Like many runners, I have used GPS tools for mapping my runs to see how far and how fast I have gone. This has been an advantage for me when I have wanted to run a specific distance within a set time.

I started with a Nike+ watch that used GPS to track my routes and times. The watch would plug into my computer and save the information on the Nike+ Web site. I used that watch to track a particular distance — about a mile and a half out, so that I could do 5K runs by going out and back. When I did that, I got this map.

Note the distance is 3.1 miles. The problem is that my watch broke. More particularly, the connections inside the band failed. So, I sent it back to Nike, and since they had discontinued the watch, they very nicely gave me a voucher to replace it with another watch. (I welcome any suggestions on what would be a good replacement.)

In the meantime, I downloaded the RunKeeper app. at the suggestion of a friend of mine. I went out and ran the same route again. I wanted a 5K easy run after a bit of layoff thanks to a head cold.

This is what I got when I looked at their map.

This says I ran four miles! So, which one is correct?

First, I know that the sharp eyed among you will point out that there are more than two extra minutes on the Runkeeper time. I am not fast enough that I added an extra mile on in less than three minutes. Second, it also appears that my pace time is much faster, but again not so much faster as to make the difference. Most importantly, though, I covered the same ground, from the same start point to the same end point. I have landmarks at each end to measure it. I went to the same places.

I will need to clock the route on a car odometer next and see what happens. One way or another, though, something is off.

The main value of these tools for me is in laying out training routes. As I try to get faster and figure out better ways to run a 5K, it is not just about adding distance. Have a good sense of how fast I cover a particular distance is important to my goals, so finding something accurate is important.

Have you used one of these tools? What has been effective and accurate? Let me know. I will post the results of the odometer test soon.

In the meantime, here is a nice, succinct piece on how to train with a GPS device by pro athlete Lauren Fleshman.

Let me know if you use one, and how accurate you find it to be.