SeaBird Exploration
SeaBird
Exploration provide
seismic services for the international gas and oil industry
and run a fleet of 8 vessels equipped with highly
sophisticated equipment.
SeaBird asked Sailsoft to develop software to dynamically
converting AIS messages of type 1 to NMEA RADAR $RATTM
sentences in order to feed the survey software aboard Hugin
Explorer.
This assignment was a real challenge because a number of
parameters in the TTM sentence have no direct counterpart in
the AIS message type 1 and have either to be calculated or
defaulted, including the calculation of CPA (Closest Point
of Approach) in time and distance units.
The Target Name
parameter in the TTM sentence is filled with the MMSI number
from the AIS message 1, since we decided not to interpret
message type 5. The program keeps a table for maximum 99
targets, because this is the maximum the NMEA $RATTM
sentence can bear.
Different threads are maintained for incoming and outgoing
messages. Message handling is complicated by the fact that
we have to deal with different speeds for incoming and
outgoing messages, 38400 and 4800 bps respectively.
The application is currently in operation aboard the Hugin
Explorer (pictured above).