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Added a true radio horizon calculator to geodesy functions

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Mark Qvist 2023-10-25 18:50:27 +02:00
parent e6be975e6e
commit 07202396ae
1 changed files with 54 additions and 22 deletions
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76
sbapp/sideband/geo.py
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@ -1,5 +1,6 @@
import time
from math import pi, sin, cos, acos, tan, atan, atan2
import RNS
from math import pi, sin, cos, acos, asin, tan, atan, atan2
from math import radians, degrees, sqrt
# WGS84 Parameters
@ -17,18 +18,6 @@ eccentricity_squared = 2*ellipsoid_flattening-pow(ellipsoid_flattening,2)
mean_earth_radius = (1/3)*(2*equatorial_radius+polar_radius)
def central_angle(c1, c2):
lat1 = radians(c1[0]); lon1 = radians(c1[1])
lat2 = radians(c2[0]); lon2 = radians(c2[1])
d_lat = abs(lat1-lat2)
d_lon = abs(lon1-lon2)
ca = acos(
sin(lat1) * sin(lat2) +
cos(lat1) * cos(lat2) * cos(d_lon)
)
return ca
def geocentric_latitude(geodetic_latitude):
e2 = eccentricity_squared
lat = radians(geodetic_latitude)
@ -95,6 +84,21 @@ def euclidian_distance(c1, c2, ellipsoid=True):
else:
return None
def central_angle(c1, c2):
lat1 = radians(c1[0]); lon1 = radians(c1[1])
lat2 = radians(c2[0]); lon2 = radians(c2[1])
d_lat = abs(lat1-lat2)
d_lon = abs(lon1-lon2)
ca = acos(
sin(lat1) * sin(lat2) +
cos(lat1) * cos(lat2) * cos(d_lon)
)
return ca
def arc_length(central_angle, r=mean_earth_radius):
return r*central_angle;
def spherical_distance(c1, c2, altitude=0, r=mean_earth_radius):
d = (r+altitude)*central_angle(c1, c2)
return d
@ -243,20 +247,48 @@ def angle_to_horizon(c, ellipsoid=False):
else:
r = mean_earth_radius
h = c[2]
if h < 0: h = 0
return degrees(-acos(r/(r+h)))
def radio_horizon(c1, c2, ellipsoid=False):
# dr = 4.12*(√h1 + √h2)
def euclidian_horizon_distance(h):
r = mean_earth_radius
b = r
c = r+h
a = c**2 - b**2
return sqrt(a)
def euclidian_horizon_arc(h):
r = mean_earth_radius
d = euclidian_horizon_distance(h)
a = d; b = r; c = r+h
arc = acos( (b**2+c**2-a**2) / (2*b*c) )
return arc
def radio_horizon(h, rh=0, ellipsoid=False):
if ellipsoid:
raise NotImplementedError("Radio horizon on the ellipsoid is not yet implemented")
else:
h1 = c1[2]
h2 = c2[2]
ed = euclidian_distance(c1,c2)
rh1 = 1e3*4.12*(sqrt(h1))
rh2 = 1e3*4.12*(sqrt(h2))
rhc = 1e3*4.12*(sqrt(h1) + sqrt(h2))
return (rh1, rh2, rhc, rhc > ed)
geocentric_angle_to_horizon = euclidian_horizon_arc(h)
geodesic_distance = arc_length(geocentric_angle_to_horizon, r=mean_earth_radius)
return geodesic_distance
def shared_radio_horizon(c1, c2,):
lat1 = c1[0]; lon1 = c1[1]; h1 = c1[2]
lat2 = c2[0]; lon2 = c2[1]; h2 = c2[2]
geodesic_distance = orthodromic_distance((lat1, lon1, 0.0), (lat2, lon2, 0.0) , ellipsoid=False)
antenna_distance = euclidian_distance(c1,c2,ellipsoid=False)
rh1 = radio_horizon(h1)
rh2 = radio_horizon(h2)
rhc = rh1+rh2
return {
"horizon1":rh1, "horizon2":rh2, "shared":rhc,
"within":rhc > geodesic_distance,
"geodesic_distance": geodesic_distance,
"antenna_distance": antenna_distance
}
def tests():
import RNS