Navigating a boat is a constantly changing task requiring different approaches and techniques depending on the area you're navigating and the sea and weather conditions. Mostly we use the "set the autopilot on a heading and check it every 15 minutes" method and ignore the depth sounder until we get near the harbor, but that method hasn't worked well for us in the ICW.
Below you see a little corner where we ran aground the other day. The dotted magenta line indicates the ICW centerline, but its not always accurate. The blue indicates sufficient water and the green indicates a shoal. The black lines are our tracks through this area.
Below is how the bottom really looks, so the chart isn't exactly accurate, is it? That jog is where we ran aground.
Since the charts aren't exactly accurate, and the depths are so shallow, the ICW demands a more intense level of navigation: constantly at the helm, frequently checking the chart for the magenta line and the deepest water, and using the depth sounder to determine if it's getting shallower or deeper as you turn.
Unfortunately for us, we were struck by lightning in August 2015, the cockpit read-out for our depth sounder was fried. The one at the nav station still works, but it's 10' away and poorly lit. Consequently we've run aground twice this week.
We've made some changes to our navigation method. First, we set the chartplotter to display "heads up" so turning towards deeper water is more intuitive. Then we zoomed way in so the details are bigger. And lastly, we taped a flashlight to the stairs and aimed it at the depth sounder.
And guess what; using a depth sounder really helps! Recently we went through Hell Gate and the Mud River with no problems.
So now it's all beautiful sunsets and rum cocktails here aboard Thistle.
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