August 2006

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Radar: Eyes Through Dark And Fog

By Capt. Ann Kinner

The view from my office this morning is classic San Diego: light haze over the bay and around the skyline, Mexico’s mountains outlined in the distance, clear sky overhead. It would be a very pleasant day to be cruising along the coast. Visibility: miles!

If I were, in fact, prepping the boat to get out of the slip, one of the first instruments I would be checking would be my radar, and I’d have it turned on for the duration of the voyage, clear sky or not.

During the run, I’d be adjusting the range – half a mile inside the bay, maybe a mile and a half in the approach to Point Loma, maybe six miles if I were headed for Ensenada through the Coronados.

Anyone who’s spent much time on the water in Southern California has been in fog so thick visibility was down to maybe a boat length. Anyone who’s run a boat at night in San Diego Bay or near the Los Angeles harbor knows the confusion of lights along shore that mask lights on the water.

The challenge for many boaters is translating the radar image into meaningful information in the midst of all the fog and confusion. Let me suggest a good book.

The Good Book

The Radar Book, by Kevin Monahan, is a clear, relevant lesson on radar for just about anyone interested in the subject. After a very short introduction covering the history of the device, Monahan presents a wonderful extended sequence of images that immediately clarify and relate the blobs on the radar screen to the details on the chart, and the view from the bridge.

With a minimum of technical language, Chapter One takes the reader on a trip from Victoria Harbour around the southeast coast of Vancouver Island through Sidney Channel and into Port Sidney. Each step of the voyage is illustrated with a direct comparison of the radar image and the corresponding chart, from the point of view of the helmsman.

The captions cover what appears and why, from radar shadows, to sea clutter, to buoys and boats. Just reading these captions and studying this sequence will teach you enough about radar to make you comfortable interpreting what’s on your own screen.

Adjustments And Controls

Chapter Two gets into the various adjustments, and the oddly named tuning controls. Monahan offers a step-by-step sequence from turning the instrument on to getting the best possible – and most useful – image. He explains "gain" and "sea clutter."

He shows the use of range rings and "variable range marker" to find your position on a chart. Then Monahan provides an extensive lesson on the use of radar to avoid collision, which may be the ultimate best reason to use radar: perfect visibility!

Specific Situations

If you only read these two chapters, you’ll be ahead of the screen. If you read the rest of the book, you’ll truly understand why radar is at the beginning of my tool list.

Chapters Three and Four cover the technical parts — displays, scanners, frequencies, beam width, horizon, reflectors, all the hardware involved. Chapter Five offers an extended discussion on optimizing the display.

Chapter Six talks about interconnecting radar and navigation equipment, including computers. The balance of the book covers the use of radar in specific situations, from poor visibility to heavy seas, and, finally, the kinds of things that can go wrong and what to do about them.

On The Side

All through the book are side notes, comments that fall outside the immediate text but that further explain or illustrate some critical part of the total radar package. For example, why does a cargo ship make a good target, while the shoreline around Catalina makes a poor one?

Why does the width of the radar beam matter? Should you keep the old (still-working) radar or get a new one?

At the end are an appendix on technical specifications, a short glossary for quick reference, and a bibliography with a list of Internet resources for information specific to various radar manufacturers.

Beyond Informative

Beyond its information value, this book was an interesting book to read. I can recommend it for anyone who uses radar, would like to use radar, or is simply curious about the concept of seeing through the fog.

The Radar Book is available at is available at Seabreeze Books and Charts in San Diego ( — Arizonans welcome! — and at many other fine nautical stores.