On Sun, 29 Aug 2004 20:52:50 -0400, "JGK"
wrote:

Just curious as to the accuracy between the two.
The speedometer in my boat is a standard speedo nothing special, the
GPS is a Hummingbird Matrix 25 which I just got a week or two ago.
After a few outings I noticed that there is at times a considerable
difference
between the two and other times they seem spot on. Can't quite figure that
one out. Would a head current account for the boats speedometer to appear
at a higher MPH than the GPS?

Yes, the speedometer is relative speed to water, GPS is actual speed
over surface of earth.