An important function of a chartplotter aboard today’s cruising yacht is its sonar bottom-scanning system. In my July 2019 newsletter, “Traditional depth sounders,” I extolled the virtues of simplicity and readability in a classic sounder. It reads out a number and that’s it, which is fine if all you need to know is the depth for anchoring.
Anchoring, of course, can be tricky business. The biggest advantage we get from sonar bottom viewing aboard a sailboat is when we are searching for the best spot to drop the hook in a questionable lagoon with coral and rocks looming beneath the surface. Ground formations, kelp beds, steep ledges and sunken vessels can conspire to form an obstacle course for cruisers looking for a secure anchorage.
The option to view fish shoals through a multifunction GPS monitor offshore while underway is definitely a plus for those of us who enjoy catching the occasional tuna or dorado. At anchor, this capability really comes in handy. If we’re hungry and want to haul in something nice for the barbecue, the sonar lets us know when it’s time to drop a line in the water.
Garmin, Simrad and Raymarine, among other electronics manufacturers, offer powerful color displays of bottom terrain in reasonably priced packages. Rather than looking at all the options offered in their chartplotters, we’ll compare only their depth sensing and viewing functions.
The ECHOMAP Plus 63cv from Garmin offers an optional sonar system with traditional CHIRP sonar and “ClearVu” scanning sonar combined into a single transducer. CHIRP sonar allows you to focus more power on a particular area for precise measurement than traditional sonar, detecting submerged objects and terrain details accurately.
Garmin’s ClearVu technology allows you to see bottom structure and fish at depths up to 2,300 feet with its GT20 sounder — much deeper than my traditional Signet depth sounder, which only detects down to 200 feet. ClearVu allows you to see bottom structure with “nearly photographic” images of what lies beneath the hull. The built-in Quickdraw Contours mapping software enables you to create fishing maps with waypoints stored for future use.
The Simrad Cruise 7 chartplotter/fishfinder combo with its 83/200 transducer is designed specifically for offshore cruisers who want ease of operation while following a GPS-mapped route and studying bottom formations at the same time.
You can choose full-screen mapping or a split-screen view to follow bottom contour and fish shoals simultaneously. Simrad employs CHIRP sonar, offering views up to 70 degrees from top to bottom and left to right.
The Simrad Cruise chartplotter series is intended for use on smaller boats, and therefore does not offer all the bells and whistles of more expensive chartplotters. The Cruise models do not support NMEA 0183, NMEA 2000 or AIS, but these units are great if you are on a tight budget and do most of your cruising inshore.
Another leading competitor in small chartplotters is Raymarine’s Axiom series, featuring “RealVision” 3D sonar. The Axiom is a standout with its attractive multitouch, multifunction, 8-inch display screen, which makes the job of navigating and studying bottom contour much easier and more intuitive than with buttons or dials.
Raymarine’s new LightHouse 3 operating system and standard CHIRP sonar combine to make soundings highly accurate both offshore and at anchor. The unit permits accurate viewing at depths of up to 900 feet, which is more than enough for fishing while underway.
There are certainly more makes and models of chartplotters/sounders available on the market, with most of them offering small units for around $500. Whichever you choose, make sure the unit is designed for your kind of cruising, which should include interface capability with AIS and VHF radio. This way, you can fish, get to your next port and find the best anchoring spot easily and safely.
Circumnavigator-author Bill Morris is the author of The Captain’s Guide to Alternative Energy Afloat and is a frequent contributor to Ocean Navigator.