Join Date: Oct 2002
Location: Andaman Sea
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Originally Posted by montenido
Thanks everybody for the great replies. My GPS is actually a multifunction display - Raymarine C80, not 60 (sorry, my mistake). The compass is made by Richie. All of the equipment is relatively modern and probably works as intended.
Good points made about the difference in a bearing on a compass and the COG on the GPS. I just thought that the bearing and heading should be close. I don't remember exactly, but I think they were 20+ degrees different.
The reason it came up is that I set a waypoint for my marina 25 miles away and made towards it using my chartplotter. Even though I tried to follow the most direct route shown, I ended up doing more of an arc than a straight line. This was with no wind or current, just motor sailing. Not a big deal, but I probably covered a few more miles than necessary.
Next week I am going to Catalina Island, a trip of about 60 NM. I thought I would plot a heading using my charts as well as using the chartplotter with waypoints. On a 60 mile trip I would rather not add any additional miles if I can help it.
Thanks again for the great input.
If your track described an arc then I would guess you put the bearing needle (or equivalent ) and kept it pointing at the bow of bow of the boat and a current indeed was present and you arced to the destination. Very common for pilots too. If your GPS also has a function to read lateral drift and you adjust course to zero (lateral drift) then your track will be a straight line.
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Last edited by jerryrlitton; 08-12-2010 at 06:58 AM.