Third IMO Greenhouse Gas Study 2014

178 Third IMO GHG Study 2014
sfc = sfc e × f e eq. (3)
The assumptions for sfc e are described in detail in Section 2 and the associated Annex 6. f e is estimated from
manufacturers’ data, as described in Section 2.
Aggregation by ship type and size
As discussed in Section 1.2, the activity and fleet data merger matches the IHSF fleet data to the AIS data,
determining whether there is a match by ship and whether the activity data is of good or poor quality. Good
quality activity data is currently defined as having day coverage of 10% or greater, although this assumption
will be tested for its impact on quality and uncertainty in Sections 1.4 and 1.5. The matched data is filtered for
good quality, creating a per-ship profile. The values in the per-ship profile are averaged across ship type and
size bins to create an aggregate ship type profile.
Fleet estimate assembly
Further estimation is required for unmatched ships within both a ship type and size category. The aggregate
average ship type and size profile is used to estimate the speed and draught profile, and this is then deployed
with the ship’s technical specification to calculate fuel use and emissions. This assumes that the mean speed
and draught for the ship type and size bin is representative of all ships within that type and size bin. Once this
step is completed, the per-ship profile is merged with the backfilled ships and the same aggregation by ship
type and size bin category is performed, this time with the complete fleet of in-service ships. The effect of the
uncertainty in the operational profile of the unmatched ships on the total inventory emissions is considered
further in the uncertainty analysis.