Module pymap3d.eci
transforms involving ECI earth-centered inertial
Source code
""" transforms involving ECI earth-centered inertial """
from datetime import datetime
import numpy as np
from typing import Tuple
from .sidereal import datetime2sidereal
try:
from astropy.time import Time
except ImportError:
Time = None
__all__ = ["eci2ecef", "ecef2eci"]
def eci2ecef(x: float, y: float, z: float = None, time: datetime = None, *, useastropy: bool = True) -> Tuple[float, float, float]:
"""
Observer => Point ECI => ECEF
defaults to J2000 frame
Parameters
----------
x : float
ECI x-location [meters]
y : float
ECI y-location [meters]
z : float
ECI z-location [meters]
time : datetime.datetime
time of obsevation (UTC)
useastropy : bool, optional
use AstroPy for conversion
Results
-------
x : float
target x ECEF coordinate
y : float
target y ECEF coordinate
z : float
target z ECEF coordinate
"""
# %%
x = np.atleast_1d(x)
y = np.atleast_1d(y)
z = np.atleast_1d(z)
if not x.shape == y.shape == z.shape:
raise ValueError("shapes of ECI x,y,z must be identical")
useastropy = useastropy and Time is not None
if useastropy:
gst = Time(time).sidereal_time("apparent", "greenwich").radian
else:
gst = datetime2sidereal(time, 0.0)
gst = np.atleast_1d(gst)
if gst.ndim != 1 or not isinstance(gst[0], float):
raise ValueError("GST must be vector in radians")
if gst.size == 1:
gst *= np.ones(x.size)
if gst.size != x.size:
raise ValueError("GST must be scalar or same length as positions")
eci = np.column_stack((x.ravel(), y.ravel(), z.ravel()))
ecef = np.empty((x.size, 3))
for i in range(eci.shape[0]):
ecef[i, :] = _rottrip(gst[i]) @ eci[i, :]
xecef = ecef[:, 0].reshape(x.shape)
yecef = ecef[:, 1].reshape(x.shape)
zecef = ecef[:, 2].reshape(x.shape)
return xecef, yecef, zecef
def ecef2eci(x: float, y: float, z: float = None, time: datetime = None, *, useastropy: bool = True) -> Tuple[float, float, float]:
"""
Point => Point ECEF => ECI
Parameters
----------
x : float
target x ECEF coordinate
y : float
target y ECEF coordinate
z : float
target z ECEF coordinate
time : datetime.datetime
time of observation
useastropy : bool, optional
use AstroPy for conversion
Results
-------
x : float
target x ECI coordinate
y : float
target y ECI coordinate
z : float
target z ECI coordinate
"""
# %%
x = np.atleast_1d(x)
y = np.atleast_1d(y)
z = np.atleast_1d(z)
if not x.shape == y.shape == z.shape:
raise ValueError("shapes of ECI x,y,z must be identical")
useastropy = useastropy and Time is not None
if useastropy:
gst = Time(time).sidereal_time("apparent", "greenwich").radian
else:
gst = datetime2sidereal(time, 0.0)
gst = np.atleast_1d(gst)
if gst.ndim != 1 or not isinstance(gst[0], float):
raise ValueError("GST must be vector in radians")
if gst.size == 1:
gst *= np.ones(x.size)
if gst.size != x.size:
raise ValueError("GST must be scalar or same length as positions")
ecef = np.column_stack((x.ravel(), y.ravel(), z.ravel()))
eci = np.empty((x.size, 3))
for i in range(x.size):
eci[i, :] = _rottrip(gst[i]).T @ ecef[i, :] # this one is transposed
xeci = eci[:, 0].reshape(x.shape)
yeci = eci[:, 1].reshape(x.shape)
zeci = eci[:, 2].reshape(x.shape)
return xeci, yeci, zeci
def _rottrip(ang: float) -> np.ndarray:
"""
transformation matrix
Parameters
----------
ang : float
angle to transform (radians)
Returns
-------
T : numpy.ndarray of float
3 x 3 transformation matrix
"""
return np.array([[np.cos(ang), np.sin(ang), 0], [-np.sin(ang), np.cos(ang), 0], [0, 0, 1]])Functions
def ecef2eci(x, y, z=None, time=None, *, useastropy=True)-
Point => Point ECEF => ECI
Parameters
x:float- target x ECEF coordinate
y:float- target y ECEF coordinate
z:float- target z ECEF coordinate
time:datetime.datetime- time of observation
useastropy:bool, optional- use AstroPy for conversion
Results
x:float- target x ECI coordinate
y:float- target y ECI coordinate
z:float- target z ECI coordinate
Source code
def ecef2eci(x: float, y: float, z: float = None, time: datetime = None, *, useastropy: bool = True) -> Tuple[float, float, float]: """ Point => Point ECEF => ECI Parameters ---------- x : float target x ECEF coordinate y : float target y ECEF coordinate z : float target z ECEF coordinate time : datetime.datetime time of observation useastropy : bool, optional use AstroPy for conversion Results ------- x : float target x ECI coordinate y : float target y ECI coordinate z : float target z ECI coordinate """ # %% x = np.atleast_1d(x) y = np.atleast_1d(y) z = np.atleast_1d(z) if not x.shape == y.shape == z.shape: raise ValueError("shapes of ECI x,y,z must be identical") useastropy = useastropy and Time is not None if useastropy: gst = Time(time).sidereal_time("apparent", "greenwich").radian else: gst = datetime2sidereal(time, 0.0) gst = np.atleast_1d(gst) if gst.ndim != 1 or not isinstance(gst[0], float): raise ValueError("GST must be vector in radians") if gst.size == 1: gst *= np.ones(x.size) if gst.size != x.size: raise ValueError("GST must be scalar or same length as positions") ecef = np.column_stack((x.ravel(), y.ravel(), z.ravel())) eci = np.empty((x.size, 3)) for i in range(x.size): eci[i, :] = _rottrip(gst[i]).T @ ecef[i, :] # this one is transposed xeci = eci[:, 0].reshape(x.shape) yeci = eci[:, 1].reshape(x.shape) zeci = eci[:, 2].reshape(x.shape) return xeci, yeci, zeci def eci2ecef(x, y, z=None, time=None, *, useastropy=True)-
Observer => Point ECI => ECEF
defaults to J2000 frame
Parameters
x:float- ECI x-location [meters]
y:float- ECI y-location [meters]
z:float- ECI z-location [meters]
time:datetime.datetime- time of obsevation (UTC)
useastropy:bool, optional- use AstroPy for conversion
Results
x:float- target x ECEF coordinate
y:float- target y ECEF coordinate
z:float- target z ECEF coordinate
Source code
def eci2ecef(x: float, y: float, z: float = None, time: datetime = None, *, useastropy: bool = True) -> Tuple[float, float, float]: """ Observer => Point ECI => ECEF defaults to J2000 frame Parameters ---------- x : float ECI x-location [meters] y : float ECI y-location [meters] z : float ECI z-location [meters] time : datetime.datetime time of obsevation (UTC) useastropy : bool, optional use AstroPy for conversion Results ------- x : float target x ECEF coordinate y : float target y ECEF coordinate z : float target z ECEF coordinate """ # %% x = np.atleast_1d(x) y = np.atleast_1d(y) z = np.atleast_1d(z) if not x.shape == y.shape == z.shape: raise ValueError("shapes of ECI x,y,z must be identical") useastropy = useastropy and Time is not None if useastropy: gst = Time(time).sidereal_time("apparent", "greenwich").radian else: gst = datetime2sidereal(time, 0.0) gst = np.atleast_1d(gst) if gst.ndim != 1 or not isinstance(gst[0], float): raise ValueError("GST must be vector in radians") if gst.size == 1: gst *= np.ones(x.size) if gst.size != x.size: raise ValueError("GST must be scalar or same length as positions") eci = np.column_stack((x.ravel(), y.ravel(), z.ravel())) ecef = np.empty((x.size, 3)) for i in range(eci.shape[0]): ecef[i, :] = _rottrip(gst[i]) @ eci[i, :] xecef = ecef[:, 0].reshape(x.shape) yecef = ecef[:, 1].reshape(x.shape) zecef = ecef[:, 2].reshape(x.shape) return xecef, yecef, zecef