Surveys

Survey operations 30 mar thru 21 apr by M/V hesperides towing 1000 meter long cable in areas bound by: a.…

North Atlantic Ocean · HYDROLANT 858/21

What this record establishes

Archived notice · 2021-04-22 00:01Z

This notice comes from the historical archive. Its archived status does not establish when or how the reported situation ended.

Source and dates: NGA MSI broadcast-warn JSON (archive, frozen 2024-05) · NAVAREA II 133/21 291446Z MAR 21.. Issued 2021-03-29 15:10Z. First collected 2026-08-17 13:38Z; last seen in collection 2026-08-17 15:46Z. Collection dates record ingestion, not a new incident or a fresh field observation.
Location covered: North Atlantic Ocean. The map shows an area described by the warning; the listed coordinate is its representative center. Check the original wording for limits and qualifications.

Current notices and reporting history in the North Atlantic Ocean →

issued: 2021-03-29 15:10Z
status: Archived notice
authority: NAVAREA II 133/21 291446Z MAR 21.
NAVAREA: NAVAREA II · named as the source of this relay
sea: North Atlantic Ocean
position: 30.188, -15.764
vessel: M/V HESPERIDES · 31 messages
source: NGA MSI broadcast-warn JSON (archive, frozen 2024-05) · first seen 2026-08-17 13:38Z

Original warning text

EASTERN NORTH ATLANTIC.
CANARY ISLANDS.
DNC 01, DNC 08.
1. SURVEY OPERATIONS 30 MAR THRU 21 APR
   BY M/V HESPERIDES TOWING 1000 METER LONG CABLE
   IN AREAS BOUND BY:
   A. 30-52N 018-10W, 32-07N 013-35W,
      29-13N 013-35W, 29-00N 014-00W,
      29-00N 018-10W.
   B. 28-53N 017-43W, 28-59N 016-17W,
      28-38N 016-19W, 28-13N 017-21W.
   ONE MILE BERTH REQUESTED.
2. CANCEL THIS MSG 22 APR 21.

Reading this warning

DNC (Digital Nautical Chart): A reference to one of the regions of NGA's Digital Nautical Chart, used to tell the reader which charts a warning affects.
Survey operations: A research or survey vessel is mapping the seabed or water column, often while towing equipment.
Towed array / streamer: Equipment towed a long way behind a vessel — sonar, a hydrophone cable, a sampling sled — invisible at the surface.
Tow / towing: A vessel towing another vessel, a barge or a structure — slow, hard to manoeuvre, and with a long line between.
Area bound by: Introduces a list of positions that are the corners of an area — the polygon the warning applies to.
Position (degrees and minutes): How warnings write positions: degrees, a hyphen, then minutes, with N/S and E/W — 49-40.8N 003-43.8W.
Wide berth requested: Keep well clear — or, when a distance is given ("TWO MILE BERTH REQUESTED"), at least that far away.
CANCEL THIS MSG: The warning's own expiry: a line telling the reader when the message cancels itself.

All warning terms →

Collected reports in this area · survey operations

30 within 180 nm since 1999 · 0 in the last 12 months · 0 listed in force now

Counts include repeat notices about the same situation. NGA archive coverage ends 2024-05; live collection began 2026-08-17. The period between them is incomplete. An empty year is not evidence that no hazards occurred.

Month of issue in the collected archive

All available years combined. Uneven collection and repeat bulletins affect these counts; this chart does not measure the seasonality or probability of incidents.

Nearby notices listed in force · within 120 nm

No other collected notice is currently listed in force within this radius. This does not establish safe conditions.

Worldwide in the collected sources

55 survey operations listed in force · see all

Record snapshot 2026-10-02 03:26Z; source collection times vary.

Surveys

Hydrographic and scientific survey vessels, often towing long arrays. All current survey operations →

Not for navigation. This is a re-rendering of an official navigational warning for awareness; mariners must use official NAVAREA broadcasts and their national MSI service.