Third IMO Greenhouse Gas Study 2014

Inventories of CO2 emissions from international shipping 2007–2012 37
1.2.6 Sources and alignment/coverage of data sources
For the bottom-up method, calculations are performed on each individual ship’s technical and activity data.
For this, the consortium mainly used the IHSF database and AIS data sources and the majority of ships can
be identified in each of these for a given year. However, during the method development, the consortium has
recognized several ships for which a corresponding IHSF and activity data match does not occur (e.g. an IMO
number is not reported or the MMSI number does not match). Treatment of ships in such categories can be
summarized by the diagram presented in Figure 26, and is discussed below so that their contribution to global
CO 2 emissions estimates can be better understood.
Figure 26: Venn diagram describing the sets of ships observed in the two main data types used in the
bottom-up method (IHSF and AIS)
Type 1: IMO number is missing but MMSI number appears in both IHSF and activity data set
The SOLAS convention (chapter V) requires that all ships of >300 gt should install a class-A AIS transponder.
Furthermore, ships of 100 gt, therefore the consortium
retrieved both class-A and class-B data for this purpose.
Each AIS transponder has an individual MMSI code. MMSI transponder data from non-ships (e.g. fixed
structures, SAR aircraft) were excluded using message ID and the first three digits of the MMSI. Of the
remaining ships, for which no IMO numbers are reported in the activity data, the match was carried out on
MMSI number alone. However, this is not fully reliable because the record of MMSI numbers in the IHSF data
set is imperfect.
Type 2: MMSI appears in the activity data set only
The consortium recognized that some ships appeared in the activity data set only and did not match any ships
registered in the IHSF database. Three reasons could explain this mismatch:
1 erroneous or incomplete records in the IHSF database (e.g. incomplete list of MMSI numbers);
2 ships are operated only for domestic navigation purposes (in which case, the ships will be controlled
under each individual administration and do not need to be registered in IHSF);
3 the AIS equipment has reverted back to default “factory settings” of IMO/MMSI numbers. 1
1
See the Maritime and Coastguard Agency note MIN 298 (M+F): “AIS (Automatic Identification Systems) Operational Notification –
Safety of Navigation. ACR/Nauticast AIS”.