what will work is this-program a bouy into your gps-then use the gps to lead you to it-as a waypoint-(remember loran?)-use thengps to check your basic compass and chart course and you will find the compass bearing on your boats compass and the heading the gps tell you to steer to get to the bouy are very similiar-(current or tide will account for the variation-then let the gps "tick off " the distance to the bouy and keep track of your position on the chart using "dead reckoning" i.e.-speed and time-and you will find yourself coming up on the bouys dead on every single time in limited visibilty-let the gps lead you from waypoint to waypoint-that's what it does-of ccourse your input of the lat lon of your waypoint has to be perfect 9some new charts have the major bouys allready done for you-but use it as a supplement to-not instead of your basic chart and compass course-Neil Gordon wrote: >>A GPS in neither a magnetic or gyro compass. I wouldn't use it at all as a compass.<<
The GPS lives in the past, while the compass lives in the present. I sailed from Boston to Provincetown and back last weekend... most of it in the fog so there were no visual marks to steer toward. Using the GPS heading as a "compass" causes oversteering every time... by the time the GPS says your heading and the bearing to the mark are the same, you've swung past your course. You get better at it after a while, though. Still, it's easier to steer by compasss and I found that doing so kept the GPS heading relatively steady.
As for comments relating to the position of the GPS in the boat... head out in heavier seas and position matters. As many have stated, the GPS doesn't know where the pointy end of the boat is. But... don't pretend that the movement of the boat at its center of gravity is the same as the movement of the boat at the bow or at the transom. We all know that's not true. If a boat is yawing through 10 degrees of arc, a GPS on the transom will move through that arc and the speed and heading shown will be effected. This was apparent on the P-town trip where my handheld and the boat's fixed GPS often differed as to speed and heading. Bearings to marks though, were right on, as each GPS was still doing its job of calculating position and the distance between the two units was only about 15 ft.
Regards, Neil
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Cape Dory 28 #167
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