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34 Third IMO GHG Study 2014
Figure 25: Chart showing the coverage of one of the LRIT data sets used in this study (2012)
The quality of the bottom-up model’s activity and fuel consumption calculations was also checked against
operators’ fuel consumption data, contained in noon reports and fuel audits (see Section 1.4). No equivalent
data were reportedly used in the Second IMO GHG Study 2009.
This study uses IHSF data to obtain the technical characteristics of individual ships. While IHSF data were
used in the Second IMO GHG Study 2009, this study includes data on the status of a ship (in service, etc.).
Ship status data are obtained on a quarterly basis, so that ships that are reportedly active for only part of the
year are considered appropriately.
Method
The method developed by the consortium to conduct this study uses a comparable structure to the
methodology of the Second IMO GHG Study 2009 for the collation of aggregate data on activity parameters,
engine load and emissions. However, it is underpinned by analysis carried out at each calculation stage
on a complete database of the global fleet (i.e. all calculations are performed at the level of the individual
ship with aggregation of results only used for presentation purposes). This approach avoids the potential for
asymmetry or data bias that might reduce fidelity and accuracy. This represents a substantial progression in
the technology and practice of activity-based inventory methods for international shipping.
1.2.3 Aggregation of ship types and sizes
The algorithms used for vessel aggregation, developed by the consortium, build on aggregation methodologies
for EEDI (taken from IMO MEPC.231(65), expanded for ship classes not included in EEDI) and divide vessels
further into bins based on cargo capacity or ship size. The aggregations use definitions aligned as closely as
possible with those used in the Second IMO GHG Study 2009. In some cases, however, this was not possible
because the taxonomy used in the earlier study was not reported explicitly and because it did not always align
with the EEDI categories. Aggregation uses IHSF Statcode3, Statcode5, and relevant capacity fields to group
similar ships. IHSF organizes vessels into four types of ship:
• cargo-carrying;
• non-merchant;
• non-seagoing merchant;
• work vessels.
Most international shipping is represented by cargo-carrying transport ships, which are the primary focus of this
study. However, the other classes are needed to compare the bottom-up estimate with the top-down estimate
where both international and domestic voyages by oceangoing ships may be represented. The consortium
subdivided cargo-carrying vessel types into 13 classes, the non-merchant ships and non-seagoing merchant