Electronics | Techniques & Best Practices


The Ultimate Anchor Watch

By Gaz Haring
Published: October/November 2013

With today's electronics, you can tell if your anchor starts dragging without leaving your bunk. But make sure you understand your system's limitations .

GPS-Based Anchor-Watch Options

Most GPS units, even handheld, include an easy-to-use anchor-watch feature. For directions, refer to your owner's manual. Smartphone anchoring applications have proliferated in recent years, and some of the offerings give a lot of bang for the buck. These are still GPS-based systems with all the limitations described above, and care needs to be taken when choosing both phone and app.

Phones with built-in GPS work best because they don't require communication with cellular towers to establish their position. Those without an internal GPS stop monitoring when cell reception is interrupted. The GPS function and screen take quite a bit of power so choose an app that monitors even when the phone sleeps, and keep it plugged in when it's "on watch." Phones have small antennas resulting in poor reception belowdecks. To work well, the phone may need to be kept far from your bunk in a place where it gets a good GPS and cell phone signal, making a loud alarm imperative.

Apps are rarely subjected to the rigorous testing done by marine equipment manufacturers to ensure the system works as advertised. App support is often difficult to find, and few companies offer recourse if you have problems. But these applications make a good backup to your marine systems, and offer extra protection when used with them.

If you already have a compatible phone, an app with a short messaging service (SMS) function will alert you to a problem when you're off your boat, as long as you and the boat are in range of a cell tower. Out of the hundreds of anchor-monitoring applications available, Table 1 compares a few that have unique features.

Table comparing anchor watch apps
Click image to enlarge.

Alternatives To GPS

For maximum safety, set additional alarms on devices that utilize technologies other than the GPS system. Almost every depth sounder has an alarm that can be set to warn of changes. This is of little use if the bottom maintains a constant depth to a hazard, but can be very helpful otherwise. Security zones can be set on many radars to warn if something crosses into them, including another boat in a crowded anchorage. Plotters that combine GPS, radar, and depth into a single alarm function greatly enhance security. High power consumption and false alarms are disadvantages of these systems, but some have the advantage of communication features that allow monitoring from afar.

Motion-sensing anchor-monitoring systems cost several thousand dollars and use a sensor attached to the anchor to measure its movement to the inch. If you decide to spend the money, choose a system that transmits the sensor information through sonar because equipment using cables running from the boat to the anchor tends to suffer tangles.

Anchor-monitoring systems can make the difference between ending up on the rocks and taking action in time to save the day. But they're all fallible. Using several in combination with common sense, plenty of scope, and smart anchoring techniques can greatly increase the safety of boat and crew while keeping you sleeping soundly in your bunk.End of story marker

Gaz and Liz Haring have cruised the ICW from Mexico to Maine aboard their power cat Pegasus, including a few jaunts out to the Bahamas.

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