pyModeS978 2026.7.1

Pure-Python decoder for UAT (978 MHz) frames

pyModeS978

A pure-Python decoder for UAT (978 MHz) frames — the sibling protocol to 1090 MHz ADS-B. This project builds on the excellent work of pyModeS, the Python library this one takes its name, API shape, and field-naming conventions from. pyModeS has no UAT support and no Python UAT decoder exists elsewhere, so this library implements the frame layout from scratch. Wherever possible, fields with like-for-like meaning are mapped 1:1, so using this library should feel familiar — often a drop-in replacement — for anyone already working with pyModeS.

Install

pip install pyModeS978

Usage

import pyModeS978

raw = "-08A042FF27EF018BF51C59C9079A0C40EB1019073F5D440B8EA5E280005F30000000"
result = pyModeS978.decode(raw)   # dict | None

raw is accepted with or without the dump978-fa direction prefix (- = downlink, + = uplink); trailing ;metadata is stripped if present. If the prefix is omitted, direction is inferred from byte length instead. Uplink frames (FIS-B weather/NOTAM ground broadcasts) always decode to None — they carry no traffic data, and 1090 traffic rebroadcast to UAT receivers (TIS-B/ADS-R) already arrives as a downlink frame, distinguished via address_qualifier. None here is expected behavior, not an error — see Error Handling for what actually raises.

Fields not applicable to a given frame's payload_type are present with value None, never omitted. Keys are sorted alphabetically, so a specific field is easy to find in printed output. Real example output (a long-frame ADS-B message: HDR + State Vector + Mode Status + AUX SV):

{
    'address_qualifier': AddressQualifier.ADSB_ICAO,
    'airground_state': AirgroundState.AIRBORNE_SUBSONIC,
    'altitude': 34875,
    'altitude_secondary': 37050,
    'altitude_secondary_type': AltitudeSource.GNSS,
    'altitude_type': AltitudeSource.BARO,
    'atc_services': False,
    'callsign': 'N116FE',
    'category': EmitterCategory.MEDIUM,
    'emergency_state': Emergency.NO_EMERGENCY,
    'es_in': True,
    'geo_minus_baro': 2175,
    'groundspeed': 486,
    'gva': 2,
    'heading': None,
    'heading_type': None,
    'icao': 'A042FF',
    'ident_active': False,
    'latitude': 28.078308,
    'length': None,
    'longitude': -81.592412,
    'magnetic_heading': None,
    'nac_p': 10,
    'nac_v': 2,
    'nic': 9,
    'nic_baro': True,
    'nic_supplement_a': False,
    'payload_type': PayloadType.LONG,
    'position_accuracy_epu_m': 10,
    'position_accuracy_vepu_m': 15,
    'position_containment_radius_m': None,
    'position_offset': None,
    'position_vpl_m': None,
    'sda': 2,
    'sil': 3,
    'sil_probability_horizontal': 1e-07,
    'sil_probability_vertical': 2e-07,
    'sil_supplement': SILSupplement.PER_HOUR,
    'single_antenna': False,
    'squawk': None,
    'tcas_operational': True,
    'tcas_ra_active': False,
    'tisb_site_id': None,
    'track': 357.3,
    'transmit_mso': 35,
    'uat_in': True,
    'utc_coupled': True,
    'velocity_accuracy_hfom_ms': 3,
    'velocity_accuracy_vfom_ms': 4.5,
    'version': 2,
    'vertical_rate': 832,
    'vertical_status': 'airborne',
    'vr_source': AltitudeSource.BARO,
    'width': None,
}

position_containment_radius_m/position_vpl_m are None here because nic=9 is only resolvable when nic_supplement_a=True — a real, expected gap in the underlying table, not a bug (see _uncertainty.py).

Fields typed as one of pyModeS978's IntEnums (see the data dictionary for the complete list, their values, and any per-field caveats) still compare/hash equal to their plain-int value.

Error Handling

Malformed input to decode() raises one of three DecodeError subclasses, rather than returning None. None is reserved for uplink frames (see Usage). DecodeError itself subclasses ValueError, so except ValueError: catches any of them:

• InvalidHexError: the input contains non-hex characters, or an odd number of hex characters.
• InvalidLengthError: the decoded input isn't 18, 34, or 432 bytes.
• DirectionMismatchError: the -/+ prefix disagrees with the direction implied by the input's byte length.

Every error type carries the original input passed to decode() as .raw, unmodified. This is useful for correlating a failure back to its input.

Data dictionary

The table below lists every field either library can return, alphabetical by field name:

• pyModeS978 Field — the field pyModeS978 returns. ❌ means that data simply isn't available from a UAT frame.
• pyModeS Equivalent — the matching field in pyModeS's 1090 decode() output. ❌ means there is not a directly comparable field in pyModeS.
• Payload Types — which payload_type values a field's block is structurally present for. — for pyModeS-only fields, since they don't exist in decode()'s output at all.
• Notes — everything else: finer per-frame conditions like ground/airborne-only, or when a field resolves to None even within an applicable payload type.

In the table below, pyModeS-only fields are inserted alphabetically as if pyModeS978 had a field of that same name, so the whole table reads as one merged, alphabetical list. Where a field's type is one of pyModeS978's IntEnums, its possible values are listed.

Two recurring patterns, noted once here instead of in every row:

• pyModeS exposes its Mode Status-equivalent capability/operational-mode bits as two raw bitfield ints (capability_class, operational_mode). UAT's smaller capability/operational-mode set made it practical to break these out into individual named booleans instead (uat_in, es_in, tcas_operational, tcas_ra_active, ident_active, atc_services).
• pyModeS's own _uncertainty.py has equivalent NIC/NACp/NACv/SIL lookup tables, but leaves calling them up to the caller. The position_accuracy_*/velocity_accuracy_*/position_containment_*/sil_probability_* fields here call the UAT equivalents automatically as part of decode(), since a single-call decode was the natural fit for how UAT frames are structured.

pyModeS978 Field	pyModeS Equivalent	Description	Payload Types	Notes
❌	acas_hybrid_surveillance	ACAS hybrid surveillance capability flag.	—	1090 only, BDS 1,0.
❌	acas_operational	Whether ACAS is operational (the data link capability report's own copy of this flag).	—	1090 only, BDS 1,0.
❌	acas_resolution_advisory	Whether ACAS resolution advisory generation is active.	—	1090 only, BDS 1,0.
❌	acas_rtca_version	Which RTCA ACAS version the equipment implements.	—	1090 only, BDS 1,0.
address_qualifier	❌	AddressQualifier enum — what kind of address icao is and where the frame came from. Values: ADSB_ICAO, NATIONAL_RESERVED, TISB_ICAO, TISB_OTHER, VEHICLE, FIXED_BEACON, RESERVED_6, RESERVED_7.	All	—
❌	aircraft_identification_capability	Whether the transponder can report aircraft identification (BDS 0,8).	—	1090 only, BDS 1,0.
airground_state	❌	AirgroundState enum — AIRBORNE_SUBSONIC, AIRBORNE_SUPERSONIC, ON_GROUND, or RESERVED.	0–10	—
❌	airspeed	Air-referenced (not ground) speed, knots — an alternative to groundspeed for some subtypes.	—	1090 only, BDS 0,9.
❌	airspeed_type	Whether airspeed is true or indicated airspeed.	—	1090 only, BDS 0,9.
altitude	altitude	Feet, from the 12-bit raw altitude code: (raw - 1) * 25 - 1000.	0–10	None if the raw altitude code is 0 (unavailable).
❌	altitude_crossing	Whether the RA commands an altitude crossing maneuver.	—	1090 only, BDS 3,0.
❌	altitude_hold_mode	Whether altitude hold mode is engaged.	—	1090 only, BDS 4,0.
altitude_secondary	❌	Feet. Whichever altitude type altitude isn't — if altitude_type is BARO, this is the GNSS altitude, and vice versa.	1, 2, 5, 6	pyModeS's geo_minus_baro is a delta between the two altitudes, not a second absolute value — see geo_minus_baro below for the delta itself. None if the raw AUX SV altitude code is 0.
altitude_secondary_type	❌	AltitudeSource enum (BARO/GNSS) — always the opposite of altitude_type.	1, 2, 5, 6	Same as altitude_secondary.
altitude_type	❌	AltitudeSource enum (BARO/GNSS) — which kind of altitude altitude is.	0–10	pyModeS infers baro-vs-GNSS from the raw ADS-B typecode instead of exposing a field. None alongside altitude when unavailable.
❌	approach_mode	Whether approach mode is engaged.	—	1090 only, BDS 4,0.
atc_services	❌	Operational mode bit — aircraft is receiving ATC services.	1, 3	Packed into pyModeS's operational_mode bitfield, not individually named there.
❌	autopilot	Whether the autopilot is engaged.	—	1090 only, BDS 6,2.
❌	baro_pressure_setting	The pilot's barometric pressure setting, millibars.	—	1090 only, BDS 4,0.
❌	baro_vertical_rate	Barometric vertical rate, feet/min.	—	1090 only, BDS 6,0.
❌	bds	Which BDS register a message decoded as (e.g. "05", "09"), resolved from typecode.	—	1090 only, DF17/18.
❌	bds_candidates	When BDS is ambiguous from typecode alone, the list of registers it might be.	—	1090 only, DF17/18.
callsign	callsign	Flight ID, base-40-decoded from Mode Status's packed character field and whitespace-stripped.	1, 3	None if this frame's field holds a squawk instead (see squawk), or is blank.
❌	capability	3-bit capability field — transponder's Mode S capability level.	—	1090 only, DF11.
❌	capability_class	Raw capability class bitfield — the packed equivalent of uat_in/es_in/tcas_operational, exposed here as individually named booleans instead.	—	1090 only, BDS 6,5 operational status report.
❌	capability_text	Human-readable decode of capability.	—	1090 only, DF11.
category	category	Aircraft/vehicle emitter category. Values: NO_INFORMATION, LIGHT, MEDIUM, MEDIUM_LARGE, MEDIUM_LARGE_HIGH_VORTEX, HEAVY, HIGHLY_MANEUVERABLE, ROTORCRAFT, RESERVED_8, GLIDER_SAILPLANE, LIGHTER_THAN_AIR, PARACHUTIST_SKYDIVER, ULTRALIGHT_HANGGLIDER_PARAGLIDER, RESERVED_13, UAV, SPACE_TRANSATMOSPHERIC, RESERVED_16, EMERGENCY_VEHICLE, SERVICE_VEHICLE, POINT_OBSTACLE, CLUSTER_OBSTACLE, LINE_OBSTACLE, RESERVED_22–RESERVED_39.	1, 3	pyModeS exposes this as a bare int; pyModeS978 names the values here for readability.
❌	common_usage_gicb_capability	Whether the transponder reports common-usage GICB capability (BDS 1,7).	—	1090 only, BDS 1,0.
❌	config	Raw configuration byte.	—	1090 only, BDS 1,0 data link capability.
❌	corrective	Whether the active RA is corrective (requires a maneuver) vs. preventive.	—	1090 only, BDS 3,0.
❌	cpr_format	CPR odd/even format flag from the raw compact position report.	—	1090 only, BDS 0,5/0,6.
❌	cpr_lat	Raw, un-decoded CPR-encoded latitude.	—	1090 only, BDS 0,5/0,6.
❌	cpr_lon	Raw, un-decoded CPR-encoded longitude.	—	1090 only, BDS 0,5/0,6.
❌	crc_valid	Whether the message's CRC checksum passed.	—	1090 only, DF17/18/20/21.
❌	cross_link_capability	Whether the transponder can support DF16 replies.	—	1090 only, DF0.
❌	df	Downlink Format — the 5-bit code identifying which of ~10 different Mode S/ADS-B message formats a 1090 reply is.	—	1090 only, always present; no UAT equivalent structurally, though payload_type serves a similar use.
❌	downlink_elm_throughput	Downlink Extended Length Message throughput capability.	—	1090 only, BDS 1,0.
❌	downlink_request	Whether the transponder has more data queued to send.	—	1090 only, DF4/5/20/21.
❌	downward_sense	Whether the RA commands a downward sense.	—	1090 only, BDS 3,0.
❌	dte_status	Data Terminal Equipment status field.	—	1090 only, BDS 1,0.
emergency_state	emergency_state	Emergency enum — emergency/priority status. Values: NO_EMERGENCY, GENERAL, MEDICAL, MINIMUM_FUEL, NO_COMMUNICATIONS, UNLAWFUL_INTERFERENCE, DOWNED_AIRCRAFT, RESERVED_7.	1, 3	pyModeS exposes this as a bare int.
❌	error	Error message text, part of pyModeS's corrupt-input error envelope for batch/pipe decode modes.	—	1090 only.
es_in	❌	Capability code — has a 1090ES receiver.	1, 3	Packed into pyModeS's capability_class bitfield, not individually named there.
❌	figure_of_merit	Confidence/quality indicator for the met report.	—	1090 only, BDS 4,4.
❌	flight_status	Raw 3-bit flight status code — alert/SPI/on-ground bits.	—	1090 only, DF4/5/20/21.
❌	flight_status_text	Human-readable decode of flight_status.	—	1090 only, DF4/5/20/21.
geo_minus_baro	geo_minus_baro	Signed delta between geometric and barometric altitude, feet — geometric - barometric, derived directly from altitude/altitude_secondary and their _type tags. Derived convenience field, not a new bit read; matches pyModeS's field name.	1, 2, 5, 6	None if either altitude is unavailable in this frame.
groundspeed	groundspeed	Knots, rounded. Airborne: √(ns² + ew²) from the N/S and E/W velocity components. Ground: a direct raw code.	0–10	None for RESERVED airground state.
gva	❌	Geometric Vertical Accuracy, 2-bit raw (0–3) — 95% accuracy bound on GNSS altitude.	1, 3	—
heading	heading	Ground-only heading, 1 decimal, from the 11-bit raw track/heading code (* 360/512).	0–10	Populated instead of track only when the ground type code says magnetic or true heading — see heading_type.
heading_type	❌	HeadingType enum (MAGNETIC/TRUE) — which kind of heading heading is.	0–10	No 1090 equivalent — added to preserve the magnetic/true distinction UAT's ground type code carries. None whenever heading is None.
❌	hrd	Horizontal Reference Direction — whether headings are referenced to true or magnetic north.	—	1090 only, BDS 6,5.
❌	humidity	Relative humidity, %.	—	1090 only, BDS 4,4.
icao	icao	24-bit address, 6 hex chars, uppercase.	All	Despite the name, not always a real ICAO address — see address_qualifier.
❌	icao_verified	Whether the extracted ICAO address was cross-checked against overlay/parity bits.	—	1090 only, DF20/21.
❌	icing	Icing intensity code.	—	1090 only, BDS 4,5.
ident_active	❌	Operational mode bit — the pilot has pressed IDENT.	1, 3	Packed into pyModeS's operational_mode bitfield, not individually named there.
❌	increased_rate	Whether the RA commands an increased climb/descent rate.	—	1090 only, BDS 3,0.
❌	indicated_airspeed	Indicated airspeed, knots.	—	1090 only, BDS 6,0.
❌	inertial_vertical_rate	Inertial (INS/IRS-derived) vertical rate, feet/min.	—	1090 only, BDS 6,0.
❌	issued_ra	Whether a resolution advisory has been issued.	—	1090 only, BDS 3,0.
latitude	latitude	Decoded position, 6 decimal places (raw * 360 / 2^24). Absolute in every frame — no CPR even/odd pairing needed, unlike 1090.	0–10	None if there's no valid fix (nic == 0 and raw lat/lon both 0).
length	❌	Aircraft length, meters, from the width/length code table.	0–10	Ground only.
❌	lnav_mode	Whether LNAV mode is engaged.	—	1090 only, BDS 6,2.
longitude	longitude	See latitude.	0–10	Same as latitude.
❌	mach	Mach number.	—	1090 only, BDS 6,0.
magnetic_heading	magnetic_heading	Degrees, 1 decimal — same value as heading when heading_type is MAGNETIC, else None. Derived convenience field, not a new bit read; matches pyModeS's field name.	0–10	Ground only.
❌	microburst	Microburst intensity code.	—	1090 only, BDS 4,5.
❌	mode_s_specific_services	Whether Mode S specific services capability is reported.	—	1090 only, BDS 1,0.
❌	mode_s_subnetwork_version	Which Mode S subnetwork version the transponder implements.	—	1090 only, BDS 1,0.
❌	movement	Raw groundspeed movement code.	—	1090 only, BDS 0,6 surface position.
❌	multiple_threat	Whether multiple simultaneous threats are being tracked.	—	1090 only, BDS 3,0.
❌	mv	Raw ACAS message field, further decoded into BDS 3,0 fields if a TCAS RA is active.	—	1090 only, DF16.
nac_p	nac_p	Navigation Accuracy Category for Position, 4-bit raw (0–15; only 0–11 defined). Resolves position_accuracy_epu_m/position_accuracy_vepu_m.	1, 3	—
nac_v	nac_v	Navigation Accuracy Category for Velocity, 3-bit raw (0–7; only 0–4 defined). Resolves velocity_accuracy_hfom_ms/velocity_accuracy_vfom_ms.	1, 3	—
nic	❌	Navigation Integrity Category, 4-bit raw (0–15) — confidence in the position fix. Combines with nic_supplement_a to resolve position_containment_radius_m/position_vpl_m.	0–10	pyModeS resolves NIC internally from typecode + supplement bits for its own uncertainty functions; the resolved number itself isn't part of its decode() output.
❌	nic_b	The single "NIC supplement B" bit carried in the raw airborne position message.	—	1090 only, BDS 0,5.
nic_baro	nic_baro	Whether the barometric altitude has been cross-checked against another source.	1, 3	bool here; pyModeS exposes it as a bare int.
nic_supplement_a	nic_supplement_a	The one NIC supplement bit UAT has (1090 has two).	1, 3	bool here; pyModeS exposes it as a bare int.
❌	no_above	Whether the RA is a "do not climb above" restriction.	—	1090 only, BDS 3,0.
❌	no_below	Whether the RA is a "do not descend below" restriction.	—	1090 only, BDS 3,0.
❌	no_left	Whether the RA is a "do not turn left" restriction (rare horizontal RA variant).	—	1090 only, BDS 3,0.
❌	no_right	Whether the RA is a "do not turn right" restriction.	—	1090 only, BDS 3,0.
❌	nuc_p	Navigation Uncertainty Category for Position — the older, pre-NIC/NACp accuracy metric BDS 0,5 also carries for backward compatibility.	—	1090 only, BDS 0,5.
❌	operational_mode	Raw operational mode bitfield — the packed equivalent of tcas_ra_active/ident_active/atc_services, exposed here as individually named booleans instead.	—	1090 only, BDS 6,5.
❌	overlay_command_capability	Whether the transponder supports the overlay command capability.	—	1090 only, BDS 1,0.
payload_type	❌	PayloadType enum, 5-bit raw — determines which blocks (State Vector/Mode Status/AUX SV) are present in this frame. Named values: SHORT, LONG, SHORT_AUX, SHORT_MS; other raw values (4–31) fall back to the plain int.	All	Serves a similar use to pyModeS's df (Downlink Format).
position_accuracy_epu_m	❌	Estimated Position Uncertainty, meters (95%), from nac_p.	1, 3	Derivable from pyModeS's own _uncertainty.py, not auto-called there.
position_accuracy_vepu_m	❌	Vertical EPU, meters (95%), from nac_p. Only defined for the two highest nac_p values.	1, 3	Derivable from pyModeS's own _uncertainty.py, not auto-called there.
position_containment_radius_m	❌	Containment radius implied by nic + nic_supplement_a. None for combinations the spec doesn't define (e.g. nic=9 is only defined when nic_supplement_a=True) — a real gap in the table, not a bug.	1, 3	Derivable from pyModeS's own _uncertainty.py, not auto-called there.
position_offset	❌	Whether the GPS antenna is offset from the nose/wingtip, per the length/width code's convention.	0–10	Ground only.
position_vpl_m	❌	Vertical Protection Limit implied by nic + nic_supplement_a. Same undefined-combination caveat as position_containment_radius_m.	1, 3	Derivable from pyModeS's own _uncertainty.py, not auto-called there.
❌	positive	Whether the RA is a positive (climb/descend) vs. vertical-speed-limit RA.	—	1090 only, BDS 3,0.
❌	ra_terminated	Whether the RA has been terminated.	—	1090 only, BDS 3,0.
❌	radio_height	Radio altimeter height, feet.	—	1090 only, BDS 4,5.
❌	raw_msg	The original raw message hex, included in the error envelope alongside error.	—	1090 only.
❌	reply_information	ACAS/Mode S transponder capability signaled in a short ACAS reply.	—	1090 only, DF0/16.
❌	roll	Roll angle, degrees.	—	1090 only, BDS 5,0 track and turn report.
sda	❌	System Design Assurance, 2-bit raw (0–3) — failure-rate classification of the transmitting equipment.	1, 3	—
❌	selected_altitude	Selected altitude.	—	1090 only, BDS 6,2 target state and status report.
❌	selected_altitude_fms	The FMS selected altitude (may differ from the MCP value).	—	1090 only, BDS 4,0.
❌	selected_altitude_mcp	The MCP/FCU selected altitude.	—	1090 only, BDS 4,0 selected vertical intention.
❌	selected_altitude_source	Which source the selected altitude came from.	—	1090 only, BDS 6,2.
❌	selected_heading	Selected heading, degrees.	—	1090 only, BDS 6,2.
❌	sense_reversal	Whether the RA commands a sense reversal.	—	1090 only, BDS 3,0.
❌	sensitivity_level	ACAS sensitivity level in use.	—	1090 only, DF0/16.
sil	sil	Source Integrity Level, 2-bit raw (0–3) — probability the reported position exceeds the NIC containment radius without alerting.	1, 3	—
sil_probability_horizontal	❌	Probability position_containment_radius_m is exceeded without alerting, from sil. Time base given by sil_supplement.	1, 3	Derivable from pyModeS's own _uncertainty.py, not auto-called there.
sil_probability_vertical	❌	Probability position_vpl_m is exceeded without alerting, from sil. Same time-base caveat.	1, 3	Derivable from pyModeS's own _uncertainty.py, not auto-called there.
sil_supplement	sil_supplement	PER_HOUR or PER_SAMPLE — the time base sil's probabilities apply to, not a different probability table.	1, 3	pyModeS exposes this as a bare int.
single_antenna	❌	Whether the transmitter uses a single antenna (vs. antenna diversity).	1, 3	—
squawk	squawk	Mode 3/A squawk code. A CSID flag in the same raw bits as callsign picks whether this field is a callsign or a squawk — UAT has no DF 5/21 equivalent, so this is the only source of squawk.	1, 3	Mutually exclusive with callsign.
❌	squitter_capability	Extended squitter capability flag.	—	1090 only, BDS 1,0.
❌	static_air_temperature	Static air temperature, °C.	—	1090 only, BDS 4,4.
❌	static_pressure	Static air pressure, hPa.	—	1090 only, BDS 4,4.
❌	subtype	3-bit subtype — airborne vs. surface, GNSS vs. air-referenced groundspeed.	—	1090 only, BDS 0,9.
❌	supported_bds	Which BDS registers this transponder supports.	—	1090 only, BDS 1,7 GICB capability report.
❌	surveillance_identifier_code	Surveillance identifier code capability flag.	—	1090 only, BDS 1,0.
❌	surveillance_status	2-bit surveillance status field.	—	1090 only, BDS 0,5.
❌	target_altitude_source	Which source (MCP/FMS/etc.) selected_altitude_mcp/selected_altitude_fms came from.	—	1090 only, BDS 4,0.
tcas_operational	tcas_operational	Capability code — TCAS/ACAS is installed and operational.	1, 3	Also packed into pyModeS's capability_class bitfield.
tcas_ra_active	❌	Operational mode bit — a TCAS/ACAS resolution advisory is currently active.	1, 3	1090's closest concept is the multi-field BDS 3,0 ACAS RA broadcast (issued_ra, corrective, etc.), not a single boolean.
❌	threat_altitude	The threat aircraft's altitude, when identified by altitude/bearing/range instead.	—	1090 only, BDS 3,0.
❌	threat_bearing	The threat aircraft's bearing, degrees.	—	1090 only, BDS 3,0.
❌	threat_icao	The threat aircraft's ICAO address, when threat_type_indicator says ICAO-identified.	—	1090 only, BDS 3,0.
❌	threat_range	The threat aircraft's range, nautical miles.	—	1090 only, BDS 3,0.
❌	threat_type_indicator	Whether the threat is identified by ICAO address or by altitude/bearing/range.	—	1090 only, BDS 3,0 ACAS RA broadcast.
tisb_site_id	❌	Ground station site ID.	0–10	TIS-B frames only — same 4 raw bits as utc_coupled, reinterpreted per address_qualifier.
track	track	Track over ground, 1 decimal. Airborne: atan2 of the N/S and E/W velocity components. Ground: a direct raw code.	0–10	Airborne: always this field (never heading); ground: only when the type code says "track" rather than heading.
❌	track_rate	Rate of turn, degrees/second.	—	1090 only, BDS 5,0.
❌	track_status	Track validity bit.	—	1090 only, BDS 0,6 surface position.
transmit_mso	❌	Message Start Opportunity slot the transmitter used — a radio-layer detail, not aircraft state.	1, 3	—
❌	transponder_level5	Whether the transponder is Level 5 (Enhanced Surveillance) capable.	—	1090 only, BDS 1,0.
❌	true_airspeed	True airspeed, knots.	—	1090 only, BDS 5,0.
❌	true_track	True track angle, degrees.	—	1090 only, BDS 5,0.
❌	turbulence	Turbulence intensity code.	—	1090 only, BDS 4,4.
❌	typecode	ADS-B typecode (bits 33–37 of DF17/18) — which BDS register/subtype a message carries.	—	1090 only, DF17/18; no UAT equivalent structurally, though payload_type serves a similar use.
uat_in	❌	Capability code — has a UAT receiver.	1, 3	Packed into pyModeS's capability_class bitfield, not individually named there.
❌	uplink_elm_throughput	Uplink Extended Length Message throughput capability.	—	1090 only, BDS 1,0.
utc_coupled	❌	Whether the frame's time reference is UTC-coupled.	0–10	Native ADS-B (non-TIS-B address_qualifier) only.
❌	utility_message	IIS/IDS sub-field for interrogator identification.	—	1090 only, DF4/5/20/21.
velocity_accuracy_hfom_ms	❌	Horizontal Figure of Merit for velocity, m/s, from nac_v.	1, 3	Derivable from pyModeS's own _uncertainty.py, not auto-called there.
velocity_accuracy_vfom_ms	❌	Vertical Figure of Merit for velocity, m/s, from nac_v.	1, 3	Derivable from pyModeS's own _uncertainty.py, not auto-called there.
version	version	ADS-B/MOPS version the transmitting equipment implements, 3-bit raw.	1, 3	—
vertical_rate	vertical_rate	Feet/min, signed, from the 11-bit raw vertical rate code.	0–10	Airborne only — None on the ground (those bits hold aircraft dimensions instead).
vertical_status	vertical_status	"airborne" or "on-ground", matching pyModeS's exact strings — derived from airground_state (both AIRBORNE_SUBSONIC/AIRBORNE_SUPERSONIC map to "airborne"). Derived convenience field, not a new bit read.	0–10	None for RESERVED airground state (no pyModeS equivalent for that state).
❌	vnav_mode	Whether VNAV mode is engaged.	—	1090 only, BDS 4,0.
vr_source	vr_source	BARO or GNSS — which kind of altitude vertical_rate is derived from. Same values as pyModeS's own "BARO"/"GNSS" strings, matched exactly.	0–10	Airborne only; pyModeS exposes this as a bare str.
❌	wake_vortex	Human-readable wake turbulence category text, derived from category + typecode.	—	1090 only, BDS 0,8.
width	❌	Aircraft width, meters, from the width/length code table.	0–10	Ground only.
❌	wind_direction	Wind direction, degrees.	—	1090 only, BDS 4,4.
❌	wind_shear	Wind shear intensity code.	—	1090 only, BDS 4,5 met hazard report.
❌	wind_speed	Wind speed, knots.	—	1090 only, BDS 4,4 met routine report.

Versioning & releases

Versions are calendar-based, YYYY.M.b (year, month, per-month release count — no leading zeros, e.g. 2026.7.1), matching the convention used across other BrentIO repos. The version isn't stored in a source file at all: pyproject.toml declares it dynamic, and hatch-vcs derives it from the git tag at build time. An untagged install (e.g. straight off main) falls back to a 0.1.devN+g<hash> style dev version.

Releases are cut via the 🚀 Release GitHub Actions workflow (workflow_dispatch, takes a version input matching the format above), which validates the version, tags main, and creates a GitHub Release.

License

MIT — see LICENSE.