disaster-response applications. For more on the organizational issues that arose in this more structured aspect of the search, see the longer version of this article. 3

Polytechture. The software-devel-opment-and-deployment process that emerged was based on groups of experts working independently. Some of the more sophisticated software depended on preexisting expertise and components (such as parallelized image-processing pipelines and sophisticated drift-modeling software). In contrast, some software was ginned up for the occasion, building on now-standard Web tools like wikis, scripting languages, and public geocoding interfaces; it is encouraging to see how much was enabled through these lightweight tools.

Redundancy was an important
theme in the process. Redundant ftp
sites ensured availability; redundant
drift modeling teams increased confi-
dence in predictions; and redundant
target qualification by experts provid-
ed both increased confidence and lim-
its on “responsibility bias.”
Perhaps the most interesting as-
pect of this loosely coupled software-
development process was the variety
of interfaces that emerged to stitch
together the independent compo-
nents: the cascaded Mechanical Turk
interface for hierarchical expertise in
image analysis; the ftp/email scheme
for data transfer and staging; the Web-
based “common operating picture”
for geolocation and coarse-grain task
tracking; the self-service “checkin/
checkout” interface for expert image
analysis; the decoupling of image file
access from image browsing software;
and the transactional workflow inter-
face for drift modeling. Variations in
these interfaces seemed to emerge
from both the tasks at hand and the
styles of the people involved.

The Web’s evolution over the past decade enabled this polytechtural design. Perhaps most remarkable were the interactions between public data and global communication. The manufacturer’s specifications for Tenacious were found on the Web, aerial images of Tenacious in its berth in San Francisco were found in publicly available sources, including Google Earth and Microsoft Virtual Earth, and a for-

The volunteer
search team’s
experience
reinforces the
need for technical
advances in
social computing.

mer owner of Tenacious discovered the Tenacious Search blog in the early days of the search and provided additional photos of Tenacious under sail. These details were helpful for parameteriz-ing drift models and providing “ template” pictures of what analysts should look for in their imagery. Despite its inefficiencies, the use of Mechanical Turk by volunteers to bootstrap the image-analysis process was remarkable, particularly in terms of having many people redundantly performing data analysis. Beyond the Turk pipeline, an interesting and important data-clean-ing anecdote occurred while building the search template for Tenacious. Initially, one of Gray’s relatives identified Tenacious in a Virtual Earth image by locating its slip in a San Francisco marina. In subsequent discussion, an analyst noticed that the boat in that image did not match Tenacious’s online specifications, and, following some reflection, the family member confirmed that Gray had swapped boat slips some years earlier and that the online image predated the swap. Few if any of these activities would have been possible 10 years before, not because of the march of technology per se but because of the enormous volume and variety of information now placed online and the growing subset of the population habituated to using it.

Networked search. It is worthwhile reflecting on the relative efficacy of the component-based polytechtural design approach, compared to more traditional and deliberate strategies. The amateur effort was forced to rely on loosely coupled resources and management, operating asynchronously at a distance. In contrast, the Coast Guard operates in a much more prepared and tightly coupled manner, performing nearly all search steps at once, in real time; once a planning phase maps out the maximum radius a boat can travel, trained officers fly planes in carefully plotted flight patterns over the relevant area, using real-time imaging equipment and their naked eyes to search for targets. In contrast, a network-centric approach to SAR might offer certain advantages in scaling and evolution, since it does not rely on tightly integrated and relatively scarce human and equipment resources. This suggests a hybrid