So during a passage race
off shore this weekend we were in really bad haze for a while out of site of the shores which were only 5 miles away or so. We were becalmed although I knew we had about 1/2 knot
boat speed as we were making a tiny wake. The skipper
started turning the boat back and forth and with the tiny breaze we had eventually got us stuck in irons. He then started making noises about "the bloody" gps
being wrong and which way to go etc...
I finally went to look and the boat was headed 270 on the compass
, boat speed was 1.8 knots but the "lead line" projection of course was leading out at 90 degrees i.e. off the bow of the little icon which was also headed 90.
I started laughing at the skipper
which is not a good thing to do 5 miles off shore but then had to explain to him why the gps
was "all screwed up."
We were heading 270 mag, but the gps doesn't know heading. It only knows direction. It aligned the little boat icon on 90 @ 1.8 knots because that is where the boat was going in the 2+ knot current
He has a speed log but it is uncalibrated. It reads about 1 knot when we are doing 4+ gps speed. I have asked him a couple of times to go out and calibrate it and took the opportunity to remind him again why it is good to have boat speed available.