Lap pace screwed up after turning around to run home

I've been having similar issues (with pace oscillating wildly). What sorted it out for me was to switch from 1 second GPS recording to smart recording.

May be worth a try?

I have pretty much given up on using these type of devices for truly accurate distance and pace. I had a Polar device for 3.5 years and gave up using the GPS because it was about 95% accurate, which isn't nearly good enough. I've had the Garmin 230 for 5 workouts since I bought it, and the accuracy is a bit better, but still only about 97-98% accurate. I've lived in the same area for 17 years and have measured my courses enough times to know where I am at on the various key points on my courses.

What was really frustrating today was on an out and back the 2nd segment read 1.20 on the way out (which is spot on, and got me encouraged) and then was 1.11 on the way back. We have a lot of trees for sure, but it reminded me why I've never embraced GPS for running. The Garmin person today told me this was normal, but suggested I try the GLONASS option so I'm going to see how that goes.

Assuming you have a bike with a cateye or similar device, and have had it set up properly, just measure your courses several times and just use that information. I completely get it that it is deflating to be running say a comfortable 7:45 pace and have the Garmin tell you something 10-20 seconds slower.

My usual long run is 5 miles up a river trail, cross a bridge, and 5 miles home on the other bank of the river. When I cross the bridge at the halfway point, the pace calculation gets really inaccurate. For example, it thinks my pace drops from 9:30/mile to 15:00/mile.

Unfortunately this screws up the lap pace for the rest of the mile. I also have a pace range set for my custom workout, and it's really demoralizing to be told I'm running too slowly every 10 seconds for the next mile.

I don't know if the problem is that I'm changing direction (basically a 90 degree turn), or whether it's something specific about the bridge that interferes with the signal. Any pointers for resolving this problem? It's like the watch doesn't know that I've changed direction.

It's not a covered bridge, but has a lot of metal beams. The part that puzzles me is that the GPS tracked location doesn't seem to show any excessive inaccuracy. It's not like it thinks I'm continuing to run straight when in reality I've turned. Somehow it's tracking my position well enough, but not my speed.