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gps-gb on ebay
It is totally misleading for ebay to state that GPS devices can use all 24 satellites that are orbiting the Earth. Fact is, half of them will be on the opposite side of the globe and out of sight. No more than 12 can ever be used. If your device shows more than 12 then there is software in your system to do this. Any receiver that purports to be better because it has, say 24 or 48, is simply marketing. At sea you only need 3 for a position. 4 or more is for a 3D position. You do not need a 3D position at sea as you are at sea level! The optimum marine gps receiver that is compatible with virtually any chartplotter is a Sirf Star 3 with 20 channels, as with ebay item number 150575857431. They are very simple to connect to your chart plotter, wiring details are sent in the package. Compatible with Raymarine, Lowrance, Garmin, Standard Horizon and many, many more that use an external receiver. You can also get this to work with plotters that have a failed internal gps receiver by simply using the settings in your plotter's menu if they have this option.