Naval Postgraduate School Ocean Acoustics Laboratory

Shiptrack monitoring using the Automatic Identification System (AIS)

NPS established the AIS receiver network in 2008 to monitor vessel traffic along the central California coast.  Taking advantage of existing  Coastal Ocean Currents Monitoring Program (COCMP) sites along the California coast, AIS receive radios were added to expand AIS monitoring beyond the initial NPS stations in Monterey and Point Sur.

Current receiving stations are located at:

• Monterey (NPS), (4/24/08)
• Point Sur (NPS), (4/24/08)
• Pescadero Point (courtesy Peter Björklund), (8/11/08)
• Bodega Marine Laboratory (courtesy UC Davis), (09/15/08)
• Port San Luis (courtesy CalPoly, San Luis Obispo), (09/17/08)

The goals of the NPS AIS monitoring is to collect and archive ship track information along the California Coastline and compare the vessel traffic noise levels to the underwater recordings, as well as investigate any trends to marine mammal vocalization in the presence (or absence) of vessel traffic.  With the failure of the Point Sur Ocean Acoustic Observatory cable NPS does not have the ability to track marine mammal movement along the central coast.  Further marine mammal studies are limited (avoidance patterns, impacts, etc.) without additional hydrophone systems.

 Since AIS broadcasts using VHF frequencies, the operating range (ie, detection range) is dependent on atmospheric conditions.  Maximum reception ranges have been observed to vary between 51 km  (on poor days) to over 1,000 km during ideal conditions.  This data can provide a unique opportunity for atmospheric modeling electromagnetic signals.

Maritime Mobile Service Identities (MMSI) codes (Maritime ID, by country).

AIS receivers were purchased under a research grant from the Office of Naval Research.