AIS - AUTOMATIC IDENTIFICATION SYSTEM | EXAM QUESTIONS
AND CORRECT ANSWERS | VERIFIED MARITIME NAVIGATION
LATEST VERSION 2026/2027
Automatic Identification System - AIS
1. Q: What does AIS stand for? ANSWER Automatic Identification
System.
2. Q: What is the primary purpose of AIS? ANSWER To improve
maritime safety and collision avoidance.
3. Q: What type of system is AIS? ANSWER An automated tracking
system.
4. Q: On what frequency does AIS primarily operate? ANSWER VHF
(Very High Frequency).
5. Q: What are the two dedicated AIS channels? ANSWER AIS 1
(161.975 MHz) and AIS 2 (162.025 MHz).
6. Q: What are the ITU channel designations for AIS 1 and AIS 2?
ANSWER 87B and 88B.
7. Q: What modulation does AIS use? ANSWER GMSK (Gaussian
Minimum Shift Keying).
8. Q: What is the data rate of AIS? ANSWER 9600 bits per second.
9. Q: What bandwidth does AIS use per channel? ANSWER 25 kHz.
10. Q: Which IMO convention mandates AIS carriage? ANSWER
SOLAS (Safety of Life at Sea).
,11. Q: Under which SOLAS chapter is AIS required? ANSWER
Chapter V.
12. Q: What is the communication protocol used by AIS?
ANSWER TDMA (Time Division Multiple Access).
13. Q: What does TDMA stand for? ANSWER Time Division
Multiple Access.
14. Q: How many time slots are in one AIS frame? ANSWER
2250.
15. Q: How long is one AIS frame? ANSWER 60 seconds.
16. Q: How long is one AIS time slot? ANSWER 26.67
milliseconds.
17. Q: What access scheme is primarily used by Class A AIS?
ANSWER SOTDMA (Self-Organizing TDMA).
18. Q: What does SOTDMA stand for? ANSWER Self-Organizing
Time Division Multiple Access.
19. Q: What access scheme is primarily used by Class B AIS?
ANSWER CSTDMA (Carrier Sense TDMA).
20. Q: What does CSTDMA stand for? ANSWER Carrier Sense
Time Division Multiple Access.
21. Q: What is ITDMA? ANSWER Incremental Time Division
Multiple Access.
22. Q: When is ITDMA used? ANSWER For reporting intervals
that change or for initial station logon.
23. Q: What is RATDMA? ANSWER Random Access Time Division
Multiple Access.
24. Q: What is the nominal reporting interval for a Class A ship at
anchor? ANSWER 3 minutes.
25. Q: What is the reporting interval for a Class A ship at anchor
moving faster than 3 knots? ANSWER 10 seconds.
26. Q: What is the reporting interval for a Class A ship moving 0-
14 knots? ANSWER 10 seconds.
, 27. Q: What is the reporting interval for a Class A ship moving 0-
14 knots while changing course? ANSWER 3.33 seconds.
28. Q: What is the reporting interval for a Class A ship moving 14-
23 knots? ANSWER 6 seconds.
29. Q: What is the reporting interval for a Class A ship moving 14-
23 knots while changing course? ANSWER 2 seconds.
30. Q: What is the reporting interval for a Class A ship moving
>23 knots? ANSWER 2 seconds.
31. Q: What is the reporting interval for a Class A ship moving
>23 knots while changing course? ANSWER 2 seconds.
32. Q: What is the default reporting interval for a Class B SO
(Safety-Oriented) ship at rest? ANSWER 3 minutes.
33. Q: What is the reporting interval for a Class B SO ship moving
<2 knots? ANSWER 3 minutes.
34. Q: What is the reporting interval for a Class B SO ship moving
2-14 knots? ANSWER 30 seconds.
35. Q: What is the reporting interval for a Class B SO ship moving
14-23 knots? ANSWER 15 seconds.
36. Q: What is the reporting interval for a Class B SO ship moving
>23 knots? ANSWER 5 seconds.
37. Q: What is the reporting interval for a Class B CS (Carrier
Sense) ship at rest? ANSWER 3 minutes.
38. Q: What is the reporting interval for a Class B CS ship moving
<2 knots? ANSWER 3 minutes.
39. Q: What is the reporting interval for a Class B CS ship moving
>2 knots? ANSWER 30 seconds.
40. Q: What does MMSI stand for? ANSWER Maritime Mobile
Service Identity.
41. Q: How many digits are in an MMSI? ANSWER 9.
42. Q: What do the first three digits of an MMSI represent?
ANSWER The MID (Maritime Identification Digits), indicating the
country of flag.
AND CORRECT ANSWERS | VERIFIED MARITIME NAVIGATION
LATEST VERSION 2026/2027
Automatic Identification System - AIS
1. Q: What does AIS stand for? ANSWER Automatic Identification
System.
2. Q: What is the primary purpose of AIS? ANSWER To improve
maritime safety and collision avoidance.
3. Q: What type of system is AIS? ANSWER An automated tracking
system.
4. Q: On what frequency does AIS primarily operate? ANSWER VHF
(Very High Frequency).
5. Q: What are the two dedicated AIS channels? ANSWER AIS 1
(161.975 MHz) and AIS 2 (162.025 MHz).
6. Q: What are the ITU channel designations for AIS 1 and AIS 2?
ANSWER 87B and 88B.
7. Q: What modulation does AIS use? ANSWER GMSK (Gaussian
Minimum Shift Keying).
8. Q: What is the data rate of AIS? ANSWER 9600 bits per second.
9. Q: What bandwidth does AIS use per channel? ANSWER 25 kHz.
10. Q: Which IMO convention mandates AIS carriage? ANSWER
SOLAS (Safety of Life at Sea).
,11. Q: Under which SOLAS chapter is AIS required? ANSWER
Chapter V.
12. Q: What is the communication protocol used by AIS?
ANSWER TDMA (Time Division Multiple Access).
13. Q: What does TDMA stand for? ANSWER Time Division
Multiple Access.
14. Q: How many time slots are in one AIS frame? ANSWER
2250.
15. Q: How long is one AIS frame? ANSWER 60 seconds.
16. Q: How long is one AIS time slot? ANSWER 26.67
milliseconds.
17. Q: What access scheme is primarily used by Class A AIS?
ANSWER SOTDMA (Self-Organizing TDMA).
18. Q: What does SOTDMA stand for? ANSWER Self-Organizing
Time Division Multiple Access.
19. Q: What access scheme is primarily used by Class B AIS?
ANSWER CSTDMA (Carrier Sense TDMA).
20. Q: What does CSTDMA stand for? ANSWER Carrier Sense
Time Division Multiple Access.
21. Q: What is ITDMA? ANSWER Incremental Time Division
Multiple Access.
22. Q: When is ITDMA used? ANSWER For reporting intervals
that change or for initial station logon.
23. Q: What is RATDMA? ANSWER Random Access Time Division
Multiple Access.
24. Q: What is the nominal reporting interval for a Class A ship at
anchor? ANSWER 3 minutes.
25. Q: What is the reporting interval for a Class A ship at anchor
moving faster than 3 knots? ANSWER 10 seconds.
26. Q: What is the reporting interval for a Class A ship moving 0-
14 knots? ANSWER 10 seconds.
, 27. Q: What is the reporting interval for a Class A ship moving 0-
14 knots while changing course? ANSWER 3.33 seconds.
28. Q: What is the reporting interval for a Class A ship moving 14-
23 knots? ANSWER 6 seconds.
29. Q: What is the reporting interval for a Class A ship moving 14-
23 knots while changing course? ANSWER 2 seconds.
30. Q: What is the reporting interval for a Class A ship moving
>23 knots? ANSWER 2 seconds.
31. Q: What is the reporting interval for a Class A ship moving
>23 knots while changing course? ANSWER 2 seconds.
32. Q: What is the default reporting interval for a Class B SO
(Safety-Oriented) ship at rest? ANSWER 3 minutes.
33. Q: What is the reporting interval for a Class B SO ship moving
<2 knots? ANSWER 3 minutes.
34. Q: What is the reporting interval for a Class B SO ship moving
2-14 knots? ANSWER 30 seconds.
35. Q: What is the reporting interval for a Class B SO ship moving
14-23 knots? ANSWER 15 seconds.
36. Q: What is the reporting interval for a Class B SO ship moving
>23 knots? ANSWER 5 seconds.
37. Q: What is the reporting interval for a Class B CS (Carrier
Sense) ship at rest? ANSWER 3 minutes.
38. Q: What is the reporting interval for a Class B CS ship moving
<2 knots? ANSWER 3 minutes.
39. Q: What is the reporting interval for a Class B CS ship moving
>2 knots? ANSWER 30 seconds.
40. Q: What does MMSI stand for? ANSWER Maritime Mobile
Service Identity.
41. Q: How many digits are in an MMSI? ANSWER 9.
42. Q: What do the first three digits of an MMSI represent?
ANSWER The MID (Maritime Identification Digits), indicating the
country of flag.
