UKC

I went out for a 10 mile run today along a flattish trail surrounded but not buried by trees . For the second time in a week, at the same spot, about 3 miles in, my GPS watch had me going way off the trail (the same deviation both times), and achieving really rather impressive times. Apparently, today, I did a 6:30 mile, when the current pace indication at the time had me (busting a gut) to do 7:10 ish. The distance from there on was about 0.3 miles ahead of where it should have been, and I discover when I got home that I did a 58 s 400 m around about where it happened. All pish, sadly. I have run along this trail many, many, times without this happening.

Why does this happen, does anyone know, and what can I do about it?

The watch is a Garmin Forerunner 410.

In reply to mbh: yeah my 405 does this.. sporadically, normally in trees but not always.. anyway thank yourself lucky.. some guy the other day was clocked as doing the final 2 miles of a marathon at 30 mph (2 minute miles)... these garmins get confused..

In reply to IainRUK:

2 min miles is decent going, s'pose. I reckon I really was doing about 7:10 pace, which I wanted logged. I was trying 1 mile 7:10/8 min intervals. The weird thing is it has me wandering off up into the trees, making my 400 m split time one that even Seb would have struggled to beat. The exact same deviation both times this has happened, and I have run once along that route in between times with no mishap.

In reply to mbh: I get something wierd whenever I cross the Ben Franklin Bridge.. I ALWAYS get a sudden spike in altitude at two points on the bridge, 50m up and down again over 20 m or so.. yet I'm running on a fairly flat bridge..

In reply to mbh:

My Timex once recorded a total height deviation from 30-odd metres below the start point to 30-odd metres above it during the course of an evening run.

I was on a flat track at the time!

In reply to mbh:

That's nothing, on a couple of occasions I've run to North Africa and back several times, plus clocked 250,000 of ascent, all in my 45mins lunch break.