Garmin Accuracy?

My Forerunner 305 has always been within .10 of a mile.

I would trust my Garmin before I trusted a RD

Yeah, no kidding! Even if you were on the outside of the turns and/or weaved across the street and/or the course was long, I would take the Garmin's distance to heart first.

I ran Flying Pig and my Garmin showed 26.49 miles, a 1.11% degree of error.



If we were talking the run segment of a triathlon I would agree. However, on a USATF-certified course like the Pig, I would trust the RD before I would trust my Garmin. The RD measures the course precisely and in a specific way per the USATF Course Measurement Procedures Manual. Often they hire trained Course Measurers to perform this task.

Now, as Daniel indicated, how you run the course that is laid out may make a difference.

Most marathons I've run have garmine'd out to about +1 mile.

Chances are very good that 1) the course was right on the money, and 2) you did run 27 miles. The RD will measure a course and chalk a line in the road, showing the measured course, presumably close to the shortest distance point-to-point. That's 26.2.

But we all know how marathons go...for the first 4 or 5 miles, you're weaving in-and-out of traffic, accumulating sideways mileage in addition to course-measured mileage.  If you don't run the shortest distance around corners and turns, more mileage. Ducking into porta-potties, veering to grab water at the aid station, dodging cups and gatorade in the street - more mileage. It adds up.

For Garmin marathon data fun, go to Motionbased Trail Network and enter in the location (ie Covington, Kenton, Kentucky). Then, do and advanced filter on Activity Name (ie contains Flying PIg). Now, you can see all the distances for Garmin users who have uploaded for that marathon.



Edited by camy 2009-05-16 10:41 AM