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JND320 Navigation Management > Section 7 - VDR & AIS > Flashcards

Section 7 - VDR & AIS Flashcards

1
Q

Limitations on AIS

A
  • The accuracy of AIS information received is only as good as the accuracy of the AIS information transmitted.
  • It would not be prudent for the OOW to assume that the information received is comparable in quality and accuracy to his own ship.
  • Not all ships will be fitted with AIS.
  • The equipment might be switched off.
  • the information given by the AIS may not be a complete picture of the situation.
  • AIS positions are derived from the target’s GNSS position.
  • Radar plots relies solely upon the data measured by the own-ship’s Radar and provides an accurate idea.
  • Incorrect info due to poorly configures or calibrated ship sensors.
  • Incorrect info displayed.
  • Elements of the dynamic info could be transmitted from sensors without accuracy.
  • Over reliance on AIS info.
  • The users remain responsible for all information entered into the system and the information added by the sensors.
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2
Q

AtoN

A

An AIS AtoN is a digital aid to navigation that is broadcast by an authorized service provider using the AIS Message 21 (Aids-to-navigation report) and is displayed on the ECDIS, radar or an Inegrated Navigation System. (MSC.1/Circ.1473).

  • A Physical / Real AIS AtoN is an AIS Message 21
    transmitted from an AtoN structure that physically exists. (99MID1XXX).
  • A Virtual AIS AtoN is transmitted as a Message 21for an AtoN that does not physically exist. (99MID6XXX). Should not be used for permanently marking an object instead should be included in ENCs
  • A Synthetic AIS AtonN is a physical aid to navigation structure, without an AIS transmitter, but for which
    AIS messages are broadcast from another (usually land-based) location.
    Monitored - A Monitored Synthetic AIS AtoN is
    transmitted from an AIS station that is located at a distance. The AtoN physically exists and there is a communication link between the AIS station and the AtoN which confirms the position and status of the AtoN. A Monitored Synthetic AIS AtoN ensures the integrity of the Message 21 and can be considered an alternative to the Real AIS AtoN.
    Predicted - A Predicted Synthetic AIS AtoN is transmitted as a Message 21 from an AIS station located at a distance.
  • The AtoN physically exists, but it is not equipped with a monitoring device to confirm its position and status and cannot ensure the integrity of the Message 21 (position and status), and therefore it is not recommended for use on a floating aid.
  • The use of a Predicted Synthetic AIS AtoN on a fixed aid is acceptable, as the position will not change, but the status of the AtoN is not verified.
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3
Q

Advantages to Virtual Aid to Navigation

A
  1. Where it is not possible, due to constraints, to establish a physical aid to navigation such as a buoy, beacon, or lighthouse.
  2. rapid deployment to immediately mark wrecks and prevent accidents by proactive notification.
  3. virtual aids to navigation are independent of weather conditions. They are always detected on the Electronic Chart Display and Information System (ECDIS) or radar overlay, providing timely information to mariners.
  4. they can be extremely helpful in areas where physical buoys are seasonally raised or relocated due to swell or ice or when a buoy is out of service or damaged due to a natural disaster.
  5. Easy installation and less maintenance. If conditions change, virtual aids to navigation are moved or removed.
  6. In addition, virtual aids to navigation provide good coverage despite rugged terrain or when approaching from inland waters. Ships can detect dangerous underwater hazards well before approaching them and know if they are on a collision course with a navigational hazard.
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4
Q

Disadvantages to Virtual Aid to Navigation

A
  • Not all ships can display AIS aid to navigation symbols.
  • Some ships with AIS equipment won’t read the virtual aids to navigation.
  • User might ignore virtual aids to navigation information.
  • Can be jammed or spoofed.
  • Info overload for the OOW.
  • Potential loss of signal.
  • AtoN using the wrong MMSI number.
  • Risk of navigation officers who are more familiar with traditional buoys and beacons missing this information because it is not visible in reality.
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5
Q
A
  • AIS Sleeping target
  • The triangle should be oriented by heading, or COG if heading missing.
  • The reported position should be located at centre and half the height of the triangle.
  • The symbol of the sleeping target should be smaller than that of the activated target.
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6
Q
A
  • Activated AIS Target
    Including Dangerous Target.
  • The COG/SOG vector should be displayed as a dashed line with short dashes with spaces approximately twice the line width. Optionally,
    time increments may be marked along the vector.

The heading should be displayed as a solid line thinner than speed vector line style, length twice of the length of the triangle symbol. Origin of the heading line is the apex of the triangle.

The turn should be indicated by a flag of fixed length added to the heading line.

A path predictor may be provided as curved vector.

For a “Dangerous AIS Target”, bold, red (on colour display) solid triangle with course and speed vector, flashing until acknowledged.

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7
Q
A

AIS Target – True Scale
Outline
The triangle should be oriented by heading, or COG if heading missing.
The reported position should be located at centre and half the height of the triangle. The symbol of the sleeping target should be smaller than that of the activated target.

Lost target
Triangle with bold solid cross. The triangle should be oriented per last known value. The cross should have a fixed orientation. The symbol should flash until acknowledged. The target should be displayed without vector, heading and rate of
turn indication.

AIS Search and Rescue Transmitter (AIS-SART)
A circle containing a cross drawn with solid lines.

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8
Q

AIS is defined as a system used for

A
  • A marine aid to navigation
  • A tool to assist in VTS operations
  • A tool to assist aids to navigation service providers
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9
Q

The main purpose of shipborne AIS

A
  • to be used in ship-to-ship mode for enhancing situational awareness in collision avoidance.
  • as a means for littoral States to obtain information about a ship and its cargo.
  • as a VTS tool.
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10
Q

What is AIS?

A
  1. AIS is a data exchange system (VHF data link)
  2. AIS equipped vessels and shore-based stations to send and received identification and other information.
  3. Help situation awareness
  4. Interfaced to RADARs and ECDIS
  5. AIS provide a source of target information.
  6. Fitted to physical aids to navigation (AtoN)
  7. AIS base station can broadcast a non-physical synthetic AIS Aton.
  8. No real(physical) AtoN exists.
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11
Q

AIS Component

A
  • 1 VHF transmitter.
  • 2 VHF receivers (AIS 1 and AIS 2).
  • 1 VHF DSC receiver (CH.70).
  • A standard marine electronic
    communications link and sensor systems.
  • Timing and positional information comes from a Global Navigation Satellite System (GNSS) receiver.
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12
Q

How AIS works

A
  1. An autonomous and continuous mode
  2. Use Time-division multiple access (TDMA) scheme to share a common VHF frequency.
  3. 2 dedicated frequencies
    a. AIS 1 : channel 87 B
    b. AIS 2 : Channel 88 B
  4. 27 identified AIS message types
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13
Q

Different means of transmission

A
  • AIS class A uses a self-organised approach (SOTDMA)
  • AIS class B units may use a carrier-sense approach (CSTDMA) or
    SOTDMA
  • AIS base stations use fixed slots (known as FATDMA)
  • AIS AtoN have an option to use FATDMA or a random access process called RATDMA, depending on the type of unit.
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14
Q

SOTDMA

A

Self-Organized Time Division Multiple Access, is the basic access method for mobile stations. Stations preannounce when they are going to transmit and plan their transmissions based on slot use information collected from other stations in order to prevent slot collisions.

  1. Is fully automatic and work without involvement of human intervention.
  2. It does not suffer from problem of mutual interference and resolves conflict, if any , on its own it is thus, ( Self Organizing)
  3. Accurate time signal from GPS are utilized for this purpose. Considering 2000 slots, spread over a time frame of one minute or 60 seconds, each slot will measure 30 milliseconds.
  4. These slot or time schedule take turn for several targets to transmit their data. (Time Division)
  5. Multiple slots (Multiple Access)
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15
Q

Classes of AIS

A

AIS Class A —
* Class A has been mandated by the IMO for ships of 300 gross
tonnage and upwards engaged on international voyages,
* cargo ships of 500 gross tonnage and upwards not engaged on
international voyages and all passenger ships (more than 12
passengers) irrespective of size, i.e. all SOLAS ships.
AIS Class B —
* Class B provides limited functionality and is intended for nonSOLAS vessels.
* It is not mandated by the IMO and has been developed for
vessels such as work and pleasure craft.

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16
Q

AIS operating modes

A
  1. Autonomous and continuous mode
  2. Assigned mode.
  3. Polled mode/Controlled.

Autonomous mode
- An autonomous and continuous mode for operation in all areas.
- AIS selects its own time schedule/slot defined its own reporting rate, which in turn depends on navigational status, speed course.
- No manual intervention on the ship is required.

Assign mode
- An assigned mode for operation in an area subject to a competent authority responsible for traffic monitoring such that the data transmission interval/or time slots may be set remotely by that authority.
- Remotely set transmission intervals and/or time slots.
- No manual intervention of the ship is required.
- In assign mode the mobile station does not change its reporting rate when changing course and speed.

Polled/Controlled mode
- This mode allow competent authority to request specific data directly form ship station
- The response is transmitted on the channel where the interrogation message was received.
- Operate in Polled mode does not conflict with the operation in other two modes.

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17
Q

Define Aids to Navigation Report

A
  • Type of AtoN
  • Name AtoN
  • Position AtoN
  • Position accuracy indicator
  • Type of position fixing device
  • On/ Off position status
  • Real and Virtual AtoN identification
  • Dimension of the AtoN and reference positions
  • Status of the AtoN systems
18
Q

Advantages of AIS

A
  • AIS can assist in tracking.
  • Immidiately apparent when change of heading and course.
  • Clutter, target swap or target loss do not affect AIS.
  • Identification of targets.
  • AIS can also be integrated with VDR and used to supplement investigations.
19
Q

Disadvantages of AIS

A
  • The target must be fitted with an AIS and turned on.
  • Relies on the target to provide accurate data.
  • AIS relies on all targets and own-ship for accurate positioning data (WGS84).
  • If GNSS fails, total failure of AIS.
20
Q

If there is only AIS return and no observed RADAR target

A
  • The target is obscured to the RADAR “line-of-sight”.
  • The RADAR is set-up in a manner that is not optimising target detection.
  • The target is obscured by sea or rain clutter.
  • Propagations conditions are such that AIS has a better range than the RADAR return
    from the target.
  • The RADAR is faulty.
21
Q

If there is a target indication only on RADAR and not on AIS

A
  • The target may not be fitted with AIS.
  • The targets AIS may be switched off or faulty.
  • Propagation conditions have a better RADAR range than AIS.
  • Own ship’s AIS is faulty.
22
Q

Annual Testing of AIS

A

SOLAS Chapter V, Regulation 18.9 states:
- shall be subjected to an annual test.
- The test shall be conducted by an approved surveyor or an
approved testing or servicing facility.
- The test shall verify the correct programming of the ship static information.
- A copy of the test report shall be retained on board.
up to 3 months before the due date of the passenger ship renewal survey or the
cargo ship safety equipment renewal survey; and

  1. up to 3 months before the due date of the passenger ship renewal survey or the cargo ship safety equipment renewal survey.

.2 3 months before or after the due date of the cargo ship safety equipment
periodical/annual survey.

23
Q

Pseudo AIS

A

VTS centres may send information about vessels which are not carrying AIS and which are tracked only by VTS radar, via the AIS to vessels equipped with AIS.

24
Q

AIS information sent by ships

A

Static
MMSI
Call sign and name
IMO No.
Length and Beam
Type of ship
Location of electronic position fixing system (EPFS) antenna

Dynamic
COG
SOG
Navigaitonal status ( should be changed as per situation).

Voyage
Draft
Hazardous cargo (DG, HS, MP)
Destination and ETA
Route plan (To be manually input at the discretion of the Master).

Safety-related
Free format short text messages would be manually entered, addressed either a speific addressee or broadcast to all ships and shore stations.

25
Q

General Principles of AIS

A
  • Take Special precaution to the primary purpose of AIS for collision avoidance.
  • even if a ship carries an AIS unit, the capability to portray or to display AIS AtoN information may be limited.
  • there is also a potential for conflict between charted AtoN and the portrayal of the same AtoN dynamically via AIS.
26
Q

Carraige requirements for VDR

A
27
Q

Purpose of the VDR

A

To maintain and store info in a secure and retrievable form concerning command and control of a ship over the period leading up to and following an incident.

The info should be available to the Admin and shipowner.

This info is used subsequently to identify the causes of the incident.

28
Q

VDR Performance Standards

A
  1. Recording of data continuous.
  2. Operate from ship’s main and emergency power.
  3. If power supply fail, continue to record bridge audio from dedicated reserves power source for 2 hours.
  4. 30 days/720 hours on the long-term recording medium and at least 48 hours on the fixed and float-free recording media.
  5. Data item which are older than this may be overwritten with new data.
29
Q

VDR data requirements and new aspects

A
  • Float-free recording medium should meet the requirements on an EPIRB.
  • A long term recording medium should keep data for 30 days.
  • Self test function
  • Storage of the data of the diving capsule extended to 48 hours.
  • Info should include the heel angle or roll motion.

Main changes in resolution MSC.333(90)

30
Q

Types of recording medium

A
  • Fixed recording medium, means a part of the final recording medium which is protected against fire, shock, penetration and a prolonged period on the ocean floor.
    • Maintain info for at least 2 years.
  • Float-free recording medium, means a part of the final recording medium which should float-free indicating position after a sinking.
    • Maintain info for at least 6 months.
    • Able to transmit location for 48 hours over a period of not less than 7 days.
    • New requirement for it to be constructed to minimize risk of damage during recovery opreations.
  • Long-term recording medium, means a permanently installed part of the Final Recording Medium.
31
Q

When must the performance test for VDR be carried out?

A

Annual testing

Can be done 3 months before or after of due date for Cargo Ship Safety Certificate and Safety Equipment Certificate.

Max. period between checks is 18 months for cargo vessels.

32
Q

Additional Data Types

A

ECDIS
- VDR is required to record ECDIS display as primary means of navigation, source and version of ECDIS.
- Screenshots at 15s interval.
- Should show exactly how the ECDIS was set up and used.

RADAR
- Revised performance required both X and S band radar screens to be recorded.

AIS
- Revised performance requires all AIS data to be recorded.

Electronic Logbook
- Logbook should be recorded.
- Inclinometer, if the ship is fitted, the ship’s rolling motion reconstructed when replaying the data.

33
Q

Revised Performance Standard for EPIRBs and VDRs

A

EPIRB
- Particularly for GNSS/AIS enabled EPIRBS.
- The beacon signal should include position fix and AIS locating signal.

VDRs
Due to the update in EPIRB’s performance, there is a need for the VDR’s float-free data to meet that latest performance.

34
Q

Proactive use of VDR

A
  • Essential equipment checked properly.
  • UKC adhered to.
  • Correct use of P.I. techniques.
  • Correct conduct of collision avoidance
  • Correct use of nav equip alarm.
  • Pilot integration with the team.
  • To replay VDR onboard for training purposes.
35
Q

Hex I.D.

A
  • A 15 hexadecimal character string, numbers 0 through 9 and letters A through F.
  • Uniquely identifies your 406MHz beacon and is encoded in the message your beacon transmits if activated.
  • When activated, satellites will detect the transmission and relay the alert to SAR services.
  • The Hex ID contains the country code and other identification features relative to the carrier which depends on the coding protocol used.
  • The Hex ID can identify the carrier using the radio call sign, a serial number, aircraft registration marking, etc.
  • The beacon’s Hex ID on a label affixed to the beacon or in the beacon documentation provided by the beacon manufacturer.
36
Q

Primary methods (AIS device access the link)

A
  1. Self-Organized (SOTDMA) is the basic method for mobile stations.
    Stations preannounce when they are going to transmit and plan their transmission based on slot use information collected from other stations in order to prevent slot collision.
  2. Random Access (RATDMA) is used by AIS station to access the link for unscheduled transmission.
37
Q

AIS Class A and B

A

AIS Class A
1. Mandated by the IMO for ship of 300 GT and upward engaged on international voyages.
2. Cargo ship of 500 GT and upward not engaged on international voyage and all passenger ship (more than 12 passengers) irrespective of size. All SOLAS ship.
AIS Class B
1. Provides limited functionality and is intended for non-SOLAS vessels.
2. It is not mandatory by the IMO and has been developed for vessel such as work and pleasure craft.

38
Q

AIS as surveillance tools

A
  1. Movement of vessels
  2. Monitor AIS transmissions
  3. Send information.
  4. Wide Area Network (WAN)
  5. Monitor the movement of hazardous cargo.
  6. Investigating an accident
  7. Search and rescue operation
  8. Pilot can monitor the position and movement.
39
Q

AIS as supplement to radar and ARPA information

A
  1. Shadow sector
  2. Bind sector
  3. Information instantly
  4. Target loss
  5. Target swop
  6. COLREG by all available means (situation awareness)
40
Q

Use of AIS in collision avoidance situation

A
  1. AIS does not replace but supports navigational systems such as radar target tracking and VTS.
  2. The use of AIS does not negate the responsibility of the OOW to comply at alltimese to COLREG.
  3. The use should not rely on AIS as the sole information system.
  4. Composition of the navigational watch.

JND320 Navigation Management (5 decks)

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