Coordinate Transformations¶

The astrojax.coordinates module provides functions for converting between the coordinate representations commonly used in astrodynamics.

Coordinate Systems¶

System	Format	Description
ECEF	`[x, y, z]` metres	Earth-Centered Earth-Fixed Cartesian
Geocentric	`[lon, lat, alt]`	Spherical Earth model (radius = WGS84 semi-major axis)
Geodetic	`[lon, lat, alt]`	WGS84 ellipsoid model (accounts for Earth's oblateness)
Keplerian	`[a, e, i, Ω, ω, M]`	Classical orbital elements
ENZ	`[east, north, zenith]` metres	Local topocentric frame at an observer station

JAX Compatibility¶

All coordinate functions are compatible with jax.jit and jax.vmap:

import jax
import jax.numpy as jnp
from astrojax.constants import R_EARTH
from astrojax.coordinates import (
    relative_position_ecef_to_enz,
    position_enz_to_azel,
)

x_sta = jnp.array([R_EARTH, 0.0, 0.0])

# JIT-compiled ENZ conversion
jit_enz = jax.jit(
    lambda r: relative_position_ecef_to_enz(x_sta, r, use_geodetic=False)
)
x_sat = jnp.array([R_EARTH + 500e3, 0.0, 0.0])
r_enz = jit_enz(x_sat)

# Batch azimuth/elevation over multiple ENZ positions
enz_batch = jnp.array([
    [0.0, 0.0, 100.0],
    [100.0, 0.0, 0.0],
    [0.0, 100.0, 0.0],
])
azels = jax.vmap(position_enz_to_azel)(enz_batch)

float32 precision

ENZ roundtrip transformations (ECEF → ENZ → ECEF) are accurate to ~1 m in position with the default float32 precision.