update EHS BDS identification, add isBDS50or60() function
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Junzi Sun
+67
-73
@@ -18,8 +18,9 @@ A python package for decoding ModeS (DF20, DF21) messages.
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"""
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from __future__ import absolute_import, print_function, division
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from . import util, modes_common
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from scipy.stats import multivariate_normal
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import numpy as np
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from pyModeS.decoder import util, modes_common
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from pyModeS.extra import aero
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def icao(msg):
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return modes_common.icao(msg)
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@@ -972,6 +973,61 @@ def vr60ins(msg):
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return roc
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def isBDS50or60(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.deg2rad(angle))
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vy = v * np.cos(np.deg2rad(angle))
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return vx, vy
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if not (isBDS50(msg) and isBDS60(msg)):
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return None
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h50 = trk50(msg)
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v50 = gs50(msg)
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h50 = np.nan if h50 is None else h50
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v50 = np.nan if v50 is None else v50
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h60 = hdg60(msg)
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m60 = mach60(msg)
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i60 = ias60(msg)
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h60 = np.nan if h60 is None else h60
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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*aero.kts))
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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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dist = np.linalg.norm(X-Mu, axis=1)
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BDS = allbds[np.nanargmin(dist)]
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return BDS
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def BDS(msg):
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"""Estimate the most likely BDS code of an message
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@@ -994,78 +1050,16 @@ def BDS(msg):
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is53 = isBDS53(msg)
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is60 = isBDS60(msg)
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BDS = ["BDS17", "BDS20", "BDS40", "BDS44", "BDS44REV", "BDS50", "BDS53", "BDS60"]
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allbds = np.array([
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"BDS17", "BDS20", "BDS40", "BDS44", "BDS44REV",
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"BDS50", "BDS53", "BDS60"
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])
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isBDS = [is17, is20, is40, is44, is44rev, is50, is53, is60]
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if sum(isBDS) == 0:
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bds = ','.join(sorted(allbds[isBDS]))
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if len(bds) == 0:
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return None
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elif sum(isBDS) == 1:
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return BDS[isBDS.index(True)]
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else:
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bds_ = [bds for (bds, i) in zip(BDS, isBDS) if i]
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return ','.join(bds_)
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def Vxy(V, angle):
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Vx = V*np.sin(np.deg2rad(angle))
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Vy = V*np.cos(np.deg2rad(angle))
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return Vx, Vy
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def BDSv2(msg, SPDref=np.nan, TRKref=np.nan, ALTref=np.nan):
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"""Use probabilistic method to determine 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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SPDref (float): reference speed (for example ADS-B GS)
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TRKref (float): reference track (for example ADS-B TRK)
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ALTref (float): reference altitude (for example ADS-B altitude)
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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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BDS = pms.ehs.BDS(msg)
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if type(BDS) != list:
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return BDS
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else:
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if 'BDS53' in BDS:
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BDS.remove('BDS53')
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if 'BDS40' in BDS:
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fms = pms.ehs.alt40fms(msg)
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mcp = pms.ehs.alt40mcp(msg)
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baro = pms.ehs.p40baro(msg)
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if fms != None:
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if (((fms % 100) <= 8) or ((fms % 100) >= 92)) and fms < 50500:
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return 'BDS40'
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if mcp != None:
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if (((mcp % 100) <= 8) or ((mcp % 100) >= 92)) and mcp < 50500:
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return 'BDS40'
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if baro != None:
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if (983 <= baro <= 1043): #1013 -+ 30
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return 'BDS40'
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if set(BDS).issubset(['BDS50', 'BDS60']):
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if ~(np.isnan(SPDref) or np.isnan(TRKref) or np.isnan(ALTref)):
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meanV = Vxy(SPDref, TRKref)
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sigmaV = 20
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covV = [[sigmaV**2, 0], [0, sigmaV**2]]
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try: # Because register field is not available.
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pBDS50 = multivariate_normal(meanV, covV).pdf(Vxy(pms.ehs.gs50(msg), pms.ehs.trk50(msg)))
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pBDS60_1 = multivariate_normal(meanV, covV).pdf(Vxy(aero.mach2tas(pms.ehs.mach60(msg), ALTref*aero.ft)/aero.kts, pms.ehs.hdg60(msg)))
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pBDS60_2 = multivariate_normal(meanV, covV).pdf(Vxy(aero.cas2tas(pms.ehs.ias60(msg)*aero.kts, ALTref*aero.ft)/aero.kts, pms.ehs.hdg60(msg)))
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pBDS60 = max(pBDS60_1, pBDS60_2)
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except:
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return BDS
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if pBDS50 + pBDS60 > 0: #Avoid None values
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if pBDS50 > pBDS60:
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return 'BDS50'
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elif pBDS50 < pBDS60:
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return 'BDS60'
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return BDS
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return bds
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