On what exactly? On the fact that your GPS watch will nearly never say the same distance that you just raced. Why is Humphrey so fired up, you ask? I’m not really, but I just answered an email from a very fast woman I coach who is insisting that she alter her marathon goal pace so that she can account for Boston being a long course.
We’ll live and die by our GPS watch, but not think twice that it’s not 100% accurate.
Now, I am not really that fired up. For one, we were really splitting hairs about the actual pace- it was a matter of 1-2 seconds either way. However, what worries me, is that she is accepting that her GPS is more accurate than the standardized certification process for race courses. That she is more willing to say that one of the biggest marathons in the world would be up to 0.25 miles long, rather than think that her GPS might just be a little bit off. What is really troublesome is that her thoughts are so common in the running world. We’ll live and die by our GPS watch, but not think twice that it’s not 100% accurate.
Here’s a couple articles I found doing a quick Google search:
With all of those articles, and I just picked a few, there’s no need for me to go into the measurement and the process. I can tell you- I’ve run though downtown Chicago, Boston, Manhattan, and other cities. Heck, the first mile of the Chicago Marathon goes down a hill and under ground for about 200-300 meters and my GPS loses signal there every single time! You have satellites trying to pick you up between massive skyscrapers and it’s bound to be off at least a couple feet. We all know that a couple feet here and there, over the course of 26.2 miles can add up!
So what do we do? Well, as much as it pains me, coach Mike Morgan offers up some advice that he uses for his marathons. I have adopted this for the last couple I have done, too.
- Turn the auto lap off! Take your splits manually. I really like this. That way you aren’t getting a buzzer where your GPS is trying to tell you where the mile mark is, rather than where the race is telling you where the mile marker is.
- I’m referring to Garmin here, because it’s what we have. I use two screens I can see. The first shows my lap pace and lap distance, I use that really more for a mental trick towards the end of the race- I can see how close I’m getting to the next mile and can convince myself to focus on maintaining my pace for that much longer. The second screen shows my average pace as one big number. Sometimes I’ll just flip to that so I can focus on keeping that average pace within my goal pace. Again, this is more of a mental trick than using it for measurement purposes.
Is doing this 100% accurate?
Well no, because I’m starting off with a device that’s not going to be perfect. What it helps with though is fighting that deflation feeling of hearing my watch lap buzz 50 feet before the mile marker sign and then 100 feet, then 150 feet… I know how deflating that can be to your mental state, which directly leads to slowing down and being frustrated. Nothing worse than having that feeling for no reason.
Alright, I’m getting off my soapbox. As always, thanks for reading!