MnrAq

242 Third IMO GHG Study 2014
Figure 29: Estimation of the power law relating deadweight to resistance
for samples of different ship types
Summary of input uncertainties used in the per-hour uncertainty analysis
Table 18 – Summary table of uncertainty characterizations used
Hour when observed on AIS
Hour when not observed on AIS
Input parameter Mean
Standard
deviation
Mean
Standard
deviation
Operation Speed Mean at-sea speed 11% Mean at-sea speed 18%
Draught
Mean at-sea 10% of mean Mean at-sea 10% of mean
draught
draught
IHSF specification Installed power Known to exist, but not known in magnitude and so assumed to be deterministic
Reference (design)
speed
Other technical
and operational
assumptions
Fouling-added
resistance
Weather-added
resistance
SFOC
C f
n
Aux/boiler
Equally uncertain, regardless of whether observed or unobserved; assumed here
to be deterministic
Known to exist, but assumed to be deterministic in this calculation
Known to exist, but assumed to be deterministic in this calculation
Significant for smaller ships, but assumed to be deterministic for larger ships
Known to exist, but not known in magnitude and so assumed to be deterministic
Uncertainty in the aggregation of hourly emissions into annual emissions
For periods of time during the year that a ship is not observed on AIS, we extrapolate from the measured
activity data. This extrapolation introduces uncertainty, as this step requires that assumptions be made. The
uncertainty analysis will propagate uncertain inputs at the per-ship-hour stage of the model into the per-shipyear
stage of the model.
In addition to uncertainty in the speed, for times when the ship is not observed on AIS, there is also uncertainty
about whether the ship is at sea or in port. The reliability of the extrapolation algorithm for estimating the annual
days at sea at varying levels of AIS coverage reliability was examined in detail in Annex 3 (Activity estimates