body-centric coordinate transformations. More...

#include "../ffi_core.hpp"
#include "../orbital_center.hpp"
#include "../time.hpp"
#include "cartesian.hpp"
#include <cstdint>

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Classes
struct	siderust::BodycentricPos< F, U >
	Result of a body-centric coordinate transformation. More...

Namespaces
namespace	siderust

Functions
template<typename C , typename F , typename U >
BodycentricPos< F, U >	siderust::to_bodycentric (const cartesian::Position< C, F, U > &pos, const BodycentricParams &params, const Time< TT, JD > &jd)
	Transform a position to body-centric coordinates.

Detailed Description

Body-centric coordinate transformations.

Mirrors Rust's ToBodycentricExt and FromBodycentricExt traits:

• to_bodycentric(pos, params, jd) — free function transforming a Geocentric/Heliocentric/Barycentric position to one centered on the orbiting body described by params.
• BodycentricPos<F,U>::to_geocentric(jd) — inverse transform back to geocentric.

The transform algorithm (mirroring Rust):

1. Propagate the body's Keplerian orbit to JD → position in the orbit's reference center.
2. Convert that position to match the source center (via VSOP87 offsets).
3. bodycentric = input - body_in_source_center

Usage

#include <siderust/siderust.hpp>   // or just this file
using namespace siderust;
using namespace siderust::frames;
using namespace siderust::centers;
using qtty::AstronomicalUnit;
 
auto jd = Time<TT, JD>::J2000();
 
// ISS-like geocentric orbit
KeplerianOrbit iss_orbit{0.0000426_au, Eccentricity{0.001}, 51.6_deg,
                          0.0_deg, 0.0_deg, 0.0_deg, jd};
BodycentricParams iss_params = BodycentricParams::geocentric(iss_orbit);
 
// Moon's approximate geocentric position
cartesian::Position<Geocentric, EclipticMeanJ2000, AstronomicalUnit>
moon_geo( 0.00257, 0.0, 0.0);
 
// Moon as seen from ISS
auto moon_from_iss = to_bodycentric(moon_geo, iss_params, jd);
 
// Round-trip back to geocentric
auto recovered = moon_from_iss.to_geocentric(jd);

Definition in file bodycentric_transforms.hpp.