Side-imaging sonar technology may help land big one

EUFAULA, Ala. -- Side-imaging sonar, technology used to locate the wreckage of the Titanic deep in the North Atlantic, is now available to anglers who just want to find a good fishing hole.

Such systems have been used for years in naval warfare, scientific research and underwater mapping, but until recently they were far too costly and cumbersome for the average fisherman.

That has changed with the recent introduction of new "fishing systems" offered by Humminbird, a leading manufacturer of electronic fish finders based in Eufala.

The company hopes the new $2,000 side-imaging sonar systems will become as essential to serious anglers as the tackle box, fishing pole and can of worms. It also predicts the systems will be a hit among divers looking for sunken ships, recovery teams searching for drowning victims, underwater archeologists and anyone else who needs a view of the depths.

"It is cutting edge," said Gary Caputi, editor of Saltwater Sportsman Magazine. "Nobody else has done anything like this."

Fish-finding technology has improved only incrementally since the mid-1980s, when sonar fish finders with liquid crystal displays were introduced, said Mark Gibson, Humminbird's global products manager.

Sonar detects underwater objects by bouncing sound waves off them and analyzing the results.

Traditional fish finders project sound waves directly below the boat and produce two-dimensional images on a display that shows the contour of the water's bottom, the depth and blips representing fish or other objects in the water.

Hummingbird's systems not only beam down, they also send sound waves to the side at a 30-degree angle. Their signals are fed into a microprocessor that produces three-dimensional images of objects up to 100 feet below the boat and 240 feet to either side. The images appear on a display similar to those found on laptop computers.

The systems also can be linked to global-positioning navigational gear so anglers can mark prime locations and return to them.

Structures are considered the most desirable spots because fish tend to congregate around them, either to hide from predators or to be predators.

"We were looking for something revolutionary," Gibson said. "We were thinking from the angler's perspective -- 'What would I want my fish finder to show me?' I'd want it to show me an image of what's exactly under water.

"Side imaging provides both the high-resolution images and works in all water, whether it's clear or muddy."

During a recent demonstration on Lake Eufaula, Gibson and Dave Betts, Humminbird's research and development manager, cruised slowly across the 45,181-acre lake as detailed images appeared on the display.

They saw a sunken barge and a pile of logs that had spilled out as the vessel went down.

Lake Eufaula, which stretches for 85 miles along the Alabama-Georgia boarder, was created in 1963 by damming the Chattahoochee River. The rising water covered buildings, trees, stumps and all other vestiges of human habitation. Gibson and Betts have found a submerged swimming pool, a bridge foundation, the remains of a hydroelectric plant and scads of stumps and trees. They can also see schools of fish or larger fish individually.

In military and commercial systems, which can cost more than $100,000, the transducers are either built into a ship's hull, or they are mounted in a torpedo-shaped "towfish" that is too heavy for the average angler to handle.

Humminbird's transducer unit, only six inches long and weighing only a few ounces, can be mounted to either the front or rear of a regular fishing boat.

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HOW SONAR HELPS ANGLERS

* The system provides life-like underwater images through the use of narrow beams of acoustic energy that fan out to the side and bottom of a boat.

* The acoustic signals are reflected from the bottom of a lake or stream and from objects in the water.

* Hard objects, such as steel, reflect more energy and produce lighter areas in the image that appears on a display.

* Softer objects, such as a muddy bottom, reflect less energy and show up as darker areas in the image.

* Areas behind objects are shielded from the acoustic energy and show up as dark shadows.

* Shadows give a three-dimensional quality to the image and are often the most important features used in interpreting the pictures.

SOURCE: Humminbird