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correspondence

Strategies for navigating around coral probably goes without saying that navigating around coral in areas without perfect charts and without good sunlight is a risky proposition. Depending on the season, the

that risk? Here are a few examples of what we felt were good reasons to navigate with bad lighting: Unexpected squalls: We raise anchor in full sun and start out our navigation in

latitude and the direction you are traveling, the ideal time of day for visual navigation varies, but it is generally in the hours surrounding high noon. Coral heads and reefs are best seen when the sun is high and behind you, the sky is blue, and the water is clear and flat. All things being equal, we try to only move about in atolls in those conditions. However, we have spent a fair portion of the last two years navigating in atolls in the South Pacific and there are numerous times when we have moved our cruising boat in a coral strewn lagoon in less than ideal lighting. Why would we take

ideal lighting conditions. Midway through our transit, squalls roll in, the rain starts, and our visibility is reduced to almost nothing. Incoming weather: The wind is forecast to change and we are not protected from a direction. The anchorage will become unsafe by the next day and we want to move, but it is a cloudy, gray day and visibility is poor. Large atolls: The atoll is large enough that we cannot transit from one anchorage to another in the ideal lighting hours. Safe pass navigation times: The slack time at the pass we want to transit is such that in order to get to

Livia Gilstrap

To the editor: It

Above, an example of a coral strewn area in nonpolarized light. Right, the same view in polarized light shows the coral and shallow areas more effectively.

20 OCEAN NAVIGATOR MAY/JUNE 2014  

the pass for the slack we have to leave before or after the ideal lighting. When these situations arise, we assess the relative danger of our options. In an anchorage, we have to decide whether it is safer to stay or to move. When underway, we have to decide whether it is safer to continue or turn around in the worsening visibility. Depending on the situation, we have a number of strategies for navigating around coral in less than ideal conditions. First, there are the ways we keep an eye on the weather and the route while underway: Keep track of safe areas when weather approaches: We keep an eye on the clouds and squalls while underway. When a squall approaches, we locate a safe area available to us to wait while the visibility is reduced. While underway in Penrhyn atoll in the Cook Islands we could see that a giant squall with heavy rain was going to overtake us. We found a large reef-free area and made a circle before the rain came. We knew that as long as we stayed inside of that circle we would not crash into any reefs. Keep track of safe headings: If the area is relatively www.oceannavigator.com

Ocean Navigator #218  

May 2014 Ocean Navigator

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