MnrAq

162 Third IMO GHG Study 2014
There are 102 different sea regions, as displayed in Figure 2. In the instance where a sea region is not found
for any coordinate pair, a valid sea region (1-102) is searched from the nearby cells with a search radius of 0.2
degrees. If a valid region is still not found then the region indicator is set to have the value of 0.
ECA mapping
Certain areas of the world have special regulations that affect the maximum allowed fuel sulphur content. As
fuel switching can occur in these areas to comply with these regulations, it was important to capture when
ships were in the affected regions. While the northern European ECA can be identified as a combination of
discrete sea regions, the North American ECA (NA-ECA) is a more complex subset of the Atlantic Sea, the
Caribbean Sea and the Pacific. Using the geographical mapping of NA-ECA, EPA (2013), a custom polygon
was added in the sea region identifier system (see Figure 3).
Figure 3: NA-ECA polygons drawn with Google Earth 2014
Outputs from pre-processing of raw AIS data
Following the parsing of the raw AIS messages, static and dynamic messages were merged to result in a
“complete” activity report for that ship at that time stamp. As highlighted above, static messages and dynamic
messages are linked through the MMSI number, with all information in a static message being associated with
all the following dynamic messages until the next static message is received and so forth. This results in an
array of tuples (ordered list of elements) containing MMSI number, IMO number, time, speed, draught and
message source region.
The 2012 and 2007 combined AIS data sets are shown in Figure 4.