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vebit-map/position.py

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#!/usr/bin/env python3
import math
def arc_to_deg(arc):
"""convert spherical arc length [m] to great circle distance [deg]"""
return float(arc)/6371/1000 * 180/math.pi
def deg_to_arc(deg):
"""convert great circle distance [deg] to spherical arc length [m]"""
return float(deg)*6371*1000 * math.pi/180
def latlon_to_xyz(lat,lon):
"""Convert angluar to cartesian coordiantes
latitude is the 90deg - zenith angle in range [-90;90]
lonitude is the azimuthal angle in range [-180;180]
"""
r = 6371 # https://en.wikipedia.org/wiki/Earth_radius
theta = math.pi/2 - math.radians(lat)
phi = math.radians(lon)
x = r * math.sin(theta) * math.cos(phi) # bronstein (3.381a)
y = r * math.sin(theta) * math.sin(phi)
z = r * math.cos(theta)
return [x,y,z]
def xyz_to_latlon (x,y,z):
"""Convert cartesian to angular lat/lon coordiantes"""
r = math.sqrt(x**2 + y**2 + z**2)
theta = math.asin(z/r) # https://stackoverflow.com/a/1185413/4933053
phi = math.atan2(y,x)
lat = math.degrees(theta)
lon = math.degrees(phi)
return [lat,lon]