问答题 As The Economist went to press, Steve Fossett, a famed and fearless aviator who went missing over the Nevada desert on September 3rd, had not been found. But it was not for want of trying. Mr. Fossett has been the subject of one of the most intensive civilian manhunts in history—and also, fittingly, one of the most technological. Besides the usual panoply of search-and-rescue aircraft deployed by America's Civil Air Patrol, which wound down its search on September 17th, a different sort of search effort is being conducted online, using satellite photographs.
These pictures of the search area are being provided by two firms that supply information to Google Earth: GeoEye and DigitalGlobe. The search itself is being co-ordinated by a corner of the Amazon empire called Mechanical Turk. This is an online job market which farms out tasks that humans are good at, but for which software is poorly equipped, like labeling images and transcribing speech. For the Fossett hunt, volunteers comb through the images and flag any that include what might be a plane or its wreckage.
Among those who keep track of slightly less high-profile missing-person cases, the story will be strikingly familiar. In January Jim Gray, one of Microsoft's programming gurus, disappeared while sailing near San Fransisco Bay. Mr. Gray was as big a celebrity among computer geeks as Mr. Fossett is among thrill-seekers, and the story played out in the same way. A friend at Amazon, Werner Vogels, got in touch with DigitalGlobe, and the firm provided thousands of images. Within four days, Mechanical Turk was hosting the images and more than 10,000 volunteers were sifting through them—though to no avail, as Mr. Gray was never found.
Mechanical Turk's director, Peter Cohen, says that now the search protocol has been established, conducting such "distributed" searches is much easier. The limiting factor is the satellite imagery—which obviously has to be up-to-date. At the moment, only three commercial satel-lites provide the kind of resolution that can help in efforts like the Fossett hunt. The firms that own them have governments as their main customers. This makes search-and-rescue imaging a secondary concern.
That looks set to change, though. DigitalGlobe launched its second satellite, WorldView-1, on September 18th, and will launch a third late next year. GeoEye will launch its second next spring. This machine should set a new record for commercial satellite resolution: just 41cm (though that will still not be quite good enough to spot people as well as planes). In total, these launches will double the amount of satellite time that can be dedicated to requests for instant pictures.
Cost, however, is less of a problem. Area such as the Nevada desert and San Francisco Bay are not strategic, so taking photographs of them does not displace paying customers—indeed, DigitalGlobe is not charging for the pictures being used in the Fossett hunt. With the extra capacity provided by the new satellites, the cost will drop even further. And Mr. Cohen is convinced that the internet will always come up with the few thousand volunteers needed to scour the resulting images. Far from being the invasion of privacy it was recently claimed to be, the technology behind Google Earth may in time grow to be a standard search-and-rescue tool.