"""Copyright 2015 Roger R Labbe Jr.
FilterPy library.
http://github.com/rlabbe/filterpy
Documentation at:
https://filterpy.readthedocs.org
Supporting book at:
https://github.com/rlabbe/Kalman-and-Bayesian-Filters-in-Python
This is licensed under an MIT license. See the readme.MD file
for more information.
"""
from numpy.random import randn
from math import radians, atan2
class RadarSim(object):
""" Simulates the radar signal returns from an object flying
at a constant altityude and velocity in 1D. Assumes random
process noise - altitude and velocity varies a bit for each call.
"""
def __init__(self, dt, pos=0., vel=100., alt=1000.):
self.dt = dt
self.pos = pos
self.vel = vel
self.alt = alt
def get_range(self, process_err_pct=0.05):
""" Returns slant range to the object. Call once for each
new measurement at dt time from last call.
"""
vel = self.vel + 5*randn()
alt = self.alt + 10*randn()
self.pos += vel*self.dt
err = (self.pos * process_err_pct) * randn()
slant_range = (self.pos**2 + alt**2)**.5 + err
return slant_range
def get_range_bearing(self, angle_sigma_deg=1.):
r = self.get_range()
a = atan2(self.alt, self.x)
a += randn() * radians(angle_sigma_deg)
return r, a
