This morning I ran twice with one watch hooked up to a Stryd and set to Always use for Pace and Distance and another just on GPS. In both cases the Stryd came up with a longer distance. First up was a trail run that we've been running for years so we know it is close to 9km. Stryd returned 9.31 where my GPS Trail Run gave 8.99 and my wife's 945 8.97km. Next up was parkrun. For those who don't know, parkrun is always 5km. Our parkrun has been accurately measured using a calibrated wheel so we know it's 5.04km from the wheel. And every GPS run we've done has been 5km +/-20m or so. This morning Stryd gave 5.24km while the GPS watches gave 5.02 and 5.01 respectively.
This wasn't the first time out with the Stryd. Several runs on a 400m track and a couple of other trails runs should have seen it calibrated by now. I haven't looked over earlier runs as I did want to make sure I had a number of different runs with the Stryd.
Let's see how things progress. I have done a couple of runs on a 400m track but not sure if I had the Stryd set up properly so can't comment on that except to say the watches gave the same distance. However, I now have the Stryd where I want it so can. and will, do some more comparison runs to see how this plays out.