# ------------------------------------------
# BDS 5,3
# Air-referenced state vector
# ------------------------------------------
from pyModeS import common
[docs]def is53(msg):
"""Check if a message is likely to be BDS code 5,3
(Air-referenced state vector)
Args:
msg (str): 28 hexdigits string
Returns:
bool: True or False
"""
if common.allzeros(msg):
return False
d = common.hex2bin(common.data(msg))
# status bit 1, 13, 24, 34, 47
if common.wrongstatus(d, 1, 3, 12):
return False
if common.wrongstatus(d, 13, 14, 23):
return False
if common.wrongstatus(d, 24, 25, 33):
return False
if common.wrongstatus(d, 34, 35, 46):
return False
if common.wrongstatus(d, 47, 49, 56):
return False
ias = ias53(msg)
if ias is not None and ias > 500:
return False
mach = mach53(msg)
if mach is not None and mach > 1:
return False
tas = tas53(msg)
if tas is not None and tas > 500:
return False
vr = vr53(msg)
if vr is not None and abs(vr) > 8000:
return False
return True
[docs]def hdg53(msg):
"""Magnetic heading, BDS 5,3 message
Args:
msg (str): 28 hexdigits string
Returns:
float: angle in degrees to true north (from 0 to 360)
"""
d = common.hex2bin(common.data(msg))
if d[0] == "0":
return None
sign = int(d[1]) # 1 -> west
value = common.bin2int(d[2:12])
if sign:
value = value - 1024
hdg = value * 90.0 / 512.0 # degree
# convert from [-180, 180] to [0, 360]
if hdg < 0:
hdg = 360 + hdg
return round(hdg, 3)
[docs]def ias53(msg):
"""Indicated airspeed, DBS 5,3 message
Args:
msg (str): 28 hexdigits
Returns:
int: indicated arispeed in knots
"""
d = common.hex2bin(common.data(msg))
if d[12] == "0":
return None
ias = common.bin2int(d[13:23]) # knots
return ias
[docs]def mach53(msg):
"""MACH number, DBS 5,3 message
Args:
msg (str): 28 hexdigits
Returns:
float: MACH number
"""
d = common.hex2bin(common.data(msg))
if d[23] == "0":
return None
mach = common.bin2int(d[24:33]) * 0.008
return round(mach, 3)
[docs]def tas53(msg):
"""Aircraft true airspeed, BDS 5,3 message
Args:
msg (str): 28 hexdigits
Returns:
float: true airspeed in knots
"""
d = common.hex2bin(common.data(msg))
if d[33] == "0":
return None
tas = common.bin2int(d[34:46]) * 0.5 # kts
return round(tas, 1)
[docs]def vr53(msg):
"""Vertical rate
Args:
msg (str): 28 hexdigits (BDS60) string
Returns:
int: vertical rate in feet/minutes
"""
d = common.hex2bin(common.data(msg))
if d[46] == "0":
return None
sign = int(d[47]) # 1 -> negative value, two's complement
value = common.bin2int(d[48:56])
if value == 0 or value == 255: # all zeros or all ones
return 0
value = value - 256 if sign else value
roc = value * 64 # feet/min
return roc