I have a really good odometer on my road bike, but it consistently gives me more miles than my GPS...and than the measured mileage of the road. Even fiddling around to get the magnet in the right place on the spoke just couldn't quite give me at that sweet spot to "hit" the counter for an accurate revolution.
I can use the odometer as an approximate total of miles, but for greater accuracy I use the wrist GPS.
The Motion-X GPS app for smart phones is excellent! It gives you distance, average speed, maximum speed, change in altitude (change in ascent & descent), shows your course over a map (or satellite map), and lets you include photos along the way. I use it for mapping xc courses (I event). It's also super helpful in finding out just how far you've hunted and where all you went
Last edited by FoxChaser; Oct. 18, 2012 at 10:54 PM.
I just tried Runkeeper - a free iphone app this weekend. We were scouting new driving trails by bicycle. Easy to change between kilometers and miles. I would recommend trying it. Keeps track of speed and distance and records the "workout".