# (C) 2020 University of Colorado AES-CCAR-SEDA (Space Environment Data Analysis) Group
# Written by Liam M. Kilcommons
import numpy as np
from numpy import (cos,sin,tan,arccos,arcsin,arctan2)
from geospacepy.array_management import (CheckInputsAreThreeComponentVectors,
BroadcastLenOneInputsToMatchArrayInputs)
from geospacepy.rotations import rot1,rot2,rot3
from geospacepy.sun import greenwich_mean_siderial_time
from scipy.spatial.transform import Rotation
R_EARTH = 6371200 #m
[docs]@CheckInputsAreThreeComponentVectors('R_ECEF')
def ecef2eci(R_ECEF,jds):
"""Rotate a vector from cartesian Earth Centered Earth Fixed (ECEF) to
Cartesian Earth Centered Inertial (ECI)
PARAMETERS
----------
R_ECEF : np.ndarray
Array of n three component vectors ( shape=(n,3) ) in ECEF
jds : float or np.ndarray
Time stamp (as julian date) for all (if float) or each (if array)
of the vectors in R_ECEF
RETURNS
-------
R_ECI : np.ndarray
n three component vectors ( shape=(n,3) ) in ECI
"""
theta_GST = greenwich_mean_siderial_time(jds)
R_ECI = rot3(-1*theta_GST,R_ECEF)
return R_ECI
[docs]@CheckInputsAreThreeComponentVectors('R_ECI')
def eci2ecef(R_ECI,jds):
"""Rotate a vector from cartesian Earth Centered Inertial (ECI) to
cartesian Earth Centered Earth Fixed (ECEF)
PARAMETERS
----------
R_ECI : np.ndarray
Array of n three component vectors ( shape=(n,3) ) in ECI
jds : float or np.ndarray
Time stamp (as julian date) for all (if float) or each (if array)
of the vectors in R_ECEF
RETURNS
-------
R_ECEF : np.ndarray
n three component vectors ( shape=(n,3) ) in ECEF
"""
theta_GST = greenwich_mean_siderial_time(jds)
R_ECEF = rot3(theta_GST,R_ECI)
return R_ECEF
[docs]@CheckInputsAreThreeComponentVectors('R_ECEF')
def ecef_cart2spherical(R_ECEF):
"""Transform a vector in cartesian Earth Centered Earth Fixed (ECEF)
to geocentric spherical (a.k.a geographic coordinates)
PARAMETERS
----------
R_ECEF : np.ndarray
Array of n three component vectors ( shape=(n,3) ) in cartesian
ECEF
RETURNS
-------
lats : np.ndarray
Array of n latitude values (shape=(n,))
lons : np.ndarray
Array of n longitude values (shape=(n,)). Sign convention
is ISO 6709 (west is negative)
rs : np.ndarray
Array of n radii (distance from center of the earth)
(shape=(n,))
(same units as R_ECEF)
"""
xs = R_ECEF[:,0].flatten()
ys = R_ECEF[:,1].flatten()
zs = R_ECEF[:,2].flatten()
rs = np.sqrt(xs**2.+ys**2.+zs**2.)
lons = np.degrees(np.arctan2(ys,xs)) #Longitude is angle in x,y plane
lats = np.degrees(np.arcsin(zs/rs)) #Latitude is angle z-ward from x,y plane
return lats,lons,rs
[docs]@BroadcastLenOneInputsToMatchArrayInputs
def ecef_spherical2cart(lats,lons,rs):
"""Transform n positions in geocentric spherical, a.k.a. spherical Earth
Centered Earth Fixed (ECEF), a.k.a geographic to cartesian Earth Centered Earth
Fixed (ECEF)
PARAMETERS
----------
lats : float or np.ndarray
Array of n latitude values (shape=(n,))
lons : float or np.ndarray
Array of n longitude values (shape=(n,)). Sign convention
is ISO 6709 (west is negative)
rs : float or np.ndarray
Array of n radii (distance from center of the earth)
(shape=(n,))
RETURNS
-------
R_ECEF : np.ndarray
Array of n three component vectors ( shape=(n,3) ) in cartesian
ECEF
.. note::
Within the code the ISO 31-11 convention for theta (polar, zero
at positive z axis), and phi (azimuthal, zero at positive x axis)
is used
"""
thetas = np.radians(90.-lats)
phis = np.radians(lons)
x = rs*np.sin(thetas)*np.cos(phis)
y = rs*np.sin(thetas)*np.sin(phis)
z = rs*np.cos(thetas)
R_ECEF = np.concatenate([x.reshape(-1,1),
y.reshape(-1,1),
z.reshape(-1,1)],axis=1)
return R_ECEF
[docs]@CheckInputsAreThreeComponentVectors('R_ECEF')
def ecef2enu(R_ECEF,lats,lons):
"""Rotate n vectors from Earth Centered Earth Fixed (ECEF)
to local east, north, up coordinates centered at one location if only a
single lat/lon pair is passed, or n locations if lats and lons are
arrays of length n
PARAMETERS
----------
R_ECEF : np.ndarray
Array of n 3-component vectors (shape=(n,3)) in cartesian ECEF
lats : float or np.ndarray
Latitude(s) of ENU coordinates
lons : float or np.ndarray
Longitude(s) of ENU coordinates
RETURNS
-------
R_ENU : np.ndarray
Array of n 3-component vecotrs (shape=(n,3)) in cartesian ENU
(R_ENU[:,0] is eastward component, R_ENU[:,1] is northward, etc.)
"""
#This works even if lon is < -360, as numpy modulus returns
#the same sign as the denominator (360.)
lonrot = np.mod(90.+lons,360.)
colat = 90.-lats
R_ENU = rot1(np.radians(colat),rot3(np.radians(lonrot),R_ECEF))
return R_ENU
[docs]@CheckInputsAreThreeComponentVectors('R_ENU')
def enu2ecef(R_ENU,lats,lons):
"""Rotate n vectors from East North Up (ENU) (relative to location(s)
specified by lats and lons) to Earth Centered Earth Fixed (ECEF) coordinates
PARAMETERS
----------
R_ENU : np.ndarray
Array of n 3-component vectors (shape=(n,3)) in cartesian
ENU
lats : float or np.ndarray
Latitude(s) which define ENU directions
lons : float or np.ndarray
Longitude(s) which define ENU direction
RETURNS
-------
R_ECEF : np.ndarray
Array of n 3-component vectors (shape=(n,3)) in cartesian ECEF
"""
#This works even if lon is < -360, as numpy modulus returns
#the same sign as the denominator (360.)
lonrot = np.mod(90.+lons,360.)
colat = 90.-lats
R_ECEF = rot3(np.radians(-1*lonrot), rot1(np.radians(-1*colat),R_ENU) )
return R_ECEF