AIS Flashcards
Who is required to have an AIS class A? (3 factors)
Class A receivers required for all SOLAS vessels:
1. All vessels over 300GT on international voyages.
2. Cargo vessels over 500GT
3. All passenger vessels regardless of size
What is an AIS?
Automatic Identification System
AIS is an autonomous VHF transceiver navigation aid that transmits own vessel data and receives the same data transmitted from other vessels within range and transmits ship to shore. Range around 30-40nm. Works on two VHF channels (two frequencies) simplex (for ship to ship) and duplex (ship to shore).
What does AIS mean?
Automatic Identification System
What is dynamic data and how often does it transmit? (10 factors)
Every 2s - 3min
1. Navigational status
2. Rate of turn
3. S.O.G
4. Position accuracy
5. Position
6. C.O.G
7. True Heading & Bearing
8. Time (in UTC)
9. CPA
10. TCPA
Q
Where can you have an AIS overlay?
ECDIS, Radar, ARPA, IBS (Integrated bridge system)
What is the difference between Class A and Class B?
What is voyage data and how often does it transmit? (5 factors)
Every 6 minutes
1. Destination
2. ETA
3. Draught
4. Cargo type / class
5. P.O.B (persons onboard)
What is static data and how often does it transmit? (7 factors)
Every 6 minutes
1. IMO Ship Identity / MMSI
2. International Radio call sign
3. Name
4. Type of ship
5. Principal dimensions
6. Location of Positioning system
7. Type of positioning system
What are the AIS components?
Antennas
VHF Transmitter
2x Multichannel VHF receivers
Heading Input
Speed Input
Rate of Turn info
Position Input
MKD (Multikey display keyboard)
Why is navigational status a dynamic data?
Because if you for example go aground (and you change in AIS) that information need to be sent out faster and dynamic data has priority over voyage data
What modes of transmission (operation) are there? (3)
- Autonomous / Continuous mode
- Assigned mode
- Polling mode
Explain SOTDMA
In SOTDMA, the VHF channel is divided into time slots, and each AIS is assigned one or more time slots in which it is allowed to transmit data.
2250 time slots in minute, (4500 over two frequencies). This allows for three different modes of transmission.
Should AIS be used for collision avoidance?
It shouldn’t be the determining factor for collision avoidance due to reliance on other users input of data and sensors, however it is a great tool for overall situational awareness “all available means”. AIS has longer range than radar which means we can get an heads up of an upcoming target, it can also see around headlands. It can give information about target size and type which is beneficial.
How does AIS symbols look like?
What are the three AIS bouys and what would they look like on a chart?
-
Real / physical bouys
A physical navigation mark with an AIS transmitter affixed and data transmitted -
Synthetic bouys
A physical navigation mark without an AIS transmitter fitted instead relying on a shore based transmitter to project the information -
Virtual
No physical navigation mark and the data is transmitted by a shore based station
Elements of AIS Data
Difference between Class A & B (AIS)
AIS Consists of:
Dynamic Data transmission rates
Graphical display of an ACTIVATED AIS TARGET
AIS: A&B Comparison
AIS Inputs
AIS Info
Dynamic Data information:
Voyage Data Information
Static Data information
Class A & B Comparison
Modes of operation
AIS Symbols
AIS Symbols:
1. Real/Physical
2. Synthetic
3. Virtual
AIS Paper Chart symbols
AIS vs ARPA
