What happened?

One of the things that bugs me a bit about my GPS trainer, a Garmin Forerunner 305, is that it shows dramatic variations in pace, usually inexplicable. Check out this plot from today's run:

What's with all of those changes in pace? Am I really changing from a 12-minute pace to an 8-minute pace within the space of 50 meters? (Answer: Of course not. I probably went under a tree and lost the satellite signal briefly. But I wish there was some way the Garmin could correct for that.) And what's with that dramatic slowdown at Mile 5? I zoomed in on it on the map, and as you can see, it's in the middle of a residential area where two streets dead-end. There certainly wasn't any traffic there to speak of at 6:45 a.m.

Then I remembered: That's when a podcast I was listening to ended and I had to stop to cue up another one. Sometimes the GPS is telling the truth!

Today's run was otherwise uneventful, a 7.5-mile recovery run at a 10-minute pace. Tomorrow I've got a fast run planned with the DART group. I'm hoping to turn on the afterburners and see what I can do. Details of today's workout are below.