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Piercing The Veil

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There are several reasons that one might want to know how to navigate in the fog. Fog is sometimes confined to a short stretch across a strait or channel. A half-hour trip in quarter-mile visibility might save a whole day waiting for fog to lift. It is less likely, but still possible to find yourself inadvertently surrounded by low clouds—where you’re only able to see the bow pulpit of your own ship. If you are prepared and the situation is taken seriously, traveling in reduced visibility is simple and safe. If you have had no prior experience with radar, there are courses offered by the U. S. Power Squadron and other organizations. If you have a basic understanding of radar, the next step is to gain confidence and then use radar to navigate through restricted visibility.

In most cases, commercial airplane pilots prepare to make entire flights ‘in the soup,’ meaning conditions of reduced or zero visibility. Having these conditions for the entire trip is rare but pilots are always ready just in case. Professional air crews have the necessary equipment to remain oriented in clouds and fog. They have rules and procedures they must follow. And they practice. If this pilot stuff does not make any difference to you, forget I mentioned it, except for one thing: the practice part.


If you eventually plan to cruise in reduced visibility, the time spent getting ready to go into the fog will help make the experience comfortable for you and your crew. Using the radar every day you are on the water is a good idea. The more radar-savvy a skipper and crew become, the more comfortable they will be in low visibility. Radar is very helpful when navigating in good visibility as well. It shows traffic ahead and behind your vessel. Electronic bearing lines show the potential for a collision early on.

If all charting and radar systems are operational, head out to sea in good weather and simulate low visibility. Plot a course and spend part of the trip navigating only with what you have available inside the boat. Make no reference to aids and landmarks outside. Someone on your crew needs to be on normal wheel watch, looking for traffic, logs, and crab pot floats.

If you have two screens, set the radar and chart plotter(s) in the same orientation (e.g. course up) and scale with the vessel in the center of both screens. This way you can keep track of traffic ahead and behind the vessel. If a course reversal becomes necessary you will be aware of possible headings to turn to. The shoreline and navigation aid “picture” should look the same on both the plotter and radar displays. With practice, you can superimpose the screens in your mind. Have the appropriate paper chart out and keep it oriented in case the computer/plotter decides to lock up (game over).

If there is a target on radar that does not show on the plotter, it is likely another boat. If a blip is sliding right down the electronic bearing line, a collision is inevitable. While in practice mode, peek out periodically to keep track of the real situation outside. When you see a target on the screen and can look out and know right where it is relative to your boat, you’ll gain confidence. The “same relative bearing” idea also works visually. If an object stays in the same spot on your window and just keeps getting bigger, it is time to do something to avoid a collision.

If there are ships or buoys that are not showing on the radar, this would be a good time to be sure the radar is tuned properly. Going over the fine points of radar use is for another day, but it is important to know the radar will show targets. Auto-tune and manual tuning procedures are discussed in your radar manual. I set the gain on our radar to show just a little “noise” so I know the set is working. If the screen is showing no targets, it means one of two things: Either you are completely alone, or the radar is not showing returns because it is not working properly.


When the fog rolls in on a day when you are motoring along, you should wade into the fog slowly. Have a definite plan in mind before the visibility goes down. Progress one step at a time. If a waypoint is the No. 2 buoy ahead, pass that mark, confirm its identity, and find the next mark on the chart and on radar. Track to the next mark, confirm your position and move on. Make a commitment to yourself and your crew that if you are uncertain of your present position, stop and figure it out. If that is not working, or anyone is too uncomfortable, go back to the last point where you were sure of your position and reassess the situation.

Cruising in thick fog is different. It is quiet. The wind is often calm or nearly so. There are usually fewer vessels out in low visibility. Keeping a listening watch for bells and horns is important. You are required to sound a horn every two minutes. Some VHF radios combined with loud hailers feature automatic fog signals. There will be more weather talk on the VHF with skippers trying to figure out how extensive the fog is and where other vessels may be. You should be very aware of the Vessel Traffic Service (VTS) in the area from previous experience and from depictions on nautical charts. It is important to coordinate crossing vessel traffic lanes with the controlling authority. Whether you plan to cross the traffic lanes or not, monitoring their VHF frequency will give you an idea if there are large ships in the area. If you wish to contact any vessel in the VTS lanes, be aware they will be on the VTS frequency and are not required to monitor channel 16.


Coast Guard Navigation Rules do not require radar on board in low visibility conditions but common sense does, in my opinion. That being said, skippers should know that rule 7 of the navigation regulations begins with the following:

(a) “Every vessel shall use all available means appropriate to the prevailing circumstances and conditions to determine if risk of collision exists. If there is any doubt such risk shall be deemed to exist.”

(b) “Proper use shall be made of radar equipment if fitted and operational, including long-range scanning to obtain early warning of risk of collision and radar plotting or equivalent systematic observation of detected objects.”

If you venture into fog (circumstances and conditions), you are required to make proper use of radar to obtain early warning of risk of collision.

The better prepared you are, the less stress you will experience and the more pleasure there is in pleasure boating. If you don’t have to worry about delays due to low visibility or getting surprised by unforeseen fog, you can enjoy time on the water even more.