Source code for pyModeS.decoder.bds

# Copyright (C) 2015 Junzi Sun (TU Delft)

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# GNU General Public License for more details.

# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <>.

Common functions for Mode-S decoding

import numpy as np

from pyModeS.extra import aero
from pyModeS import common

from pyModeS.decoder.bds import (

[docs]def is50or60(msg, spd_ref, trk_ref, alt_ref): """Use reference ground speed and trk to determine BDS50 and DBS60. Args: msg (str): 28 hexdigits string spd_ref (float): reference speed (ADS-B ground speed), kts trk_ref (float): reference track (ADS-B track angle), deg alt_ref (float): reference altitude (ADS-B altitude), ft Returns: String or None: BDS version, or possible versions, or None if nothing matches. """ def vxy(v, angle): vx = v * np.sin(np.radians(angle)) vy = v * np.cos(np.radians(angle)) return vx, vy if not (bds50.is50(msg) and bds60.is60(msg)): return None h50 = bds50.trk50(msg) v50 = bds50.gs50(msg) if h50 is None or v50 is None: return "BDS50,BDS60" h60 = bds60.hdg60(msg) m60 = bds60.mach60(msg) i60 = bds60.ias60(msg) if h60 is None or (m60 is None and i60 is None): return "BDS50,BDS60" m60 = np.nan if m60 is None else m60 i60 = np.nan if i60 is None else i60 XY5 = vxy(v50 * aero.kts, h50) XY6m = vxy(aero.mach2tas(m60, alt_ref * aero.ft), h60) XY6i = vxy(aero.cas2tas(i60 * aero.kts, alt_ref * aero.ft), h60) allbds = ["BDS50", "BDS60", "BDS60"] X = np.array([XY5, XY6m, XY6i]) Mu = np.array(vxy(spd_ref * aero.kts, trk_ref)) # compute Mahalanobis distance matrix # Cov = [[20**2, 0], [0, 20**2]] # mmatrix = np.sqrt(, np.linalg.inv(Cov)), (X-Mu).T)) # dist = np.diag(mmatrix) # since the covariance matrix is identity matrix, # M-dist is same as eculidian distance try: dist = np.linalg.norm(X - Mu, axis=1) BDS = allbds[np.nanargmin(dist)] except ValueError: return "BDS50,BDS60" return BDS
[docs]def infer(msg, mrar=False): """Estimate the most likely BDS code of an message. Args: msg (str): 28 hexdigits string mrar (bool): Also infer MRAR (BDS 44) and MHR (BDS 45). Defaults to False. Returns: String or None: BDS version, or possible versions, or None if nothing matches. """ df = common.df(msg) if common.allzeros(msg): return "EMPTY" # For ADS-B / Mode-S extended squitter if df == 17: tc = common.typecode(msg) if 1 <= tc <= 4: return "BDS08" # identification and category if 5 <= tc <= 8: return "BDS06" # surface movement if 9 <= tc <= 18: return "BDS05" # airborne position, baro-alt if tc == 19: return "BDS09" # airborne velocity if 20 <= tc <= 22: return "BDS05" # airborne position, gnss-alt if tc == 28: return "BDS61" # aircraft status if tc == 29: return "BDS62" # target state and status if tc == 31: return "BDS65" # operational status # For Comm-B replies IS10 = bds10.is10(msg) IS17 = bds17.is17(msg) IS20 = bds20.is20(msg) IS30 = bds30.is30(msg) IS40 = bds40.is40(msg) IS50 = bds50.is50(msg) IS60 = bds60.is60(msg) IS44 = bds44.is44(msg) IS45 = bds45.is45(msg) if mrar: allbds = np.array( [ "BDS10", "BDS17", "BDS20", "BDS30", "BDS40", "BDS44", "BDS45", "BDS50", "BDS60", ] ) mask = [IS10, IS17, IS20, IS30, IS40, IS44, IS45, IS50, IS60] else: allbds = np.array( ["BDS10", "BDS17", "BDS20", "BDS30", "BDS40", "BDS50", "BDS60"] ) mask = [IS10, IS17, IS20, IS30, IS40, IS50, IS60] bds = ",".join(sorted(allbds[mask])) if len(bds) == 0: return None else: return bds