def callsign(msg):
"""Aircraft callsign
Args:
msg (string): 28 bytes hexadecimal message string
Returns:
string: callsign
"""
if typecode(msg) < 1 or typecode(msg) > 4:
raise RuntimeError("%s: Not a identification message" % msg)
chars = '#ABCDEFGHIJKLMNOPQRSTUVWXYZ#####_###############0123456789######'
msgbin = util.hex2bin(msg)
csbin = msgbin[40:96]
cs = ''
cs += chars[util.bin2int(csbin[0:6])]
cs += chars[util.bin2int(csbin[6:12])]
cs += chars[util.bin2int(csbin[12:18])]
cs += chars[util.bin2int(csbin[18:24])]
cs += chars[util.bin2int(csbin[24:30])]
cs += chars[util.bin2int(csbin[30:36])]
cs += chars[util.bin2int(csbin[36:42])]
cs += chars[util.bin2int(csbin[42:48])]
# clean string, remove spaces and marks, if any.
# cs = cs.replace('_', '')
cs = cs.replace('#', '')
return cs
def isBDS60(msg):
"""Check if a message is likely to be BDS code 6,0
Args:
msg (String): 28 bytes hexadecimal message string
Returns:
bool: True or False
"""
# status bit 1, 13, 24, 35, 46
d = util.hex2bin(data(msg))
result = True
result = result & checkbits(d, 1, 2, 12) & checkbits(d, 13, 14, 23) \
& checkbits(d, 24, 25, 34) & checkbits(d, 35, 36, 45) \
& checkbits(d, 46, 47, 56)
if not (1 < ias(msg) < 500):
result &= False
if not (0.0 < mach(msg) < 1.0):
result &= False
if abs(baro_vr(msg)) > 5000:
result &= False
if abs(ins_vr(msg)) > 5000:
result &= False
return result
def isBDS50(msg):
"""Check if a message is likely to be BDS code 5,0
Args:
msg (String): 28 bytes hexadecimal message string
Returns:
bool: True or False
"""
# status bit 1, 12, 24, 35, 46
d = util.hex2bin(data(msg))
result = True
result = result & checkbits(d, 1, 3, 11) & checkbits(d, 12, 13, 23) \
& checkbits(d, 24, 25, 34) & checkbits(d, 35, 36, 45) \
& checkbits(d, 46, 47, 56)
if d[2:11] == "000000000":
result &= True
else:
if abs(roll(msg)) > 30:
result &= False
if gs(msg) > 500:
result &= False
if tas(msg) > 500:
result &= False
if abs(tas(msg) - gs(msg)) > 100:
result &= False
return result
def test_crc():
# crc decoder
checksum = util.crc("8D406B902015A678D4D220AA4BDA")
assert checksum == "000000000000000000000000"
# crc encoder
parity = util.crc("8D406B902015A678D4D220AA4BDA", encode=True)
assert util.hex2bin("AA4BDA") == parity
def test_crc():
# crc decoder
checksum = util.crc("8D406B902015A678D4D220AA4BDA")
assert checksum == "000000000000000000000000"
# crc encoder
parity = util.crc("8D406B902015A678D4D220AA4BDA", encode=True)
assert util.hex2bin("AA4BDA") == parity
def typecode(msg):
"""Type code of ADS-B message
Args:
msg (string): 28 bytes hexadecimal message string
Returns:
int: type code number
"""
msgbin = util.hex2bin(msg)
return util.bin2int(msgbin[32:37])
def ias(msg):
"""Indicated airspeed
Args:
msg (String): 28 bytes hexadecimal message (BDS60) string
Returns:
int: indicated airspeed in knots
"""
d = util.hex2bin(data(msg))
ias = util.bin2int(d[13:23]) # kts
return ias
def tas(msg):
"""Aircraft true airspeed
Args:
msg (String): 28 bytes hexadecimal message (BDS50) string
Returns:
int: true airspeed in knots
"""
d = util.hex2bin(data(msg))
spd = util.bin2int(d[46:56]) * 2 # kts
return spd
def gs(msg):
"""Aircraft ground speed
Args:
msg (String): 28 bytes hexadecimal message (BDS50) string
Returns:
int: ground speed in knots
"""
d = util.hex2bin(data(msg))
spd = util.bin2int(d[24:34]) * 2 # kts
return spd
def pbaro(msg):
"""Barometric pressure setting
Args:
msg (String): 28 bytes hexadecimal message (BDS40) string
Returns:
float: pressure in millibar
"""
d = util.hex2bin(data(msg))
p = util.bin2int(d[27:39]) * 0.1 + 800 # millibar
return p
def mach(msg):
"""Aircraft MACH number
Args:
msg (String): 28 bytes hexadecimal message (BDS60) string
Returns:
float: MACH number
"""
d = util.hex2bin(data(msg))
mach = util.bin2int(d[24:34]) * 2.048 / 512.0
return round(mach, 3)
def alt_fms(msg):
"""Selected altitude, FMS
Args:
msg (String): 28 bytes hexadecimal message (BDS40) string
Returns:
int: altitude in feet
"""
d = util.hex2bin(data(msg))
alt = util.bin2int(d[14:26]) * 16 # ft
return alt
def track(msg):
"""True track angle
Args:
msg (String): 28 bytes hexadecimal message (BDS50) string
Returns:
float: angle in degrees to true north (from 0 to 360)
"""
d = util.hex2bin(data(msg))
sign = int(d[12]) # 1 -> west
value = util.bin2int(d[13:23]) * 90 / 512.0 # degree
angle = 360 - value if sign else value
return round(angle, 1)
def rtrack(msg):
"""Track angle rate
Args:
msg (String): 28 bytes hexadecimal message (BDS50) string
Returns:
float: angle rate in degrees/second
"""
d = util.hex2bin(data(msg))
sign = int(d[35]) # 1 -> minus
value = util.bin2int(d[36:45]) * 8 / 256.0 # degree / sec
angle = -1 * value if sign else value
return round(angle, 3)
def heading(msg):
"""Megnetic heading of aircraft
Args:
msg (String): 28 bytes hexadecimal message (BDS60) string
Returns:
float: heading in degrees to megnetic north (from 0 to 360)
"""
d = util.hex2bin(data(msg))
sign = int(d[1]) # 1 -> west
value = util.bin2int(d[2:12]) * 90 / 512.0 # degree
hdg = 360 - value if sign else value
return round(hdg, 1)
def oe_flag(msg):
"""Check the odd/even flag. Bit 54, 0 for even, 1 for odd.
Args:
msg (string): 28 bytes hexadecimal message string
Returns:
int: 0 or 1, for even or odd frame
"""
if typecode(msg) < 5 or typecode(msg) > 18:
raise RuntimeError("%s: Not a position message" % msg)
msgbin = util.hex2bin(msg)
return int(msgbin[53])
def cprlon(msg):
"""CPR encoded longitude
Args:
msg (string): 28 bytes hexadecimal message string
Returns:
int: encoded longitude
"""
if typecode(msg) < 5 or typecode(msg) > 18:
raise RuntimeError("%s: Not a position message" % msg)
msgbin = util.hex2bin(msg)
return util.bin2int(msgbin[71:88])
def baro_vr(msg):
"""Vertical rate from barometric measurement
Args:
msg (String): 28 bytes hexadecimal message (BDS60) string
Returns:
int: vertical rate in feet/minutes
"""
d = util.hex2bin(data(msg))
sign = d[35] # 1 -> minus
value = util.bin2int(d[36:45]) * 32 # feet/min
roc = -1*value if sign else value
return roc
def ins_vr(msg):
"""Vertical rate messured by onbard equiments (IRS, AHRS)
Args:
msg (String): 28 bytes hexadecimal message (BDS60) string
Returns:
int: vertical rate in feet/minutes
"""
d = util.hex2bin(data(msg))
sign = d[46] # 1 -> minus
value = util.bin2int(d[47:56]) * 32 # feet/min
roc = -1*value if sign else value
return roc
def category(msg):
"""Aircraft category number
Args:
msg (string): 28 bytes hexadecimal message string
Returns:
int: category number
"""
if typecode(msg) < 1 or typecode(msg) > 4:
raise RuntimeError("%s: Not a identification message" % msg)
msgbin = util.hex2bin(msg)
return util.bin2int(msgbin[5:8])
def roll(msg):
"""Aircraft roll angle
Args:
msg (String): 28 bytes hexadecimal message (BDS50) string
Returns:
float: angle in degrees,
negative->left wing down, positive->right wing down
"""
d = util.hex2bin(data(msg))
sign = int(d[1]) # 1 -> left wing down
value = util.bin2int(d[2:11]) * 45 / 256.0 # degree
angle = -1 * value if sign else value
return round(angle, 1)
def velocity(msg):
"""Calculate the speed, heading, and vertical rate
Args:
msg (string): 28 bytes hexadecimal message string
Returns:
(int, float, int, string): speed (kt), heading (degree),
rate of climb/descend (ft/min), and speed type
('GS' for ground speed, 'AS' for airspeed)
"""
if typecode(msg) != 19:
raise RuntimeError("%s: Not a airborne velocity message" % msg)
msgbin = util.hex2bin(msg)
subtype = util.bin2int(msgbin[37:40])
if subtype in (1, 2):
v_ew_sign = util.bin2int(msgbin[45])
v_ew = util.bin2int(msgbin[46:56]) - 1 # east-west velocity
v_ns_sign = util.bin2int(msgbin[56])
v_ns = util.bin2int(msgbin[57:67]) - 1 # north-south velocity
v_we = -1*v_ew if v_ew_sign else v_ew
v_sn = -1*v_ns if v_ns_sign else v_ns
spd = math.sqrt(v_sn*v_sn + v_we*v_we) # unit in kts
hdg = math.atan2(v_we, v_sn)
hdg = math.degrees(hdg) # convert to degrees
hdg = hdg if hdg >= 0 else hdg + 360 # no negative val
tag = 'GS'
else:
hdg = util.bin2int(msgbin[46:56]) / 1024.0 * 360.0
spd = util.bin2int(msgbin[57:67])
tag = 'AS'
vr_sign = util.bin2int(msgbin[68])
vr = util.bin2int(msgbin[68:77]) # vertical rate
rocd = -1*vr if vr_sign else vr # rate of climb/descend
return int(spd), round(hdg, 1), int(rocd), tag
def altitude(msg):
"""Decode aircraft altitude
Args:
msg (string): 28 bytes hexadecimal message string
Returns:
int: altitude in feet
"""
if typecode(msg) < 9 or typecode(msg) > 18:
raise RuntimeError("%s: Not a position message" % msg)
msgbin = util.hex2bin(msg)
q = msgbin[47]
if q:
n = util.bin2int(msgbin[40:47]+msgbin[48:52])
alt = n * 25 - 1000
return alt
else:
return None
def nic(msg):
"""Calculate NIC, navigation integrity category
Args:
msg (string): 28 bytes hexadecimal message string
Returns:
int: NIC number (from 0 to 11), -1 if not applicable
"""
if typecode(msg) < 9 or typecode(msg) > 18:
raise RuntimeError("%s: Not a airborne position message" % msg)
msgbin = util.hex2bin(msg)
tc = typecode(msg)
nic_sup_b = util.bin2int(msgbin[39])
if tc in [0, 18, 22]:
nic = 0
elif tc == 17:
nic = 1
elif tc == 16:
if nic_sup_b:
nic = 3
else:
nic = 2
elif tc == 15:
nic = 4
elif tc == 14:
nic = 5
elif tc == 13:
nic = 6
elif tc == 12:
nic = 7
elif tc == 11:
if nic_sup_b:
nic = 9
else:
nic = 8
elif tc in [10, 21]:
nic = 10
elif tc in [9, 20]:
nic = 11
else:
nic = -1
return nic
def isBDS20(msg):
"""Check if a message is likely to be BDS code 2,0
Args:
msg (String): 28 bytes hexadecimal message string
Returns:
bool: True or False
"""
# status bit 1, 14, and 27
d = util.hex2bin(data(msg))
result = True
if util.bin2int(d[0:4]) != 2 or util.bin2int(d[4:8]) != 0:
result &= False
cs = callsign(msg)
if '#' in cs:
result &= False
return result
def callsign(msg):
"""Aircraft callsign
Args:
msg (String): 28 bytes hexadecimal message (BDS40) string
Returns:
string: callsign, max. 8 chars
"""
chars = '#ABCDEFGHIJKLMNOPQRSTUVWXYZ#####_###############0123456789######'
d = util.hex2bin(data(msg))
cs = ''
cs += chars[util.bin2int(d[8:14])]
cs += chars[util.bin2int(d[14:20])]
cs += chars[util.bin2int(d[20:26])]
cs += chars[util.bin2int(d[26:32])]
cs += chars[util.bin2int(d[32:38])]
cs += chars[util.bin2int(d[38:44])]
cs += chars[util.bin2int(d[44:50])]
cs += chars[util.bin2int(d[50:56])]
return cs
def isBDS40(msg):
"""Check if a message is likely to be BDS code 4,0
Args:
msg (String): 28 bytes hexadecimal message string
Returns:
bool: True or False
"""
# status bit 1, 14, and 27
d = util.hex2bin(data(msg))
result = True
result = result & checkbits(d, 1, 2, 13) \
& checkbits(d, 14, 15, 26) & checkbits(d, 27, 28, 39)
# bits 40-47 and 52-53 shall all be zero
if util.bin2int(d[39:47]) != 0:
result &= False
if util.bin2int(d[51:53]) != 0:
result &= False
return result
def test_crc_encode():
parity = util.crc("8D406B902015A678D4D220AA4BDA", encode=True)
assert util.hex2bin("AA4BDA") == parity
def test_hex2bin():
assert util.hex2bin('6E406B') == "011011100100000001101011"
def position(msg0, msg1, t0, t1):
"""Decode position from the combination of even and odd position message
131072 is 2^17, since CPR lat and lon are 17 bits each.
Args:
msg0 (string): even message (28 bytes hexadecimal string)
msg1 (string): odd message (28 bytes hexadecimal string)
t0 (int): timestamps for the even message
t1 (int): timestamps for the odd message
Returns:
(float, float): (latitude, longitude) of the aircraft
"""
if typecode(msg0) < 5 or typecode(msg0) > 18:
raise RuntimeError("%s: Not a position message" % msg0)
if typecode(msg1) < 5 or typecode(msg1) > 18:
raise RuntimeError("%s: Not a position message" % msg1)
msgbin0 = util.hex2bin(msg0)
msgbin1 = util.hex2bin(msg1)
cprlat_even = util.bin2int(msgbin0[54:71]) / 131072.0
cprlon_even = util.bin2int(msgbin0[71:88]) / 131072.0
cprlat_odd = util.bin2int(msgbin1[54:71]) / 131072.0
cprlon_odd = util.bin2int(msgbin1[71:88]) / 131072.0
air_d_lat_even = 360.0 / 60
air_d_lat_odd = 360.0 / 59
# compute latitude index 'j'
j = int(math.floor(59 * cprlat_even - 60 * cprlat_odd + 0.5))
lat_even = float(air_d_lat_even * (j % 60 + cprlat_even))
lat_odd = float(air_d_lat_odd * (j % 59 + cprlat_odd))
if lat_even >= 270:
lat_even = lat_even - 360
if lat_odd >= 270:
lat_odd = lat_odd - 360
# check if both are in the same latidude zone, exit if not
if _cprNL(lat_even) != _cprNL(lat_odd):
return None
# compute ni, longitude index m, and longitude
if (t0 > t1):
ni = _cprN(lat_even, 0)
m = math.floor(cprlon_even * (_cprNL(lat_even)-1) -
cprlon_odd * _cprNL(lat_even) + 0.5)
lon = (360.0 / ni) * (m % ni + cprlon_even)
lat = lat_even
else:
ni = _cprN(lat_odd, 1)
m = math.floor(cprlon_even * (_cprNL(lat_odd)-1) -
cprlon_odd * _cprNL(lat_odd) + 0.5)
lon = (360.0 / ni) * (m % ni + cprlon_odd)
lat = lat_odd
if lon > 180:
lon = lon - 360
return round(lat, 5), round(lon, 5)
def test_crc_encode():
parity = util.crc("8D406B902015A678D4D220AA4BDA", encode=True)
assert util.hex2bin("AA4BDA") == parity
def test_hex2bin():
assert util.hex2bin('6E406B') == "011011100100000001101011"
