What it is
Navigational Warnings (MSI) is a layer on the maritime map that shows active warnings to mariners. MSI stands for Maritime Safety Information. These messages include Notices to Mariners (NtM): alerts about temporary hazards, works in progress, movement restrictions, and other circumstances you should know about when planning a passage.
Each warning is tied to an area on the map. Areas are grouped by NAVAREA coverage zones — large sea regions that the world's oceans are divided into for distributing this kind of information. This lets you see at a glance which part of your route has restrictions or hazards.
Why it helps
The layer helps you spot problem areas ahead of time and factor them into voyage preparation:
- locations of temporary works and obstructions;
- zones with movement restrictions;
- areas where hazards to shipping are reported.
It saves time: instead of gathering scattered messages by hand, active warnings are shown right on the map.
How to turn it on and read it
- Open the maritime map.
- In the layers panel, enable "Navigational Warnings (MSI)".
- Warning areas and NAVAREA zone boundaries will appear on the map.
- Click a warning to open its full text.
The text usually states the affected area, the substance of the warning, and, where available, a validity period. The zone boundaries help you tell which NAVAREA a message belongs to.
Limitations
Please keep these important points in mind:
- The layer is for reference only and is not intended for actual navigation or course plotting.
- Before making decisions, always cross-check with the official sources of navigational information that apply to your area.
- Coverage and completeness may vary by region; the absence of a warning on the map does not guarantee there are no restrictions or hazards.
- Always use current official charts and publications as your primary source for safe navigation.
The MSI layer is a convenient overview tool for planning, not a replacement for official navigational information.