gps

[David Butler]

How accurate is a GPS for miles per hour. My boat speedo says 45mph my Gps say's 48. Car speedo is 50mph Gps is 48gph. I know boat speedo are not that accurate but my car should be closer , i would think.

Dave

 

[Larry Harp]

I believe automotive speedometers are usually optimistic by 3 or 4 mph to as much as 6 or 7 mph at higher speeds. There are many variables from make to make, after market tire size changes, and tire pressure. I've always thought that GPS is dead on accurate.



Harpo

 

[Jim B]

GPS speeds can vary greatly depending on conditions. Gps always has a degree of error on your position and that can vary depending on cloud cover, mountians, building, trees etc. Because of that degree of error it can never 100%accuratly report your speed. Sure it can be close but it can be off by a few mph or more, and be can be off either faster or slower then you are really going. I have had mine tell my im going 5 mph when its sitting still on my desk.



To use a gps to measure speed you really need to sustain that speed over a good distance. If you just get up to speed and read it it can be way off because it can still think you are accelerating. I have had mine tell me my boat is doing over 70 just after i hit top end but if i hold it for a few miles it levels off to closer to my real speed(62). The GPS is closer then a speedo on a boat but far from perfect, but its close enough.

 

[Mark Gross]

Really how much faster or slower is 2 miles per hour..That seems about walking speed or a little bit slower.So when your in the car and the officer asks "Do you know how fast you were going" tell him 2mph less than what you were doing.If your talking about your boat and someone asks "How fast will it go give them the GPS reading.Just my pennies worth.lol