Guides

What navigational warnings are, how to read them, and what the archive can and cannot tell you. Each guide is written by seahazards and carries live numbers from the archive, recounted every night.

  1. How to read a navigational warning

    A line-by-line guide to the telegram style of NAVAREA, HYDROLANT and HYDROPAC warnings: headings, positions, date-time groups, instructions and cancellations.

  2. How navigational warnings reach ships: NAVAREAs, NAVTEX and satellites

    The World-Wide Navigational Warning Service explained: the 21 NAVAREAs and their coordinators, coastal warnings on NAVTEX, and the satellite broadcasts that reach ships at sea.

  3. Rocket launches and space debris: why areas of ocean close

    Why launch and re-entry warnings define large sea areas with time windows, where they cluster, and how to read a hazardous-operations warning.

  4. Lost containers, derelicts and other things adrift

    How shipping containers, abandoned vessels and debris end up in navigational warnings, why their positions age quickly, and how drift estimates are made.

  5. Sea mines and unexploded ordnance in navigational warnings

    Drifting mines, mine danger areas, munitions on the seabed and disposal operations: what these warnings report and how to read them carefully.

  6. Icebergs in the North Atlantic and the International Ice Patrol

    Why iceberg warnings rise every spring, what the limit of all known ice is, and why small pieces of ice are the harder hazard.

  7. Search-and-rescue broadcasts: distress, overdue and man overboard

    What a distress, overdue-vessel or man-overboard broadcast asks of ships, how rescue centres use them, and why seahazards publishes them only after a case is closed.

  8. GPS jamming and GNSS interference in navigational warnings

    How warnings report planned GPS testing and unplanned satellite-navigation interference, where it has been reported, and what the archive can and cannot show.

  9. Researching a maritime incident with the warning archive

    How to use seahazards to find what was in force at a place and time, along a route, near a port or under a ship's name — and what the archive cannot tell you.