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Old 04-12-2012, 02:50   #1
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GPS Anchor Plot

One of the best things I have installed is a GPS next to the bed. I can see at glance where we are and that the boat is not dragging.
The wind was moderately strong last night, but gradually changing direction from Sto NW.
People often wonder what we mean by the semi circle trace that is produced by a boat swinging at anchor and I thought this was good example that I would share.
Notice the great accuracy achieved by a satellite differential fix. This plot was over 12hrs and there is not a single point outside a few meter range in the E-W direction.
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Old 04-12-2012, 02:56   #2
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Re: GPS Anchor Plot

Nice pic. We have done the same, but the most reliable is a diving weight on a long lanyard tossed out of the hatch and a slip knot around my big toe. No batteries, and it gets you out of bed automatically...LOL
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Old 04-12-2012, 03:24   #3
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Re: GPS Anchor Plot

Quote:
Originally Posted by sy_gilana View Post
Nice pic. We have done the same, but the most reliable is a diving weight on a long lanyard tossed out of the hatch and a slip knot around my big toe. No batteries, and it gets you out of bed automatically...LOL
Tying the string to a metal pot that will fall on the floor is another old trick.

The trouble is when the wind swings, you get woken up, because you have moved even when the anchor is not dragging.
The plot shows we have moved 150m (500feet) as the wind has changed direction. Importantly the distance to the spot I dropped the anchor has not changed.
This can be seen on the plot and is also reflected in the anchor alarm not going off. The anchor alarm is still sensitive enough that it will go off if we drag more than 5-10m (15-30 feet)
Sometimes technology beats the old tricks
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Old 04-12-2012, 05:09   #4
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Re: GPS Anchor Plot

I don't have a display in my berth, but do leave the nav desk unit on wit the anchor alarm set. roblem is that it doesn't make enoug noise to wake me when it is blowing out and I'm in deep sleep. I read once of a way to add a addition alarm to it but haven't gotten to it yet.

But I also find that the chart plot at anchor tells you a lot about how well you set you nchor and how it preformed overall.
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