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Python Mode-S Decoder

Project description

Python library for Mode-S message decoding. Two separate methods are implemented to decode the following messages:

  • Automatic Dependent Surveillance - Broadcast (ADS-B) (DF17)
    • aircraft information that contains: ICAO address, position, altitude, velocity (ground speed), callsign, etc.
  • Mode-S Enhanced Surveillance (EHS) (DF20 and DF21)
    • additional information in response to SSR interrogation, such as: true airspeed, indicated airspeed, mach number, track angle, heading, roll angle, etc.

A detailed manual on Mode-S decoding is published by the author, at:

Source code

Checkout and contribute to this open source project at:

API documentation at:


Checkout source code, or install using pip:

pip install pyModeS


import pyModeS as pms

Common function for Mode-S message:

pms.df(msg)                 # Downlink Format
pms.crc(msg, encode=False)  # Perform CRC or generate parity bit

pms.hex2bin(str)    # Convert hexadecimal string to binary string
pms.bin2int(str)    # Convert binary string to integer
pms.hex2int(str)    # Convert hexadecimal string to integer

Core functions for ADS-B decoding:


pms.adsb.position(msg_even, msg_odd, t_even, t_odd, lat_ref=None, lon_ref=None)
pms.adsb.airborne_position(msg_even, msg_odd, t_even, t_odd)
pms.adsb.surface_position(msg_even, msg_odd, t_even, t_odd, lat_ref, lon_ref)

pms.adsb.position_with_ref(msg, lat_ref, lon_ref)
pms.adsb.airborne_position_with_ref(msg, lat_ref, lon_ref)
pms.adsb.surface_position_with_ref(msg, lat_ref, lon_ref)


Hint: When you have a fix position of the aircraft, it is convenient to use `position_with_ref()` method to decode with only one position message (either odd or even). This works with both airborne and surface position messages. But the reference position shall be with in 180NM (airborne) or 45NM (surface) of the true position.

Core functions for EHS decoding:

pms.ehs.icao(msg)       # ICAO address
pms.ehs.BDS(msg)        # Comm-B Data Selector Version

# for BDS version 2,0
pms.ehs.callsign(msg)   # Aircraft callsign

# for BDS version 4,0
pms.ehs.alt_mcp(msg)    # MCP/FCU selected altitude (ft)
pms.ehs.alt_fms(msg)    # FMS selected altitude (ft)
pms.ehs.alt_pbaro(msg)  # Barometric pressure (mb)

# for BDS version 5,0
pms.ehs.roll(msg)       # roll angle (deg)
pms.ehs.track(msg)      # track angle (deg)         # ground speed (kt)
pms.ehs.rtrack(msg)     # track angle rate (deg/sec)
pms.ehs.tas(msg)        # true airspeed (kt)

# for BDS version 6,0
pms.ehs.heading(msg)    # heading (deg)
pms.ehs.ias(msg)        # indicated airspeed (kt)
pms.ehs.mach(msg)       # MACH number
pms.ehs.baro_vr(msg)    # barometric altitude rate (ft/min)
pms.ehs.ins_vr(msg)     # inertial vertical speed (ft/min)


To run tests, run the following commands: ` $ tox `

Project details

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Filename, size & hash SHA256 hash help File type Python version Upload date
pyModeS-1.0.8-py2-none-any.whl (13.3 kB) Copy SHA256 hash SHA256 Wheel py2
pyModeS-1.0.8-py2.py3-none-any.whl (13.3 kB) Copy SHA256 hash SHA256 Wheel py2.py3

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