Many of us have become used to depending 100-percent on our electronics for navigation, but as you trust that little magic box of intel to get you home, there are a few details you should remember.
You may know all the chartplotter navigation tips, have all the latest digital charts loaded up in that little box of black magic sitting in the helm, and have all the coolest new electronics aboard, but that doesn’t necessarily mean the bow’s pointed at the inlet even though you think it is. Naturally, the biggest electronic snafus occur when there’s a system failure—if the MFD goes down, we sure hope you have a handheld back-up GPS and a compass on board. But sometimes, some electronics can lead us astray even when they appear to be working – because all of them are not created equally.
You’re passing through a harbor surrounded by tall buildings when your autopilot suddenly goes haywire and the boat veers off course. Or maybe you’re cruising down a cut surrounded by mountains when the boat diverts onto an unpredicted path. Sounds far-fetched? Not at all, and these are just a couple of examples of how multipath error and shadowing can turn your otherwise dependable heading into a wrong turn.
Multipath is a phenomenon where satellite signals get bounced around by a physical object, like a large tower, building, or even a big ship. If the bounced signal then hits your satellite compass, it’s coming from the wrong direction and it can fool your electronics into thinking your course has changed when it really hasn’t. Naturally, the autopilot then steers to correct in a manner that’s incorrect. Shadowing, similarly, occurs when a large physical object like a mountain simply blocks the signals out.
Everyone should know about these potential snafus so they understand what’s happening with their systems and why, but how do you solve them? The first and fastest way is to eliminate those confusing signals from the mix, by taking a step backward in time and steering the old-fashioned way – with your hands and the wheel.The other measure you can take is upgrading your electronics to include a satellite compass that’s not so easily confused. The new Furuno SCX compasses, the SCX-20 and SCX-21, are designed to solve issues related to satellite signal obstructions. While most satellite compasses calculate heading using one baseline between two antennae, the SCX uses four – giving it a total of six baselines. That vastly increases accuracy (to within 1.0-degree headings and 0.02-knot speeds) and reliability, as well as boosting accuracy when it comes to pitch, roll, and heave.
Another way our electronics can pull the wool over our eyes: they can simply miss things. Yes, we’re talking about radar in this case. Anyone who’s been surprised to see a boat suddenly appears out of the fog despite a blank radar screen knows exactly what we’re talking about. Many small fiberglass boats are poor targets for old tech or low-power units. Today’s more modern solid-state transmission wave radars have vastly enhanced sensitivity and do a much better job at picking up poor targets, though they may also more easily clouded by things like heavy rain.
The solution? Upgrade to a modern unit that incorporates both high-power pulse-magnetron and low power transmission wave tech. Yeah, this will get expensive, but these units really do give you the best of both worlds.
Even your fishfinder may be lying to you more than you think. Have you ever stared at some awesome structure on the bottom, only to realize that you’re looking at the result of your boat’s motion? That apparent changes in depth are appearing thanks to a wave or waves — not an actual hump or ditch in the bottom? Of course, you have.
The simple solution here is situational awareness. As long as you understand what can happen, you’ll know to keep your eyes peeled for it. That said, eliminating such deception is another perk the Furuno SCX compasses can provide, when combined with an FCV-1150 or NavNet TZTouch system. The SCX can feed its enhanced pitch and roll data to the fishfinder, which then can take the boat’s motion into account when displaying the bottom. (Added bonus: this same ability also helps provide more accurate echo trails on the radar screen).
Tech is a great thing, and it’s completely changed the way we navigate our boats, monitor our surroundings, and find the fish. And yes, you can trust that tech. But trust and verify.