In reply to Cobra_Head:
> My old GPS used to do this under trees, especially if wet, it would lose the signal, and then seemed to take a while to pick it back up again, throwing the odd weird reading in there, hence the straight line.
My old one did that once in a while, I upgraded to a second-hand 630* about six months ago and it's been rock solid with never a blip before now, even when the same trees still had most of their leaves and were gopping wet.
*(£50! Bargain! God bless people with money to burn who have to have the latest model. )
I wouldn't have posted if it had lost signal for a bit and put in a straight line to wherever it picked up again though, this was a bit weirder than that hence the curiosity. It doesn't seem to have dropped out, the data points continue with a set of coordinates etc. every few seconds, but it's like it imposed a 'drift'. As if I was paddling a canoe instead of running and there was suddenly a strong current flowing North.
According to the track I suddenly went off the path at an angle, picked up the pace to about 1.5x what I was actually doing and ended up a couple of miles North of my actual finishing point. (Having done a bit over 19km instead of about 14km.)
Post edited at 10:09