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Am just curious about that. Thanks.

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Am just curious about that. Thanks.

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That won't help, since the speed signal comes from the rear wheel.I'm thinking the 1%-2% error is caused by tire wear. I've got an appointment for a newtire in the morning. I'll check it and see what's up.front

My SpeedoHealer is set to minus 7.9% resulting in a dead-on speedometer, and the odometer then counts 5% to short. So it must read somewhat to long to start with. You do the math.

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Because of this, and hills and turns where distance traveled is the straight line between samples (typically taken at 1/second), and any internal inaccuracies of the device, GPS distance traveled records are at best 2 to 5% accurate even with WAAS.

Velocity calculations do not suffer from the accumulated positioning errors and are much more accurate. In North America GPS devices with a WAAS capability, which most have, are accurate to +/- 0.05 m/sec or 0.1 mph...

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That makes sense when you consider the GPS calculates distance as straight lines between points which understates how far you have gone in corners. The bike odo counts distance in tire revolutions times circumference of the tire when upright. But when you lean the bike over the circumference is smaller so you don't go as far as the odo thinks you did. That causes the odo to overstate distance in corners. The difference is small in any one corner but compounds for a day of riding lots of corners.

I calculate the error in my odo by comparing it to mile markers over a long distance on relatively straight roads. Using that method I'm consistently off about 1 mile in 100 miles.

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The GPS'

Running several random simulations I found the GPS "accuracy" to range from -0.3 to +3.9% with negative errors being rare, fewer than 1 in 30 simulations.

The average error in 100 simulations was +2.3%.

Why this occurs should be obvious from the plot, most positional errors cause the GPS' calculated distances traveled to be greater than the actual distance.

The vehicle GPS does not calculate based on straight lines (the GPS distances used for calculating advertised distances to stores and things use straight lines. It tries to send me to places over an hour away through the mountains when places within 20 minutes of me on the interstate are listed later). I calculates based on the road. I ride almost exclusively on very crooked mountain roads. The distance between Marion, VA and Tazewell, VA (Back of the Dragon) is 32 miles on Rt 16 and the GPS calculates and measures it that way. The distance between the towns is probably no more than 12-15 miles as the crow flies. I think the error between the odometer and the GPS is more to do with the size/wear/inflation of the tire, the inside of the curves vs the outside of the curves vs the center of the road, etc. I think the deviation of 1-2% is amazingly accurate.That makes sense when you consider the GPS calculates distance as straight lines between points which understates how far you have gone in corners. The bike odo counts distance in tire revolutions times circumference of the tire when upright. But when you lean the bike over the circumference is smaller so you don't go as far as the odo thinks you did. That causes the odo to overstate distance in corners. The difference is small in any one corner but compounds for a day of riding lots of corners.

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However when not navigating and just tracking trip info the device's calculate and accumulate distances between sample points--often with a lot of "fudge" added to some algorithms to reduced aggregate error.

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By straight lines between points I was talking about the lines between sample points on a curve not a straight line from beginning point to end point of a route. The GPS sees the curve as a series of connected straight lines not as a smooth arc. Each one of those straight lines is slightly shorter than the arc it represents. Individually those differences are minute but collectively over long periods they can be significant. Throw in the inherent problems with exact position of the sample points that Cliffy talks about and the equation becomes even more complicated.The vehicle GPS does not calculate based on straight lines (the GPS distances used for calculating advertised distances to stores and things use straight lines. It tries to send me to places over an hour away through the mountains when places within 20 minutes of me on the interstate are listed later). I calculates based on the road. I ride almost exclusively on very crooked mountain roads. The distance between Marion, VA and Tazewell, VA (Back of the Dragon) is 32 miles on Rt 16 and the GPS calculates and measures it that way. The distance between the towns is probably no more than 12-15 miles as the crow flies. I think the error between the odometer and the GPS is more to do with the size/wear/inflation of the tire, the inside of the curves vs the outside of the curves vs the center of the road, etc. I think the deviation of 1-2% is amazingly accurate.

By comparison the calculations the odo is doing are much more straight forward. It's just assumed circumference of the tire times revolutions. Complicating factors are tire brand, tire wear, tire inflation, and lean angle all of which can affect circumference.

Lane position in a corner would only be a factor if you are comparing the calculated distance to some predetermined measured distance like map distance or distance between mile markers. If you are comparing calculations of distance actually traveled between odo and gps they should both be affected the same way by lane position.

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As Suzuki doesn't want or need any lawsuits over warranties and odometer accuracy over the covered 12,000 miles that is what I would expect. The speedometer was off by +10%.

That was before I installed the SpeedoDRD of course...

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Buffalo as your up to 103k now that means you are in the TRUE 100k miles club.

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