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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.
Next page >
Sonar, Part 2 > Page 1, 2,
3, 4
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