Chart plotter speed wrong?

[l'escargot]

Had a run out in my RIB this afternoon. It's got a Garmin 451 chart plotter which normally behaves impeccably but today was giving speed readings in the region of double my actual speed. Shut it down and restarted it a couple of times, it was picking up plenty of satellites but was reading 9+ knots coming down the river when I was doing about 5 and was reading 45 knots when I was doing about 25. Position and everything else was spot on.

 

[timbartlett]

Had a run out in my RIB this afternoon. It's got a Garmin 451 chart plotter which normally behaves impeccably but today was giving speed readings in the region of double my actual speed. Shut it down and restarted it a couple of times, it was picking up plenty of satellites but was reading 9+ knots coming down the river when I was doing about 5 and was reading 45 knots when I was doing about 25. Position and everything else was spot on.

Sounds like it might have been switched to kilometres per hour. That would give readings 1.852x your speed in knots -- which sounds very close to what you are getting.

 

[l'escargot]

Sounds like it might have been switched to kilometres per hour. That would give readings 1.852x your speed in knots -- which sounds very close to what you are getting.

Thanks Tim, spot on - settings had somehow been changed from Nautical to Metric.