Marathon data: the Garmin Mystery

(still looking pretty good at mile 18)

So many numbers associated with a race, in this case the marathon.

From the race folks:
Distance: 26.1 miles
Chip time: 5:47:27
Clock time: 5:52:35
Pace: 13:15 min/mile

From the Garmin Training center:
Distance: 26.82 miles
Total time: 5:47:44 (a few sec longer since I didn't shut off the Garmin right at the finish)
Avg Pace: 12:57 min/mile

From MotionBased (an online service that works with my Garmin):
Distance: 27.4 miles
Total time: 5:47:44 Pace: 12:41 min/mile
Moving time: 5:42:46 Pace: 12:30 min/mile

So, which one of these is the right number? I think it is cool that the Garmin can keep track of when you aren't moving (I made two stops - one in the rest room and one to greet my family at mile 17 - so 5 minutes sounds about right).

Now I can understand a bit why the Garmin would measure a different distance than the official race distance. My understanding is that the race distance is the very shortest distance along the course so if you run wide or wander across the road it can make a difference over time. By the end of the race, the Garmin was registering mile splits 0.4 miles before I reached the marker on the course. But why would MotionBased indicate more than a half mile difference from the Garmin Training center? Inquiring minds want to know.

My mile splits per the signs on the course:

Mile 1: 12:26
Mile 2: 14:32 (bathroom break)
Mile 3 & 4: 25:32 (avg 12:46) (I never saw the 3 mile sign)
Mile 5: 12:31
Mile 6: 12:07
Mile 7: 12:26
Mile 8: 12:49
Mile 9: 12:26
Mile 10: 12:18
Mile 11: 12:23
Mile 12: 12:12
Mile 13: 12:08
Mile 14: 13:22 (conserving after giving up the 5:30 pace team)
Mile 15: 13:27
Mile 16: 13:31
Mile 17: 13:10
Mile 18: 14:55 (met with family)
Mile 19: 14:04
Mile 20: 14:23
Mile 21: 13:01
Mile 22: 15:27 (the wall!)
Mile 23: 14:20
Mile 24: 12:49 (almost missed a mile marker - hit lap button late making this short)
Mile 25: 15:28
Mile 26: 13:12 (running through Epcot felt good)
Finish: 2:33 (10:29 min/mile pace)

Later we will ponder the heart rate data....I am such a geek!