Source code for pymap3d.haversine

#!/usr/bin/env python
# Copyright (c) 2014-2018 Michael Hirsch, Ph.D.
#
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from numpy import cos, arcsin, sqrt, radians, degrees
from astropy.coordinates.angle_utilities import angular_separation
"""
Michael Hirsch

Note: adding decimal points to the constants made 0 difference in %timeit execution time

The Meeus algorithm is about 9.5% faster than Astropy/Vicenty on my PC,
and gives virtually identical result
within double precision arithmetic limitations
"""


[docs]def angledist_meeus(r0, d0, r1, d1): """ inputs: r0,d0 for first point, rightAscension,Declination [degrees] or (azimuth,elevation) r1,d1 for second point, rightAscension,Declination [degrees] or (azimuth,elevation) (or, azimuth/elevation respectively) from "Astronomical Algorithms" by Jean Meeus Ch. 16 p. 111 (16.5) gives angular distance in degrees between two rightAscension,Declination points in the sky. Neglecting atmospheric effects, of course. Advantage of Meeus haversine method is stability all the way to exactly 0 deg. assumes degrees input, degrees output either the arrays must be the same size, or one of them must be a scalar """ r0 = radians(r0) r1 = radians(r1) d0 = radians(d0) d1 = radians(d1) dist_rad = 2 * arcsin( sqrt( haversine(d1 - d0) + cos(d0) * cos(d1) * haversine(r1 - r0))) return degrees(dist_rad)
[docs]def angledist(lon1, lat1, lon2, lat2): """ inputs: r0,d0 for first point, rightAscension,Declination [degrees] or (azimuth,elevation) r1,d1 for second point, rightAscension,Declination [degrees] or (azimuth,elevation) (or, azimuth/elevation respectively) For reference, this is from astropy astropy/coordinates/angle_utilities.py Angular separation between two points on a sphere. """ return degrees(angular_separation(radians(lon1), radians(lat1), radians(lon2), radians(lat2)))
[docs]def haversine(theta): """ Compute haversine of angle theta (radians) http://en.wikipedia.org/wiki/Haversine Meeus p. 111 """ return (1 - cos(theta)) / 2.