NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Gyro Error.
From: Bill B
Date: 2013 May 21, 15:16 -0400
From: Bill B
Date: 2013 May 21, 15:16 -0400
On 5/20/2013 4:23 PM, Frank Reed wrote: > Suppose you're puttering along in the fog at 2 knots, which is just > about 1 meter per second. Now suppose the random noise in the GPS fixes > is around 2 meters. Suppose you are sailing at 8 knots in 5 foot seas, and your GPS is polling every second (likely faster). Suppose you have a GPS antenna on top of the mast. As the boat rolls the GPS is seeing significant lateral motion in relation to the forward motion. I have found this to be true even with handhelds and chart plotters with internal antennas located in the cockpit. Even in swells with the compass steady and a visual object dead ahead, plus/minus 3° is the norm. Trying to calibrate compass deviation with a GPS is truly a fools game. (This fool discovered that experientially ;-) Bill B
