Third IMO Greenhouse Gas Study 2014

Annex 3 199
Further examination of specific regions can be found in Figure 13, which shows the average volume of AIS
activity reports for a region reported by a very large crude carrier (VLCC). Note that it is not the volume of
reports that is important, but the change in the volume, as one would expect the volume of messages to vary
across regions. It is also important to note that while the regions at which ships call varies from year to year,
any bias is assumed to be removed through the sample size selection and the ship categories selected.
The reduction in the Persian Gulf and Singapore Strait regions following 2009 is due to the change in data set
from IHS to other terrestrial data sets. Notwithstanding this reduction, the coverage remains significant, but for
some coastal regions 2010 has the poorest coverage. However, this improves significantly in 2011. For ocean
regions, the coverage dramatically improves from 2010 onwards.
Figure 13: The average volume of AIS activity reports for a region reported by a ship
for up to 300 randomly selected VLCCs from 2007 to 2012
Figure 14 shows a similar plot but in this instance is focused on the largest bulk carrier category. It shows
a message that is consistent with Figure 13, with consistent coverage around China and highly improved
coverage in ocean areas over time.