Magic it's not, but cruisers who understand forward-looking sonar's limits are pleased with what it can do for them.
By Ben Ellison — July 2002
We have a problem: With the exception of some gloriously transparent tropical waters, we can't see where about half--a very important half--of our boat is going. Sure, we have charts that indicate dangers under the surface, and we can have a skeg that might protect our precious running gear if we do mess up, but what we really want is an underwater eye peering ahead of our bow. There is an electronic approximation of this called forward-looking sonar (FLS), and I set out recently to find out just how well it works.
First, some definitions are in order. We're not talking here about "side-scanning" or "searchlight" sonar. These beasts start at more than $10,000--"those are just the toy models," according to a Simrad representative--and their large mechanical transducers demand major installation. Though these machines can usually be made to focus their pings directly ahead for grounding avoidance, they are really meant for commercial fishfinding, even net management. Of more interest to most passagemakers are the FLS devices that use much simpler solid-state transducers and can be had for between $700 and $2,000.
Two companies, Interphase and EchoPilot, serve this market. Each has a particular scheme for scanning the water column vertically, from the bottom to the surface ahead, and delivering the resulting profile to an LCD display. It's important to note that this is meant to be a real-time snapshot, as opposed to the historical graph of bottom seen on a normal fishfinder, and it's much harder to generate. Unless you're a bat, it's really difficult to distinguish the incoming angles of multiple acoustic echoes!
Though Interphase and EchoPilot have both been offering their products for years, the percentage of boats they've equipped remains small. And I could find very little substantive writing about FLS in the boating press. All of this made the technology even more intriguing. Can forward-looking technology help a passagemaker avoid a floating container in the open sea or an uncharted rock in an unfamiliar anchorage? Fortunately, I was able to contact a number of actual FLS users for answers.
This article originally appeared in the January 2003 issue of Power & Motoryacht magazine.