for development of SAR technology, and the Coast Guard is a promising research partner. As of the time of writing, its funding is modest, so synergies and advocacy from well-funded com-puter-science projects would likely be welcome.

In hindsight, the clearest lessons for the volunteer search team were that the ocean is enormous, and the Coast Guard has a sophisticated and effective maritime SAR program. The meeting in Berkeley opened with a briefing from Arthur Allen, an oceanographer at the Coast Guard Headquarters Office of Search and Rescue, which oversees all Coast Guard searches, with an area of responsibility covering most of the Pacific, half of the Atlantic, and half of the Arctic Oceans. Here, we review some of the main points Allen raised at the meeting.

SAR technology is needed only when people get into trouble. From a public-policy perspective, it is cheaper and more effective to invest in preventing people from getting into trouble than in ways of saving them later; further discussion of boating safety can be found at http://www.uscgboating. org. We cannot overemphasize the importance of safety and prevention in saving lives; the longer version of this article3 includes more on voluntary tracking technologies and possible extensions.

Even with excellent public safety, SAR efforts are needed to handle the steady stream of low-probability events triggered by people getting into trouble. When notification of trouble is quick, the planning and search phases become trivial, and the SAR activity can jump straight to rescue recovery. SAR is more difficult when notification is delayed, as it was with Gray. This leads to an iterative process of planning and search. Initial planning is intended to be quick, often consisting simply of the decision to deploy planes for a visual sweep of the area where a boat is expected to be. When an initial “alpha” search is not successful, the planning phase becomes more deliberate. The second, or “bravo,” search is planned via software using statistical methods to model probabilities of a boat’s location. The Coast Guard developed a software package for this process called SAROPS, 5 which treats

Gray was famous
for many things,
including his
determination
to work with
practitioners
to transform
the practical
challenges they
faced into scientific
questions that
could be formalized
and addressed
by the research
community.

the boat-location task as a probabi-listic planning problem it addresses with Bayesian machine-learning techniques. The software accounts for prior information about weather and ocean conditions and the properties of the missing vessel, as well as the negative information from the alpha search. It uses a Monte Carlo particle-filtering approach to infer a distribution of boat locations, making suggestions for optimal search patterns. SAROPS is an ongoing effort updated with models of various vessels in different states, including broken mast, rudder missing, and keel missing. The statistical training experiments to parameterize these models are expensive exercises that place vessels underway to track their movement. The Coast Guard continues to conduct these experiments on various parameters as funds and time permit. No equivalent software package or methodology is currently available for land-based SAR.

Allen shared the Coast Guard’s SAR statistics, 2003–2006, which are included in the longer version of this article. 3 They show that most cases occur close to shore, with many involving land-based vehicles going into the ocean. The opportunities for technologists to assist with maritime SAR are modest. In Allen’s U.S. statistics, fewer than 1,000 lives were confirmed lost in boating accidents each year, and only 200 to 300 deaths occur after the Coast Guard had been notified and thus might have been avoided through rescue. A further 600 people per year remain unaccounted for, and, while it is unknown how many of them remained alive post-notification, some fraction of them are believe to have committed suicide. Relative to other opportunities to save lives through technology, the margin for improvement in maritime SAR is relatively small. This reality frames the rest of our discussion, focusing on learning lessons from our experience that apply to SAR and hopefully other important settings as well.

 

Communication and Coordination As in many situations involving groups of people sharing a common goal, communication and coordination were major aspects of the volunteer search for Gray. Organizing these “back-office” tasks were ad hoc and