Glossary — G

24 terms starting with G.

• Gangway
  A portable access ladder or bridge rigged over the ship's side to allow persons to embark and disembark safely.
• Garbage Management Plan
  MARPOL Annex V required document setting procedures for collection, segregation, storage, processing, and disposal of garbage.
• Garbage Record Book (GRB)
  A mandatory log recording all garbage disposal and incineration operations on board, required under MARPOL Annex V.
• Gassing Up
  Replacing inert gas in LNG/LPG cargo tanks with cargo vapour before cool-down, eliminating CO2 and water that would freeze at cryogenic temperatures.
• GENCON
  BIMCO general voyage charter party (1994 / 2022 revisions); industry-standard for dry-cargo voyage employment.
• General Average (GA)
  Maritime law principle: voluntary sacrifice or expense made for the common safety of vessel and cargo is shared proportionally by all interests.
• General Cargo Ship
  A multipurpose vessel with cargo holds, tween decks, and derricks or cranes, designed to carry a variety of break-bulk and unitised cargoes.
• Generator Set (genset)
  A diesel-electric power unit installed in a ship's hold or on deck to supply electrical power to reefer containers.
• Global Maritime Distress and Safety System (GMDSS)
  An internationally agreed set of safety procedures and communications equipment required on SOLAS ships for distress and safety.
• Global Positioning System (GPS)
  US satellite-based radionavigation system providing position, velocity, and time data worldwide to marine and other users.
• GMDSS (Global Maritime Distress and Safety System) (GMDSS)
  The integrated radio + satellite distress + safety-communication system mandated under SOLAS Chapter IV.
• GMDSS General Operator's Certificate (GOC)
  Highest GMDSS radio operator qualification; required for service in Sea Areas A2/A3/A4.
• GMDSS Restricted Operator's Certificate (ROC)
  GMDSS qualification limited to Sea Area A1 (VHF DSC range only).
• GMDSS Sea Area A1 (Area A1)
  An area within range of at least one VHF DSC coast station providing continuous alerting coverage, typically within 20–50 miles of shore.
• GMDSS Sea Area A2 (Area A2)
  An area beyond A1 but within MF DSC continuous coverage, typically up to 400 nautical miles from shore.
• GMDSS Sea Area A3 (Area A3)
  An area beyond A1 and A2 within coverage of an Inmarsat geostationary satellite, covering most ocean areas between latitudes 70°N and 70°S.
• GMDSS Sea Area A4 (Area A4)
  The polar sea areas beyond GMDSS Area A3, not covered by geostationary satellites, where HF radio is used for distress alerting.
• Gob Rope
  Restraining line led from the towing point on a tug to a deck winch, controlling the angle of the towline.
• Graving Dock
  A watertight basin into which a vessel is floated, then dewatered, allowing access to the entire underwater hull for inspection and repair.
• Graving Dock
  Permanent excavated dock with a gate; fills with water to receive the ship, then is pumped dry for hull work.
• Great Circle
  The shortest route between two points on a sphere, formed by the intersection of the sphere and a plane through its center.
• Growler
  Small piece of glacier ice (<1 m above water, ~5 m across) — particularly dangerous because it is hard to detect on radar.
• Gyrocompass
  A compass using a gyroscope to find geographic north, unaffected by magnetic fields; mandatory on most large vessels.
• GZ Curve (GZ)
  Plot of the righting arm (GZ) against angle of heel — the cornerstone of intact-stability assessment.