Bridge Equipment: SOLAS V/19 Carriage Requirements

SOLAS V/19 at a glance

In short: Read OOW duties and the safe navigational watch first: this topic is the kit that watch relies on. SOLAS V/19 (“Carriage requirements for shipborne navigational systems and equipment”) lists what a ship must carry on the bridge. The list grows with gross tonnage: a basic set for all ships, then extra items at 150, 300, 500, 3,000, 10,000 and 50,000 GT.

The basics every officer must know

• The Master and OOW must be familiar with every piece of bridge equipment before they rely on it.
• Equipment must be maintained and tested regularly, and kept in working order.
• Type-approved navigation equipment carries the wheel mark: proof it meets the IMO performance standards that SOLAS calls for.
• In the UK, SOLAS V is law through the Merchant Shipping (Safety of Navigation) Regulations 2020; the MCA guidance is MGN 610 (M+F) Amendment 1.
• Yachts: pleasure vessels under 150 GT are outside V/19, except the radar reflector (V/19.2.1.7). From 150 GT a yacht is in, like any other ship (MGN 610 (M+F) Annex A).

The tonnage ladder (SOLAS V/19.2)

Each line adds to the lines above it.

• Radar carriage, ATA/ARPA and the IMO radar performance standards have their own topic: radar rules and performance standards.
• Other Chapter V regulations used in this topic: V/19-1 (LRIT), V/24 (heading and track control), V/26 (steering gear tests and drills).

Compasses and bearing devices

In short: Every ship carries a magnetic compass because it needs no power. From 150 GT a spare one; from 500 GT a gyro compass with repeaters. The OOW checks compass error before departure, once a watch and after every large alteration.

The magnetic compass

• Carriage: all ships. Ships of 150 GT and over (and all passenger ships) also carry a spare magnetic compass (SOLAS V/19.2.2.1).
• Where: usually on the monkey island above the bridge, on the centreline, as far as possible from magnetic interference. Its card is reflected down into the wheelhouse.
• A hand-held magnetic compass is also useful for quick bearings.
• Variation = the angle between magnetic north and true north. It depends on where you are, not on the ship.

Deviation and its correctors

• Flinders bar position: bridge aft → bar fitted forward of the compass; bridge forward → bar fitted aft.
• Deviation changes with the ship’s heading, because the ship’s iron sits in a different position relative to the Earth’s field on each heading.
• Retention error and Gaussian error: after a long time on one heading, the ship keeps some of that magnetism for a while, so deviation is temporarily wrong after a big course change.

Checking the compass

Daily condition checks:

1. Gimbals free to move.
2. Card floating freely.
3. No air bubble in the bowl.
4. Numbers clearly readable.
5. Optical (reflector) system working.
6. Light working.

When to check compass error: pre-departure, once a watch, and after every large alteration of course.

How to check it:

• Transit: compare the true bearing of a charted transit with the compass bearing as the marks come in line.
• Alongside (pre-departure), square to the dock: compare the heading with the charted direction of the quay.
• Charted known bearing of a mark.
• Sun azimuth or amplitude (below).

Compass error by the Sun’s amplitude

1. Take a compass (or gyro) bearing of the Sun at sunrise or sunset.
2. Find the Sun’s declination for the date in the daily pages of the Nautical Almanac.
3. Note your latitude.
4. Enter the amplitude table of Norie’s Nautical Tables (or a rising/setting azimuth table) to get the Sun’s true bearing.
5. Compare true and observed bearings: the difference is the compass (or gyro) error.

Gyro compass and bearing devices

• Gyro compass: required from 500 GT, with a heading repeater at the emergency steering position and bearing repeater(s) (SOLAS V/19.2.5). Gyro error is checked by the same methods as the magnetic compass.
• Pelorus: a sighting ring on a magnetic compass. It gives relative bearings to the ship’s head.
• Azimuth mirror (or circle): fitted on a gyro repeater.
  • Arrow up for a bearing of a heavenly body.
  • Arrow down for a terrestrial object.
  • Keep the prism horizontal (watch the bubble).

GNSS, speed logs and echo sounder

In short: All ships carry a GNSS receiver. From 300 GT an echo sounder and a speed and distance log (through the water); from 50,000 GT a log over the ground too. Know how each works and what makes it lie.

GNSS (GPS)

• Principle: each satellite sends a signal with its time and position. The receiver knows when it was sent, works out the travel time and so the range to that satellite.
• 3 satellites → 2D position; 4 satellites → 3D position.
• Datum: GPS uses WGS84, a model of the average shape of the Earth. Your chart must be on the same datum, or the plotted position is wrong.
• Errors: satellite clock; satellite orbit; ionosphere delay; troposphere delay; receiver noise (interference from anything transmitting near GPS frequencies); multipath (signal bounced off mountains or buildings).
• Jamming = intentional interference with the GPS signal.

GPS segments, DGPS and DOP

• Space segment: 24 satellites in 6 orbital planes, 4 per plane (plus spares) — the minimum for global coverage.
• Ground (control) segment: a Master Control Station at Schriever Space Force Base, Colorado (alternate at Vandenberg). Older descriptions give it 5 monitor stations near the equator; the official US GPS website now lists 16 monitoring sites worldwide. Their job: monitor and maintain the system.
• User segment: anyone with a GPS receiver.
• DGPS improves accuracy: a base station at a precisely known position compares the range it measures with the true range, works out the error and broadcasts the correction to users in the area.
  • GBAS = ground-based augmentation system; SBAS = satellite-based augmentation system.
• DOP (dilution of precision): how reliable the fix is, given the geometry (azimuth and elevation) of the satellites in view. We watch HDOP (horizontal). 2 = good, 6 = poor, 8 = very poor.

Speed logs

• Doppler in shallow water locks on the seabed and gives SOG; in deep water it measures off the water and gives STW. The display tells you which.
• Janus configuration: beams forward and aft (and to the sides), so it also shows sideways movement.
• A wrong log speed feeds wrong data into radar plotting and ARPA: know which speed (water or ground) your radar is using.

Echo sounder

• Same principle as radar: send a pulse, time the echo, depth = speed of sound × time ÷ 2.
• Errors: multiple echoes (in shallow water with too high a frequency, or over a very reflective seabed), aeration, noise, density and propagation errors.
• Set-up: 50 kHz for deep water (longer pulse, travels further); 200 kHz for shallow water (short pulse, more precise).
• Transducer: well forward, about a third of the length from the bow, close to the centreline, away from turbulence, electrical interference and other hull openings.

ECDIS

In short: ECDIS (Electronic Chart Display and Information System) may replace paper charts when it is type-approved and has an approved back-up. Its job is to contribute to safe navigation: it sounds alarms, makes chart and publication updating simple and reliable, and so cuts the OOW’s workload (MGN 285).

ECDIS, ECS and the back-up

• ECDIS is approved and can be the primary means of navigation. An ECS (electronic chart system, even on a mobile device) is not approved and cannot.
• ECDIS carriage under SOLAS V/19 was phased in from 1 July 2012 to 1 July 2018 by ship type and size; other ships may fit it voluntarily (MGN 610 (M+F) Annex G).
• A typical paperless bridge: two ECDIS units, two GNSS receivers, two power supplies plus a back-up supply. Inputs: heading (gyro), speed (log), depth (echo sounder), and approved charts. Other sensors are optional.
• The MCA accepts as back-up: a second ECDIS, a type-approved chart radar fed by a different GNSS, or a folio of paper charts. Each ECDIS needs a UPS of at least 45 s (MGN 610 (M+F) Annex G).
• ECDIS is the ship’s track “black box”: it records position, speed and heading every 1 minute for at least the last 12 hours.

Chart data: standards, raster and vector

• The IHO coordinates world charting policy with the IMO.
• S-52: how the chart looks on screen, the same on every ECDIS. S-57: the digital data format for exchange.
• S-57 is being replaced by S-101 (S-100 framework): voluntary from 1 Jan 2026, mandatory for new ECDIS installations from 1 Jan 2029. Existing ECDIS can keep using S-57.
• Official ENC names start with the code of the producing hydrographic office, e.g. GB203804.

• Position, bearing lines, AIS and ARPA targets can be overlaid on both.

Displays and safety settings

• Base display: planning only — depth contours, own ship, no buoyage.
• Standard display: the minimum for navigation — base plus drying lines, buoys, beacons, other aids and fixed structures.
• All: every feature.
• Safety contour: the depth contour, chosen by the mariner and set by ECDIS, that separates safe from unsafe water. Drawn extra wide; ECDIS alarms if the ship will cross it within a set time.
• Safety depth: soundings equal to or shoaler than this value show black, deeper ones grey.
• CATZOC (category of zone of confidence): A1 (best), A2, B, C, D = decreasing survey quality; U = unassessed.
• SCAMIN (scale minimum): the smallest scale at which an object still shows. Press the 1:1 key to return to the compilation scale.

Alarms, warnings and monitoring

The 5 ECDIS alarms (often asked):

1. Crossing the safety contour.
2. Deviation from route (cross-track error exceeded).
3. GPS (position) failure.
4. Approach to a critical point.
5. Different geodetic datum.

Others: non-ENC area, malfunction.

Warnings / indications (information, not alarms): information overscale; larger-scale ENC available; route planned across a safety contour; route planned across a specified area; system test failure.

• Route monitoring: use the ECDIS route scan and a visual check of the route; set cross-track limits, look-ahead and all alarms.
• Integrity monitoring: ECDIS and operator continuously check the quality of the chart and position data — chart errors, position accuracy, sensor failures, display reliability, safety settings, alarms.
• Radar overlay is the best cross-check of the GPS position: see radar maps and ECDIS overlay.

Pros and cons

• Advantages: position always displayed; better spatial awareness; displays at the conning position, nav station and look-out; overlays for situational awareness; quick route planning; automatic log recording.
• Disadvantages: false sense of security; GPS can be inaccurate; information overload; the screen can block your view and spoil night vision; over-reliance; possibly old survey data.

AIS, BNWAS and the other items

In short: AIS from 300 GT on international voyages; BNWAS from 150 GT (cargo) and on every passenger ship; plus signalling lamp, radar reflector, THD, LRIT and weather instruments.

AIS (Automatic Identification System)

• Carriage (SOLAS V/19.2.4): all ships of 300 GT and over on international voyages; cargo ships of 500 GT and over not on international voyages; all passenger ships, any size. Keep it on at all times unless security says otherwise.
• Works on VHF. Inputs: VHF antenna, GPS, log, gyro, rate of turn.

• Can also send short safety and security text messages.
• SOTDMA (self-organising time division multiple access): a Class A set reserves its future transmission slots in advance.
• MKD (minimum keyboard display): lets you enter data manually; at least 3 lines of alphanumeric characters; must have an alarm.
• AIS for collision avoidance? Not on its own: it depends on the other ship’s equipment and inputs. It adds situational awareness. AIS on the radar picture: target tracking and AIS association.

BNWAS (Bridge Navigational Watch Alarm System)

• Carriage: cargo ships of 150 GT and over, and passenger ships of any size (SOLAS V/19.2.2.3). It must be on whenever the ship is underway.
• Purpose: proves the OOW is awake and on the bridge. If the OOW does not reset it, it alarms on the bridge, then calls the Master or back-up officer.
• On older, non-type-approved systems the MCA wants the time to the second-stage alarm no longer than 12 min 30 s (MGN 610 (M+F) Annex F).

The rest of the list

• Daylight signalling lamp — 150 GT and over.
• Radar reflector — under 150 GT (the one V/19 item that also applies to small pleasure vessels).
• Transmitting heading device (THD) — 300 GT and over: sends heading to radar, ARPA, AIS and ECDIS.
• Speed and distance indicator — 300 GT and over (see speed logs).
• LRIT (long-range identification and tracking) — SOLAS V/19-1: the ship reports its position by satellite to its flag State.
• Weather equipment: barometer (see weather instruments), weather facsimile receiver, and on sailing vessels an anemometer and inclinometer.
• Sailing vessels under the small-vessel code (MGN 280) also carry storm sails.
• Radar — X-band from 300 GT, S-band from 3,000 GT: details in the radar topic.

Steering gear, autopilot and steering tests

In short: The main steering gear must swing the rudder from 35° to 30° on the other side in 28 s. Test the steering within 12 h before departure, drill emergency steering every 3 months, and go to hand steering whenever it gets busy or blind.

What the steering gear must do (SOLAS II-1/29)

• A main and an auxiliary (back-up) steering gear.
• Main: able to steer at maximum ahead service speed and put the rudder from 35° on one side to 35° on the other, at the deepest seagoing draught; and from 35° on either side to 30° on the other in not more than 28 s (SOLAS II-1/29.3).
• Auxiliary: from 15° on one side to 15° on the other in not more than 60 s, at half speed or 7 kn, whichever is greater (SOLAS II-1/29.4).

The short version “35° each side within 28 seconds” is a common shorthand. The rule is 35° to 30° on the other side in 28 s; 35° to 35° must be possible, with no time limit given.

Autopilot and hand steering

• Follow-up: the rudder follows the wheel and stays at the angle you set.
• Non-follow-up: a lever or joystick; the rudder moves only while you hold it over.
• Switch to hand steering in good time in restricted visibility, high traffic density and when manoeuvring is critical, with a qualified helmsman available at all times (MGN 315 (M), SOLAS V/24). Test the manual steering after long use of the autopilot and before entering waters that need special care (SOLAS V/24).
• On the bridge: autopilot on a quiet ocean passage, hand steering approaching a TSS in fog — see conduct in restricted visibility.

Tests and drills (SOLAS V/26)

Within 12 hours before departure, check and test (where fitted):

1. Main steering gear.
2. Auxiliary steering gear.
3. Remote steering control systems, including their power failure alarms.
4. Steering positions on the bridge.
5. Emergency power supply.
6. Rudder angle indicators against the actual rudder position.

The test includes:

1. Full movement of the rudder.
2. Visual inspection of the steering gear and linkage.
3. Communications between bridge and steering gear compartment.

• Emergency steering drill: at least once every 3 months, steering from the steering gear compartment with communications to the bridge.
• Change-over instructions with a block diagram are posted on the bridge and in the steering gear compartment.
• Record tests and drills in the official log book (MGN 610 (M+F)).

The sextant: the back-up that needs no power

In short: Not a V/19 item, but still on many bridges as the ultimate back-up. A sextant measures angles; it is called that because its arc is one-sixth of a circle.

Sextant errors

Adjustable errors — PSI (correct them in this order):

1. Perpendicularity: the index mirror must be perpendicular to the frame.
2. Side error: the horizon mirror is not perpendicular to the frame.
3. Index error: index and horizon mirrors not parallel when the sextant reads zero.

Non-adjustable errors (their sum = instrument error, on the certificate in the box):

• Collimation error: telescope not parallel to the frame (only an expert can adjust it).
• Graduation error.
• Centring error.
• Shade error.

Coastal fixes with a sextant

• Horizontal sextant angles: measure the angles between 3 charted objects (a compass can also do it), then plot with a station pointer. Gives a fix without radar.
• Vertical sextant angle (distance off):
  1. Take a compass bearing of the object.
  2. Find its charted height (lights: above MHWS).
  3. Allow for height of eye.
  4. Enter the distance by vertical sextant angle table in Norie’s Nautical Tables.
  5. Bearing + distance = fix.

Celestial navigation

• You need: accurate time, a sextant, the Nautical Almanac and sight reduction (air) tables.
• Meridian passage (noon sight) gives your latitude; a sun-run-sun (morning sight run up to the meridian passage) gives a running fix.
• Azimuth = true bearing of the body. Altitude = angle above the horizon. Zenith distance = 90° − altitude.