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October 03, 2012

Side-Imaging Sonar

Can side-viewing sonar help anglers see and catch more fish?

Dialed In

When Humminbird introduced ­recreational side‑scan technology to anglers in 2005, its first units used 262 and 455 kHz frequencies. Today’s units transmit at 455 and 800 kHz. The higher-frequency pulses give side-scan its imagelike qualities.

The 262 kHz frequency created even illumination, but 455 eventually won out for its image quality and crispness, Gibson says. The 800 kHz beam is very narrow, and while it can provide even greater detail, it can fail to read ­drop-offs and soft bottom.

“You might see more of a ­difference with 800 when using down-scan,” says Lucas Steward, Navico product manager. Down-scan gives anglers a detailed look at what’s directly beneath the boat; both Navico and Humminbird offer that view. “Most anglers are really learning more about their traditional sonar now that they have down‑scan.”

Steward says Navico’s brand-new StructureScan HD ($599 black box with skimmer transducer) boosts the ability of the 455 kHz signal, creating the same or better resolution than the previous 800 kHz. StructureScan HD, coupled with Lowrance’s new HDS Gen2 display ($549 to $2,449) with the StructureMap function, allows anglers to overlay side-scan imagery to build a map of a specific area.

The Low-Down

Most smaller boats use transom-mount transducers for side scanning, but through-hulls are available for larger boats. Currently, both companies offer a plastic through-hull transducer, and Navico says its HD bronze version ($359 to $1,999.95) will start shipping in early November.

Anglers who own boats with a sharp deadrise at the transom can opt to mount a pair of transducers; each shooting a signal to capture information on its side of the V.

For all-around-the-boat viewing, Humminbird recently introduced 360 Imaging, which adds forward imaging to side and down imaging — dialing in structure and fish up to 150 feet from the boat. The hardware consists of a deployable transducer that’s raised and lowered when needed.

Due out at press time, 360 Imaging costs $1,999. “This doesn’t replace side imaging,” Gibson says. “I can use side imaging to find stuff, but with 360, I can sit there just off a dock and fish that spot. I can see fish move while I’m casting.”

That’s what you might call “virtual scuba diving.” 

Trial Run


To better familiarize myself with side-scan and to discover what it really can do in muddy salt water — common conditions near my coastal Georgia home — I recently installed a Humminbird 998c SI Combo aboard my bay boat. I have a subsequent install scheduled with Lowrance to experience the HDS Gen2 with ­StructureScan HD.

Go to to view a video of the installations, along with future links to blogs and photos on how this technology works, as well as links to Humminbird and Navico videos on side-scan.