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Old 22 March 2008, 13:33   #21
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Yes that's when you have to wipe the cobwebs off the paper charts...............
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Old 22 March 2008, 13:50   #22
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RIBase
http://www.ribmagazine.com/site/inde...=182&Itemid=84
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Old 22 March 2008, 13:52   #23
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Spiders web navigation is where you use a fixed point on a chart, normally the easiest is to use a compass rose, nearest to the area that you are going to be operating in.

Draw lines from the centre of the compass rose at 10 degree intervals. Then using either a pair of dividers with a pencil attached to them or a compass, measure extending distances in half mile intervals from the centre of the compass rose. Looks a bit like this: NOTE: none of the bearings or distances are to scale, this is just to explain the concept.



This is only really useful if you can put the position of the compass rose into the GPS as a waypoint and then make the GPS goto it. You will then be given a bearing and a distance, with this you can then plot it onto the chart and instantly work out where you are. For example you could be where the red cross is and instantly work out where you are.

Hence called a spiders web as it looks a bit like one.
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Old 22 March 2008, 14:04   #24
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Waypoint Web

Waypoint (spiders) Web is great for high speed position fixing in a small open fast boat.

You can use any waypoint ( not necessarily centre of compass rose) and the goto on your GPS. All you need is the range and bearing from your GPS to plot a position using the range rings and 'bearing lines' (not sown on the great graphic)

The beauty of using the centre of compass rose and range rings is that all you need is a straight edge....ruler/book spine..anything straight, to lay off your bearing from the centre of the rose, using the rose itself, out to the range rings. Instant and fairly accurate position fix. Clearly, the tighter your range rings, the more accurate your position is likely to be. e.g. cross channel, range rings of 5 miles is probably ok for 90% of the journey. As you close the coast, you might want to use 1/4 mile range rings for greater accuracy.
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Old 22 March 2008, 16:21   #25
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Clever. Hadn't seen that before!

John
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Old 22 March 2008, 20:35   #26
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Just on this note the Lowrance Ifinder that will take nauticpath and navionics chart cards is available for 60 at the moment in various online stores. I have just ordered one as a spare GPS so that if my main unit fails will be able to take out my navionics card from the main plotter and it will work as a mini plotter in BW.
The one I ordered even has a MP3 player attached, got to be a serious bargain at the price........
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Old 22 March 2008, 21:09   #27
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Which model is it and will I just be able to take my Navionics Gold card out of my Raymarine and stuff it in???
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Old 22 March 2008, 21:15   #28
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Ifinder Music and map. It is compatible with Navionics gold which is why I have just ordered one.
If the main unit conks out I can just swop the chart around and have a mini plotter to get home.
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Old 23 March 2008, 00:22   #29
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But it takes different cards.............
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Old 23 March 2008, 07:56   #30
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The handheld according to both Navionics site and the websites selling them is compatible with Navionics Gold cards in SD format. These are the same as used in Lowrance plotters.
According to online sources the only card they will not use is platinum
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