The attached PDF illustrates an interesting situation. As you can see from the timing of the screen
shot, bottom right, the incident had taken place some 30 minutes earlier. The track clearly shows that shortly after an accurate fix, GPS
plus a couple of bearings on land silhouettes, the ship, steering
, took off on a 60 degree lurch to port followed by a starboard turn of about 120 degrees before coming back on the original course.
It didn't happen!
was fine, the wind
too light to sail and we were doing around 6 knots through the water
with about 1 ½ knots of fair tide pushing us along. We had about 30 metres under the keel
and the bottom is smooth. I caught site of the plot about halfway through the turn to port, and raced about the ship, checking the autopilot compass
, the magnetic steering compass
and searching for any possible interference
. Autopilot and steering compass both confirmed 'no change of course' and I could find no obvious source of electronic interference
. I also closed down CPN, switched off the laptop
and rebooted. The plot restarted seamlessly and continued as shown.
As I said, the conditions were perfect but what if this had happened in dirty weather
with poor visibility in restricted conditions?
Can anyone throw any light on this?