124 lines
3.5 KiB
Python
124 lines
3.5 KiB
Python
# Copyright (C) 2015 Junzi Sun (TU Delft)
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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"""
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Common functions for Mode-S decoding
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"""
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from __future__ import absolute_import, print_function, division
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import numpy as np
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from pyModeS.extra import aero
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from pyModeS.decoder.common import allzeros
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from pyModeS.decoder.bds import bds05, bds06, bds08, bds09, \
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bds10, bds17, bds20, bds30, bds40, bds44, bds50, bds53, bds60
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def is50or60(msg, spd_ref, trk_ref, alt_ref):
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"""Use reference ground speed and trk to determine BDS50 and DBS60
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Args:
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msg (String): 28 bytes hexadecimal message string
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spd_ref (float): reference speed (ADS-B ground speed), kts
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trk_ref (float): reference track (ADS-B track angle), deg
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alt_ref (float): reference altitude (ADS-B altitude), ft
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Returns:
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String or None: BDS version, or possible versions, or None if nothing matches.
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"""
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def vxy(v, angle):
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vx = v * np.sin(np.radians(angle))
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vy = v * np.cos(np.radians(angle))
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return vx, vy
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if not (bds50.is50(msg) and bds60.is60(msg)):
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return None
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h50 = bds50.trk50(msg)
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v50 = bds50.gs50(msg)
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if h50 is None or v50 is None:
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return 'BDS50,BDS60'
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h60 = bds60.hdg60(msg)
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m60 = bds60.mach60(msg)
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i60 = bds60.ias60(msg)
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if h60 is None or (m60 is None and i60 is None):
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return 'BDS50,BDS60'
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m60 = np.nan if m60 is None else m60
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i60 = np.nan if i60 is None else i60
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XY5 = vxy(v50*aero.kts, h50)
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XY6m = vxy(aero.mach2tas(m60, alt_ref*aero.ft), h60)
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XY6i = vxy(aero.cas2tas(i60*aero.kts, alt_ref*aero.ft), h60)
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allbds = ['BDS50', 'BDS60', 'BDS60']
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X = np.array([XY5, XY6m, XY6i])
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Mu = np.array(vxy(spd_ref*aero.kts, trk_ref))
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# compute Mahalanobis distance matrix
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# Cov = [[20**2, 0], [0, 20**2]]
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# mmatrix = np.sqrt(np.dot(np.dot(X-Mu, np.linalg.inv(Cov)), (X-Mu).T))
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# dist = np.diag(mmatrix)
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# since the covariance matrix is identity matrix,
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# M-dist is same as eculidian distance
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try:
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dist = np.linalg.norm(X-Mu, axis=1)
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BDS = allbds[np.nanargmin(dist)]
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except ValueError:
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return 'BDS50,BDS60'
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return BDS
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def infer(msg):
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"""Estimate the most likely BDS code of an message
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Args:
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msg (String): 28 bytes hexadecimal message string
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Returns:
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String or None: BDS version, or possible versions, or None if nothing matches.
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"""
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if allzeros(msg):
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return None
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IS10 = bds10.is10(msg)
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IS17 = bds17.is17(msg)
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IS20 = bds20.is20(msg)
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IS30 = bds30.is30(msg)
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IS40 = bds40.is40(msg)
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IS50 = bds50.is50(msg)
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IS60 = bds60.is60(msg)
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allbds = np.array([
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"BDS10", "BDS17", "BDS20", "BDS30", "BDS40", "BDS50", "BDS60"
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])
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mask = [IS10, IS17, IS20, IS30, IS40, IS50, IS60]
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bds = ','.join(sorted(allbds[mask]))
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if len(bds) == 0:
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return None
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else:
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return bds
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