Surveys

Underwater operations 162100Z to 232100Z apr in area bound by 43-04.0N 134-27.6E, 43-04.0N 134-42.2E,…

Japan Sea · HYDROPAC 1146/21

What this record establishes

Archived notice · 2021-04-23 22:00Z

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 XIII 20/21 140908Z APR 21.. Issued 2021-04-14 09:21Z. 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
Japan Sea. 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 Japan Sea →

Activity windows · 1 in this warning

opens (UTC)closes (UTC)locallength
2021-04-16 21:00Z2021-04-23 21:00Z—168 h

Parsed from the warning text; outside these windows the area is normally not active, but the warning stays in force until cancelled.

issued
2021-04-14 09:21Z
status
Archived notice
self-cancels
2021-04-23 22:00Z
authority
NAVAREA XIII 20/21 140908Z APR 21.
NAVAREA
NAVAREA XIII · named as the source of this relay
sea
Japan Sea
position
42.871, 134.482
source
NGA MSI broadcast-warn JSON (archive, frozen 2024-05) · first seen 2026-08-17 13:38Z

Original warning text

SEA OF JAPAN.
RUSSIA.
DNC 24.
1. UNDERWATER OPERATIONS 162100Z TO 232100Z APR
   IN AREA BOUND BY
   43-04.0N 134-27.6E, 43-04.0N 134-42.2E,
   42-42.0N 134-42.2E, 42-42.0N 134-14.0E,
   42-57.0N 134-14.0E.
   WIDE BERTH REQUESTED.
2. CANCEL THIS MSG 232200Z 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.
Underwater operations
Divers or remotely operated vehicles are working below a vessel that cannot easily move out of the way.
Date-time group (DTG)
A compact UTC timestamp — day, hour and minute followed by Z — such as 201500Z for the 20th at 15:00 UTC.
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

19 within 180 nm since 2003 · 3 in the last 12 months · 0 listed in force now

03
05
10
15
20
25
26

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

J
F
M
A
M
J
J
A
S
O
N
D

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 2026-10-01 11:54Z; 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.