AIVDM / AIVDO Sentence Creator — AIS Message Generator Online

Message TypeTalkerChannelSeq ID (multi-sentence)

Fields

Message TypeRepeat Indicator (0–3)MMSI (9 digits)Navigation StatusRate of Turn (raw −128..127)SOG (knots, 0–102.2)102.3 → not availablePosition AccuracyLongitude (°)Latitude (°)COG (°, 0.0–359.9)True Heading (0–359, 511=N/A)Time Stamp (0–63)60=N/A, 61=manual, 62=dead-reckoning, 63=inoperativeManeuver IndicatorRAIM FlagRadio Status (19 bits)

NMEA sentence

!AIVDM,1,1,,B,139Lg1hP1sP:P=pKu?p3Jjip0000,0*72

Round-trip validation

✅ encode → decode matches

NMEA checksumvalid
Bit payload168 bits
Message Type1
MMSI211234567

Binary payload

168 bits · fillBits 0

000001 000011 001001 011100 101111 000001 110000 100000 000001 111011 100000 001010 100000 001101 111000 011011 111101 001111 111000 000011 011010 110010 110001 111000 000000 000000 000000 000000

Field breakdown

Field	Bits	Value	Binary
Message Type	6	1	000001
Repeat Indicator	2	0	00
MMSI	30	211234567	001100100101110010111100000111
Navigation Status	4	0	0000
Rate of Turn	8	-128	10000000
SOG (raw)	10	123	0001111011
Position Accuracy	1	1	1
Longitude (raw)	28	1376700	0000000101010000000110111100
Latitude (raw)	27	29315040	001101111110100111111100000
COG (raw)	12	875	001101101011
True Heading	9	88	001011000
Time Stamp	6	60	111100
Maneuver Indicator	2	0	00
Spare	3	0	000
RAIM Flag	1	0	0
Radio Status	19	0	0000000000000000000

Other formats

Python bytes

b'!AIVDM,1,1,,B,139Lg1hP1sP:P=pKu?p3Jjip0000,0*72\r\n'

JavaScript string

'!AIVDM,1,1,,B,139Lg1hP1sP:P=pKu?p3Jjip0000,0*72\r\n'

Hex dump

21 41 49 56 44 4d 2c 31 2c 31 2c 2c 42 2c 31 33 39 4c 67 31 68 50 31 73 50 3a 50 3d 70 4b 75 3f 70 33 4a 6a 69 70 30 30 30 30 2c 30 2a 37 32 0d 0a

Batch generator (Type 1)

Count (1–100)MMSI modeFixed MMSICOG modeMin LatitudeMax LatitudeMin LongitudeMax LongitudeMin SOG (kt)Max SOG (kt)Fixed COG (°)

Reference tables

Navigation status

0	Under way using engine
1	At anchor
2	Not under command
3	Restricted manoeuvrability
4	Constrained by draught
5	Moored
6	Aground
7	Engaged in fishing
8	Under way sailing
9	Reserved (HSC)
10	Reserved (WIG)
11	Towing astern
12	Pushing ahead
13	Reserved
14	AIS-SART / MOB / EPIRB
15	Not defined (default)

EPFD type

0	Undefined
1	GPS
2	GLONASS
3	Combined GPS/GLONASS
4	Loran-C
5	Chayka
6	Integrated Navigation
7	Surveyed
8	Galileo

Aid type (Type 21)

0	Default, not specified
1	Reference point
2	RACON
3	Fixed structure off shore
4	Spare
5	Light, without sectors
6	Light, with sectors
7	Leading Light Front
8	Leading Light Rear
9	Beacon, Cardinal N
10	Beacon, Cardinal E
11	Beacon, Cardinal S
12	Beacon, Cardinal W
13	Beacon, Port hand
14	Beacon, Starboard hand
15	Beacon, Preferred Port
16	Beacon, Preferred Starboard
17	Beacon, Isolated danger
18	Beacon, Safe water
19	Beacon, Special mark
20	Cardinal Mark N
21	Cardinal Mark E
22	Cardinal Mark S
23	Cardinal Mark W
24	Port hand Mark
25	Starboard hand Mark
26	Preferred Channel Port hand
27	Preferred Channel Starboard hand
28	Isolated danger
29	Safe Water
30	Special Mark
31	Light Vessel / LANBY / Rigs

Ship type

0	Not available
20	WIG (Wing in ground)
21	WIG, Hazardous A
22	WIG, Hazardous B
23	WIG, Hazardous C
24	WIG, Hazardous D
30	Fishing
31	Towing
32	Towing (large)
33	Dredging or underwater ops
34	Diving ops
35	Military ops
36	Sailing
37	Pleasure craft
40	HSC (High-speed craft)
41	HSC, Hazardous A
42	HSC, Hazardous B
43	HSC, Hazardous C
44	HSC, Hazardous D
49	HSC, no info
50	Pilot vessel
51	Search and rescue
52	Tug
53	Port tender
54	Anti-pollution
55	Law enforcement
58	Medical transport
59	Noncombatant ship
60	Passenger
61	Passenger, Hazardous A
62	Passenger, Hazardous B
63	Passenger, Hazardous C
64	Passenger, Hazardous D
69	Passenger, no info
70	Cargo
71	Cargo, Hazardous A
72	Cargo, Hazardous B
73	Cargo, Hazardous C
74	Cargo, Hazardous D
79	Cargo, no info
80	Tanker
81	Tanker, Hazardous A
82	Tanker, Hazardous B
83	Tanker, Hazardous C
84	Tanker, Hazardous D
89	Tanker, no info
90	Other
99	Other, no info

Message type families

1, 2, 3 — Class A position report
4 — Base station report
5 — Static & voyage data
18, 19 — Class B position
21 — Aid to Navigation
24 — Class B static (Part A + B)

Special sentinel values

SOG raw 1023 → not available
COG raw 3600 → not available
Heading 511 → not available
Lon > 180 / Lat > 90 → not available
Timestamp 60..63 → manual / N/A / DR / inop
ROT raw −128 → not available

AIS Decoder →AIS → GeoJSON →MMSI Decoder →

About AIVDM / AIVDO Sentence Creator

The AIVDM / AIVDO Sentence Creator builds and encodes complete NMEA AIS sentences from the fields you enter. Choose a message type — Class A position reports (Types 1, 2, 3), base station reports (Type 4), static and voyage data (Type 5), Class B reports (Type 18), aids to navigation (Type 21) and Class B static data (Type 24 Parts A and B) — fill in values like MMSI and coordinates, and get a ready-to-use sentence with the correct 6-bit payload, fill bits and NMEA checksum.

It is made for AIS developers, marine software testers, equipment integrators and students who need valid sample sentences without a live transmitter. Pick the AIVDM or AIVDO talker and channel A or B, generate single or batch output, and inspect the bit-field breakdown. It is completely free and runs entirely in your browser, so every MMSI and position you enter stays on your machine and is never uploaded.

How to use

Select the AIS message type you want to build (Type 1-5, 18, 21 or 24).

Enter the field values such as MMSI, position, speed and voyage data.

Choose the AIVDM or AIVDO talker and radio channel A or B.

Copy the generated sentence, complete with payload, fill bits and checksum.

Review the bit-field breakdown and round-trip check to confirm encoding.

Frequently asked questions

Which AIS message types can I create?

You can build Class A position reports (Types 1, 2 and 3), base station reports (Type 4), static and voyage data (Type 5), Class B position reports (Type 18), aids to navigation (Type 21) and Class B static data (Type 24, Parts A and B).

What is the difference between AIVDM and AIVDO?

AIVDM sentences report data received from other vessels and stations, while AIVDO sentences carry your own ship's transmitted data. You can switch the talker with a single setting before generating.

Does the tool handle multipart sentences and fill bits?

Yes. Longer payloads that exceed a single sentence are automatically split into numbered fragments, and the correct fill-bit count is placed on the final fragment along with a valid checksum.

Is my data uploaded anywhere?

No. The tool is free and runs entirely client-side in your browser, so every MMSI, coordinate and field value you enter stays on your device and is never sent to a server.

Can I trust the encoded output?

Each sentence is encoded per the ITU-R M.1371 6-bit scheme, and a round-trip check decodes the result back to verify the checksum, message type and MMSI match your input.

Field

Bits

Value

Binary

Message Type

000001

Repeat Indicator

MMSI

211234567

001100100101110010111100000111

Navigation Status

0000

Rate of Turn

-128

10000000

SOG (raw)

123

0001111011

Position Accuracy

Longitude (raw)

1376700

0000000101010000000110111100

Latitude (raw)

29315040

001101111110100111111100000

COG (raw)

875

001101101011

True Heading

001011000

Time Stamp

111100

Maneuver Indicator

Spare

000

RAIM Flag

Radio Status

0000000000000000000

About AIVDM / AIVDO Sentence Creator

How to use

Select the AIS message type you want to build (Type 1-5, 18, 21 or 24).

Enter the field values such as MMSI, position, speed and voyage data.

Choose the AIVDM or AIVDO talker and radio channel A or B.

Copy the generated sentence, complete with payload, fill bits and checksum.

Review the bit-field breakdown and round-trip check to confirm encoding.

Frequently asked questions

Which AIS message types can I create?

What is the difference between AIVDM and AIVDO?

AIVDM sentences report data received from other vessels and stations, while AIVDO sentences carry your own ship's transmitted data. You can switch the talker with a single setting before generating.

Does the tool handle multipart sentences and fill bits?

Yes. Longer payloads that exceed a single sentence are automatically split into numbered fragments, and the correct fill-bit count is placed on the final fragment along with a valid checksum.

Is my data uploaded anywhere?

No. The tool is free and runs entirely client-side in your browser, so every MMSI, coordinate and field value you enter stays on your device and is never sent to a server.

Can I trust the encoded output?

Each sentence is encoded per the ITU-R M.1371 6-bit scheme, and a round-trip check decodes the result back to verify the checksum, message type and MMSI match your input.

Fields

NMEA sentence

Round-trip validation

Binary payload

Field breakdown

Navigation status

EPFD type

Aid type (Type 21)

Ship type

Message type families

Special sentinel values

Was this tool useful?

About AIVDM / AIVDO Sentence Creator

How to use

Features

Frequently asked questions

Related tools

AIS Message Decoder

AIS Message Encoder

NMEA 0183 Sentence Parser

Fields

NMEA sentence

Round-trip validation

Binary payload

Field breakdown

Navigation status

EPFD type

Aid type (Type 21)

Ship type

Message type families

Special sentinel values

Was this tool useful?

About AIVDM / AIVDO Sentence Creator

How to use

Features

Frequently asked questions

Related tools

AIS Message Decoder

AIS Message Encoder

NMEA 0183 Sentence Parser