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Author SHA1 Message Date
Junzi Sun
59d21de725 Merge branch 'master' into adsb_encoder 2020-05-04 01:53:27 +02:00
Junzi Sun
aff0f75de2 BDS08 and BDS09 encoders 2020-05-03 23:29:10 +02:00
7 changed files with 260 additions and 0 deletions

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from .bds.bds08 import me08
from .bds.bds09 import me09
from pyModeS import common
def encode_adsb(**kwargs):
"""Encode ADS-B message.
Args:
icao (string): Transponder ICAO address (6 hexdigits)
capability (int): Transponder capability, between 0 and 7
typecode (int): Typecode, less than 32
callsign (string): Callsign (6 hexdigits)
category (int): Aircraft category, between 0 and 7, Default to 0.
speed (int): Speed in knots.
angle (float): Track angle or heading angle in degrees.
vertical_rate (int): vertical rate in feet/minute
intent_change (int): Intent change flag, 0 or 1. Default to 0.
ifr_capability (int): IFR capability flag, 0 or 1. Default to 1.
navigation_quality (int): NUC (ver 0) or NACv (ver 1, 2), between 0 and 7.
Default to 0.
supersonic (bool): Is this a supersonic flight? Default to False.
speed_type (str): Speed type: GS, IAS, or TAS. Default to GS.
vertical_rate_source (str): GNSS or BARO. Default to BARO.
gnss_baro_alt_diff (int): Different between GNSS and barometric altitude in feet.
Negative value indicates GNSS altitude below barometric altitude. Default to 0
Returns:
string: 28 hexdigits raw message
"""
tc = kwargs.get("typecode")
if 1 <= tc <= 4:
me = me08(**kwargs)
elif tc == 19:
me = me09(**kwargs)
msg = _constuct(**dict(kwargs, me=me))
return msg
def _constuct(**kwargs):
icao = kwargs.get("icao")
me = kwargs.get("me")
capability = kwargs.get("capability", 6)
if icao is None or len(icao) != 6:
raise Exception("Transponder address must be 6 hexadecimal characters.")
if me is None or len(me) != 14:
raise Exception("Message be 14 hexadecimal characters.")
if capability > 6:
raise Exception("Transponder capability must be smaller than 7.")
header_bin = "10001" + "{0:03b}".format(capability)
header_hex = "{0:02X}".format(int(header_bin, 2))
msg = header_hex + icao + me + "000000"
pi = common.crc(msg, encode=True)
pi_hex = "{0:06X}".format(pi)
msg = msg[:-6] + pi_hex
return msg

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# ------------------------------------------
# BDS 0,5
# ADS-B TC=9-18
# Airborn position
# ------------------------------------------

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# ------------------------------------------
# BDS 0,6
# ADS-B TC=5-8
# Surface position
# ------------------------------------------

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# ------------------------------------------
# BDS 0,8
# ADS-B TC=1-4
# Aircraft identitification and category
# ------------------------------------------
from pyModeS import common
charmap = "#ABCDEFGHIJKLMNOPQRSTUVWXYZ##### ###############0123456789######"
def me08(callsign, **kwargs):
cs = callsign
tc = kwargs.get("typecode")
cat = kwargs.get("category", 0)
if len(cs) > 8:
raise Exception("callsign must contain less than 9 characters")
if tc > 4:
raise Exception("typecode must be less 5")
if cat > 7:
raise Exception("category must be less 8")
if not cs.isalnum():
raise Exception("callsign must only contain alphanumeric characters")
cs = "{:<8}".format(cs.upper())
idx = [charmap.index(c) for c in cs]
me_bin = (
"{0:05b}".format(tc)
+ "{0:03b}".format(cat)
+ "".join("{0:06b}".format(i) for i in idx)
)
me_hex = "{0:04X}".format(int(me_bin, 2))
return me_hex

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# ------------------------------------------
# BDS 0,9
# ADS-B TC=19
# Aircraft Airborn velocity
# ------------------------------------------
import numpy as np
def me09(speed, angle, vertical_rate, **kwargs):
spd = speed
agl = angle
vr = vertical_rate
tc = kwargs.get("typecode")
intent = kwargs.get("intent_change", 0)
ifr = kwargs.get("ifr_capability", 1)
navq = kwargs.get("navigation_quality", 0)
supersonic = kwargs.get("supersonic", False)
spd_type = kwargs.get("speed_type", "gs").lower()
vr_source = kwargs.get("vertical_rate_source", "baro").lower()
alt_diff = kwargs.get("gnss_baro_alt_diff", 0)
if tc != 19:
raise Exception("Typecode must be 19.")
if intent not in (0, 1):
raise Exception("Intent change flag must be 0 or 1.")
if ifr not in (0, 1):
raise Exception("IFR capability flag must be 0 or 1.")
if type(supersonic) != bool:
raise Exception("Subsonic flag must be True or False.")
if navq > 7:
raise Exception("Navigation quality indicator must be smaller than 8.")
if spd_type not in ["gs", "tas"]:
raise Exception("Speed type must be 'gs', 'ias', or 'tas'.")
if vr_source not in ["baro", "gnss"]:
raise Exception("Vertical rate source must be 'baro' or 'gnss'.")
me_bin = ""
# typecode
me_bin += "{0:05b}".format(tc)
# sub-type
if supersonic:
if spd_type == "gs":
me_bin += "010"
else:
me_bin += "100"
else:
if spd_type == "gs":
me_bin += "001"
else:
me_bin += "011"
# intent, ifr, navigation quality
me_bin += str(intent) + str(ifr) + "{0:03b}".format(navq)
# speed and angle part
if spd_type == "gs":
vx = spd * np.sin(np.radians(agl))
vy = spd * np.cos(np.radians(agl))
if supersonic:
vx /= 4
vy /= 4
vx = int(round(vx))
vy = int(round(vy))
sew = "0" if vx >= 0 else "1"
sns = "0" if vy >= 0 else "1"
vew = "{0:010b}".format(min(abs(vx), 1023) + 1)
vns = "{0:010b}".format(min(abs(vy), 1023) + 1)
me_bin += sew + vew + sns + vns
elif spd_type == "ias" or spd_type == "tas":
hdg = int(round(agl * 1024 / 360))
hdg = min(hdg, 1023)
air_type = "1" if spd_type == "tas" else "0"
if supersonic:
spd /= 4
spd = min(int(round(spd)), 1023)
me_bin += "1" + "{0:010b}".format(hdg) + air_type + "{0:010b}".format(spd)
# vertical rate source
me_bin += "1" if vr_source == "baro" else "0"
# vertical rate
me_bin += "0" if vr > 0 else "1"
vr = int(round((abs(vr) / 64 + 1)))
vr = min(vr, 511)
me_bin += "{0:09b}".format(vr)
# reserved
me_bin += "00"
# altitude difference
me_bin += "1" if alt_diff < 0 else "0"
alt_diff = int(round(abs(alt_diff) / 25 + 1))
alt_diff = min(alt_diff, 127)
me_bin += "{0:07b}".format(alt_diff)
print(me_bin)
# convert to hexdigits
me_hex = "{0:04X}".format(int(me_bin, 2))
return me_hex

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tests/test_encoder.py Normal file
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from pyModeS import encoder
def test_identification():
msg = encoder.encode_adsb(
icao="406B90", typecode=4, capability=5, category=0, callsign="EZY85MH"
)
assert msg == "8D406B902015A678D4D220AA4BDA"
def test_speed():
msg = encoder.encode_adsb(
icao="485020",
typecode=19,
capability=5,
speed_type="gs",
speed=159,
angle=182.88,
vertical_rate=-832,
vertical_rate_source="gnss",
gnss_baro_alt_diff=550,
)
assert msg == "8D485020994409940838175B284F"