# Copyright (c) 2021 CNES/JPL
#
# All rights reserved. Use of this source code is governed by a
# BSD-style license that can be found in the LICENSE file.
"""
Timing errors
-------------
"""
from typing import Dict
import numpy as np
from .. import random_signal
from .. import CELERITY
from .. import settings
[docs]class Timing:
"""
Timing errors
Args:
parameters (settings.Parameters): Simulation settings
timing_psd (numpy.ndarray): Power spectral density the timing error
spatial_frequency (numpy.ndarray): Spatial frequency
"""
CONVERSION_FACTOR = CELERITY * 5e-13
[docs] def __init__(self, parameters: settings.Parameters, timing_psd: np.ndarray,
spatial_frequency: np.ndarray) -> None:
# Store the generation parameters of the random signal.
self.rng_l = parameters.rng()
self.rng_r = parameters.rng()
self.len_repeat = parameters.len_repeat
self.delta_al = parameters.delta_al
# Get baseline dilation power spectrum
self.timing_psd = timing_psd
self.spatial_frequency = spatial_frequency
[docs] def _generate_1d(self, x_al: np.ndarray) -> np.ndarray:
# Generate 1d timing using the power spectrum:
timing_l = random_signal.gen_signal_1d(self.spatial_frequency,
self.timing_psd,
x_al,
rng=self.rng_l,
fmin=1 / self.len_repeat,
fmax=1 / (2 * self.delta_al),
alpha=10)
timing_r = random_signal.gen_signal_1d(self.spatial_frequency,
self.timing_psd,
x_al,
rng=self.rng_r,
fmin=1 / self.len_repeat,
fmax=1 / (2 * self.delta_al),
alpha=10)
# Compute the corresponding timing error on the swath in m
return np.array([
self.CONVERSION_FACTOR * timing_l,
self.CONVERSION_FACTOR * timing_r
]).T
[docs] def generate(self, x_al: np.ndarray,
x_ac: np.ndarray) -> Dict[str, np.ndarray]:
"""Generate timing errors
Args:
x_al (numpy.ndarray): Along track distance
x_ac (numpy.ndarray): Across track distance
Returns:
dict: variable name and errors simulated.
"""
timing_1d = self._generate_1d(x_al)
num_pixels = x_ac.shape[0]
swath_center = num_pixels // 2
num_lines = timing_1d.shape[0]
timing = np.empty((num_lines, num_pixels))
ones_ac = np.ones((swath_center, ))
timing[:, :swath_center] = ones_ac * timing_1d[:, 0, np.newaxis]
timing[:, swath_center:] = ones_ac * timing_1d[:, 1, np.newaxis]
return {"simulated_error_timing": timing}