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@sbarratt
Last active Sep 21, 2021
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This script provides coordinate transformations between geodetic, ecef and enu in python. Based on https://gist.github.com/govert/1b373696c9a27ff4c72a.
"""
This script provides coordinate transformations from Geodetic -> ECEF, ECEF -> ENU
and Geodetic -> ENU (the composition of the two previous functions). Running the script
by itself runs tests.
based on https://gist.github.com/govert/1b373696c9a27ff4c72a.
"""
import math
a = 6378137
b = 6356752.3142
f = (a - b) / a
e_sq = f * (2-f)
def geodetic_to_ecef(lat, lon, h):
# (lat, lon) in WSG-84 degrees
# h in meters
lamb = math.radians(lat)
phi = math.radians(lon)
s = math.sin(lamb)
N = a / math.sqrt(1 - e_sq * s * s)
sin_lambda = math.sin(lamb)
cos_lambda = math.cos(lamb)
sin_phi = math.sin(phi)
cos_phi = math.cos(phi)
x = (h + N) * cos_lambda * cos_phi
y = (h + N) * cos_lambda * sin_phi
z = (h + (1 - e_sq) * N) * sin_lambda
return x, y, z
def ecef_to_enu(x, y, z, lat0, lon0, h0):
lamb = math.radians(lat0)
phi = math.radians(lon0)
s = math.sin(lamb)
N = a / math.sqrt(1 - e_sq * s * s)
sin_lambda = math.sin(lamb)
cos_lambda = math.cos(lamb)
sin_phi = math.sin(phi)
cos_phi = math.cos(phi)
x0 = (h0 + N) * cos_lambda * cos_phi
y0 = (h0 + N) * cos_lambda * sin_phi
z0 = (h0 + (1 - e_sq) * N) * sin_lambda
xd = x - x0
yd = y - y0
zd = z - z0
xEast = -sin_phi * xd + cos_phi * yd
yNorth = -cos_phi * sin_lambda * xd - sin_lambda * sin_phi * yd + cos_lambda * zd
zUp = cos_lambda * cos_phi * xd + cos_lambda * sin_phi * yd + sin_lambda * zd
return xEast, yNorth, zUp
def geodetic_to_enu(lat, lon, h, lat_ref, lon_ref, h_ref):
x, y, z = geodetic_to_ecef(lat, lon, h)
return ecef_to_enu(x, y, z, lat_ref, lon_ref, h_ref)
if __name__ == '__main__':
def are_close(a, b):
return abs(a-b) < 1e-4
latLA = 34.00000048
lonLA = -117.3335693
hLA = 251.702
x0, y0, z0 = geodetic_to_ecef(latLA, lonLA, hLA)
x = x0 + 1
y = y0
z = z0
xEast, yNorth, zUp = ecef_to_enu(x, y, z, latLA, lonLA, hLA)
assert are_close(0.88834836, xEast)
assert are_close(0.25676467, yNorth)
assert are_close(-0.38066927, zUp)
x = x0
y = y0 + 1
z = z0
xEast, yNorth, zUp = ecef_to_enu(x, y, z, latLA, lonLA, hLA)
assert are_close(-0.45917011, xEast)
assert are_close(0.49675810, yNorth)
assert are_close(-0.73647416, zUp)
x = x0
y = y0
z = z0 + 1
xEast, yNorth, zUp = ecef_to_enu(x, y, z, latLA, lonLA, hLA)
assert are_close(0.00000000, xEast)
assert are_close(0.82903757, yNorth)
assert are_close(0.55919291, zUp)
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