(This post was updated at 11 a.m. on Sept. 27.)
There's been a number of stories lately about astonishing discoveries by law enforcement using side-scan sonar.
- Last week in Oklahoma, state troopers testing a newly acquired side-scan sonar found two cars containing several bodies at the bottom of a local lake. The vehicles, and their occupants, had been missing for decades.
- Days later, the fire chief in Charlotte, N.C., said a team of his men training on their sonar equipment had spotted an airplane 100 feet down in a lake. Divers were dispatched but found no bodies. The authorities turned over the tail number to the Federal Aviation Administration hoping it might help solve the mystery.
- And in January, a Canadian team testing its new side-scan sonar found two cars, one reported stolen, underwater near a sunken harbor wall in Lake Ontario.
What's going on? And if sonar is so effective, why hasn't it been used more often?
In the Oklahoma discovery, Highway Patrol trooper George Hoyle, who made the find, told WPTZ-TV that using the sonar, he could clearly see an image of the cars: "It puts off a very good image and very detailed. I knew for a fact they were cars and they were pretty close to one another," he said.
Such stories are becoming increasingly common because the technology is more affordable and easier to use. Those important factors have come at a time when federal stimulus and Homeland Security dollars have gone into the coffers of local police and sheriff departments, giving them the resources to invest in side-scan, says Chris Combs, a sales manager at JW Fishers Mfg. Inc.
"Back in the '80s, [side-scan sonar] was a tool primarily used by the military, but in the past 30 years or so, the price has come down to the point where nearly any police department could get their hands on one," he says.
The side-scan sonar works on basically the same principle as a recreational boat's depth sounder or fish finder, Combs explains, except that a torpedolike "towfish" is dragged behind a search vessel to allow a wider scan of the bottom of a body of water. Having the information can reduce a search pattern and the time divers need to spend in the water and greatly increase the chances of finding a body, a plane or a sunken car, he says.
Combs' company produces a baseline unit for about $20,000 and provides a day of training to learn how to operate it. Less sophisticated models, such as the ones manufactured by Humminbird (which also makes recreational depth sounders and fish finders) can be purchased for as little as a few thousand dollars, he says. Training on how to use one of JW Fishers' units takes just one day.
"Absolutely, local [law enforcement] departments are making a lot of interesting finds," he says.
A team in Minnesota found a safe at the bottom of a lake, and even shipwrecks, long forgotten, have been uncovered with the technology, he says.
The Associated Press wrote last year about a semi-retired couple from Idaho who own their own side-scan sonar unit and volunteer to help with rescue and recovery efforts.
In all, Gene and Sandy Ralston have helped retrieve the remains of 80 people since they acquired the equipment in 2000, when it was much more costly than it is today. They ask nothing in return.