REEFS, & THE LIKE CRASH AVOIDANCE, DETECTION!!

[Simi 60]

Originally Posted by Paul L

I don't choose to increase my risks, that's one of the reasons I use a forward looking sonar in addition to my eyes and good piloting sense.

Hold on I thought you said if you didn't get the timing right, therefore you are now in less than ideal conditions, you will go in and anchor anyway?

[Paul L]

Originally Posted by Simi 60

Hold on I thought you said if you didn't get the timing right, therefore you are now in less than ideal conditions, you will go in and anchor anyway?

It's all tradeoffs. Every situation is different. I can think of places in say Fiji in the Yasawas where heading back out in failing light is just as dangerous as continuing in.
What do you do when it turns over cast for a week after you are 3/4 of the way through a tradewind passge? I use the tools I have available and make piloting calls as to risk. Good piloting is easy when the conditions are perfect.

[Snore]

Originally Posted by Paul L

I think you missed my point. What I am wondering about is what criteria or algorithm do they use to 'average' multiple datasets. In areas with drifting bars straight averaging or weighted averaging with newer a greater weight might produce very poor results. If I understood how they are dealing with this then I could better judge the usefulness or reliability of the charts in particular areas. Do you know if they have published any info on how they handle this?

Gotcha—- In theory they should be weighing the new data over the old. But I have not seen, nor do I suspect they want to share, what black arts are used to determine depths.

Sonarchart remains my “chart of last resort” and would be replaced by visual navigation, if water clarity allowed.

[lituya1617]

I sank my last sailboat on the southwest coast of Cuba by hitting an uncharted rock in the middle of the night. The coast of Cuba is much like many coasts, littered with wrecks, unlighted, uncharted, and abrupt. The best way to avoid grounding or collisions on a sailboat is to follow rules designed to protect the sailor. I have developed my own set of rules after the sinking. A little late, but well motivated! Chief among these rules is to simply go slow when you cannot see far enough ahead to avoid hitting something. Better yet, hove to and wait until you can see where you are going. You are, after all, on a sailboat - which fact says you are not in a hurry. If you must sail at night, mount powerful spot lights on the crosstree so you can see ahead. In sea conditions more than a gentle swell, it is very difficult to see low-lying things like logs and shipping containers - nearly impossible at night no matter the sea conditions. As the wind increases, so must your caution. Stay at least five miles from any known coast at night, 10 miles would be better. It is better to sail into port than swim in. BTW I had a modern chart plotter which helped not at all to keep me from hitting what was not on the chart.