International Loadline Zones
In the 1966 Load Lines convention, adopted by IMO, provisions are made determining the freeboard of ships by subdivision and damage stability calculations.
The regulations take into account the potential hazards present in different zones and different seasons. The current zones are displayed on a map below:-
When the scanner reports entering and leaving zones it does so by a series of short codes these are cross-referenced to the full zones names in the table below.
Code |
Zone Description |
---|---|
ASSTZ |
Arabian Sea Seasonal Tropical - Tropical: 1 Sep to 31 May, Summer: 1 Jun to 31 Aug |
BBSTZ |
Bay Of Bengal Seasonal Tropical - Tropical: 1 Dec to 30 Apr, Summer: 1 May to 31 Nov |
BLSSZ |
Black Sea Summer Seasonal - Summer for ships over 100m in length, Winter Seasonal Area for ships of 100m or less = Winter: 16 Dec to 15 Mar, Summer: 16 Mar to 15 Dec |
BSSZ |
Baltic Summer Seasonal - Summer for ships over 100m in length, Winter Seasonal Area for ships of 100m or less = Winter: 1 Nov to 31 Mar, Summer: 1 Apr to 31 Oct |
CSSTZ |
China Sea Seasonal Tropical - Tropical: 21 Jan to 30 Apr, Summer: 1 May to 20 Jan |
MSSZ |
Mediterranean Summer Seasonal - Summer for ships over 100m in length, Winter Seasonal Area for ships of 100m or less = Winter: 1 Dec to 28/29 Feb, Summer: 1 Mar to 30 Nov |
MSTZ |
Madagascar Seasonal Tropical Zone - Tropical: 1 Apr to 30 Nov, Summer: 1 Dec to 31 Mar |
NAGLZ |
North American Great Lakes Zone - Winter: 1 Nov to 31 Mar, Summer: 1 Apr to 30 Apr and 1 Oct to 31 Oct, Tropical: 1 May to 30 Sept |
NASSZ |
North Atlantic Summer Seasonal - Summer: For ships over 100m in length, Winter Seasonal for ships of 100m or less Winter: 1 Nov to 31 Mar, Summer: 1 Apr to 31 Oct |
NASTZ |
North Atlantic Seasonal Tropical - Tropical: 1 Nov to 15 Jul, Summer: 16 Jul to 31 Oct |
NAWSZ |
North Atlantic Winter Seasonal Zone - For ships over 100m in length = Winter: 16 Dec to 15 Feb, Summer: 16 Feb to 15 Dec For ships of 100m or less in length = Winter: 1 Nov to 31 Mar, Summer: 1 Apr to 31 Oct |
NAWSZI |
North Atlantic Winter Seasonal Zone I - Winter: 16 Oct to 15 Apr, Summer: 16 Apr to 15 Oct |
NAWSZII |
North Atlantic Winter Seasonal Zone II - Winter: 1 Nov to 31 Mar, Summer: 1 Apr to 31 Oct |
NEPSTZ |
North East Pacific Seasonal Tropical - Tropical: 1 Mar to 30 Jun, 1 Nov to 30 Nov Summer: 1 Jul to 31 Oct, 1 Dec to 28/29 Feb |
NPSTZ |
North Pacific Seasonal Tropical - Tropical: 1 Nov to 15 Jul, Summer: 16 Jul to 31 Oct |
NPSZ |
North Pacific Winter Seasonal Zone - Winter: 16 Oct to 15 Apr, Summer: 16 Apr to 15 Oct |
PSSZ |
Pacific Summer Seasonal - Summer for ships over 120m in length, Winter Seasonal Area for ships of 100m or less = Winter: 1 Dec to 28/29 Feb, Summer: 1 Mar to 30 Nov |
SIOSTZ |
Southern Indian Ocean Seasonal Tropical - Tropical: 1 May to 30 Nov, Summer: 1 Dec to 30 Apr |
SLRWSZ |
St. Lawrence River Winter Seasonal - Winter: 1 Nov to 31 Mar Summer: 1 Apr to 31 Oct |
SPSTZ |
South Pacific Seasonal Tropical - Tropical: 1 Apr to 30 Nov, Summer: 1 Dec to 31 Mar |
SUMMER |
Summer Zone |
SWSZ |
Southern Winter Seasonal Zone - Winter: 16 Apr to 15 Oct, Summer: 16 Oct to 15 Apr |
TROPICAL |
Tropical Zone |