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Victim Searches
The anguish of the next of kin following a drowning tragedy is made worse waiting for their loved-one to be recovered.
Underwater searches usually require specially trained and equipped divers to first search and then make a recovery. This task is hampered by extremely poor visibility conditions. Most often search and recovery activities are limited to daylight hours, further adding to the stress of the family. In cases where an exact location is unknown, the search may take days or weeks.
The Hennepin Water Patrol uses a Sea Scan® PC side scan sonar to
quickly search large areas of rivers, lakes and ponds. A three person team with
a boat speed of approximately 3 mph, can search the equivalent of 50 football
fields in one hour. Forewarned about potential hazards and obstructions diving
is safer and more efficient. Recovery times have been reduced from days to
hours.
The Hennepin Water Patrol deploys the side scan sonar eight to ten times per year for both body and evidence recoveries. In addition, the Water Patrol Side Scan Team has assisted agencies other counties including Carver, Anoka, Ramsey and Crow Wing, and in Wisconsin.
How Does Side Scan Sonar Work?
Underwater, light is quickly diffused and very ineffective. Even the brightest lights yield only a few feet of visibility. A good analogy is driving a car in heavy fog. Headlights are nearly useless, but sound travels well in the fog, and even better underwater. The best way to "see" underwater is with sound.
Side scan sonar is a carefully engineered sonar designed to look through the water sideways, from both sides of a towed unit, to scan the bottom and return images to the surface. A computer processes the data and trained operators interpret the data and determine if the returned data is the target.
What does a Sonar image look like? Click here for an example.