AIS

Question 1

1. What does SOTDMA stand for? (6)

Answer 1

Self-Organising Time Division Multiple Access

Question 2

2. What is the difference between a class A and a class B vessel? (4)

Answer 2

Class A is a vessel which it is mandatory to have AIS fitted to (commercial vessels over 3OOGT, cargo vessel >500GT, all passengers vessels). Class B is a non~mandatory fit vessel, vessels such as Fishing, leisure craft which have class B AIS equipment fitted

Question 3

3. State the three different types of information that is broadcasted (6)

Answer 3

1. Static
2. Dynamic
3. Voyage Related

Question 4

4. How frequently is each of the above transmitted? (6)

Answer 4

1. Every 6 minutes or on request
2. 2” to 3 min - Dependent on ship speed and whether altering course
3. Every 6 minutes or on request

Question 5

5. List two things that are safety related messages are NOT for (2)

Answer 5

Distress
Personal messages

Question 6

6. State three advantages of AIS over Radar (3)

Answer 6

It can see round corners
It gives immediate indication of vessel altering course
Targets do not get lost in clutter

…and there are other advantages

Question 7

7. Why should the OOW not over rely on AIS information for collision avoidance? (3)

Answer 7

Information is provided from another vessel’s instruments, which we cannot check to be correct. CPA and TCPA is from a different source and could be incorrect. The ColRegs are based on visual and radar detection.

Question 8

8. What 3 modes of operation should AIS be able to work in? (3)

Answer 8

Autonomous and Continuous
Assigned
Polled

Question 9

List the elements of class A data

Answer 9

STATIC DATA:
* Call sign and name
* IMO number
* Length and beam
* Type of ship
* Location of GPS antenna

DYNAMIC DATA:
* Ship position
* Position time in UTC
* COG e SOG
* Heading
* Navigational Status
* Rate of turn

VOYAGE DATA
* Draught
* Hazardous cargo type
* Destination and ETA

Question 10

State the differences between AIS Class A and B

Answer 10

Clas B is nearly identical to class A but:
* Does not transmit IMO number
* Does not transmit destination and ETA
* Does not transmit navigational status
* Does not transmit navigationel status
* Does not transmit rate of turn
* Does not transmit draught
* receive, but does not transmit, safety and text messages