For running races of up to 4 hours, my Garmin Forerunner 610 has been my GPS of choice. It's compact, relatively light, fits well on my wrist, and has decent recording accuracy. I have a wrist strap for the Edge 500, but that unit is cumbersome for a wrist-mount. And my iPhone is too heavy.
DCRainmaker image of Forerunner 610. See his review here.
The issue with the Forerunner is it's very finicky. Here's what I did today during the Dolphin South End Runner's Club San Bruno Mountain "12 km" trail run (actually closer to 13 km, according to my GPS data).
- Turn on, acquiring GPS signal during warm-up run.
- Run with the GPS on, to record warm-up run.
- Finish warm-up run, then hit "stop" and "reset", to lock in the warm-up as a separate activity. Don't turn off the 610: intent is to keep GPS signal active so I'm ready to go at race start.
- Approximately 10 minutes later, with 10 seconds to go before race start, hit "start" to record a new activity.
- Run race
Seems reasonable, right? WRONG. Mega-fail. You'll start your run, the timer will be ticking away, but the distance will be stuck at 0. The reason is that the Forerunner, when it's not recording data concludes it has no use for GPS, and goes into "power save" mode by discarding its GPS connection. There's a way, I think, to tell it to re-acquire, but I can never figure that out, and the touch screen doesn't work so well anyway, so the simplest approach is to power it off then back on again, hoping it acquires GPS while I'm running, and then hit start when it finally does.
This is the second time in a race this year that I've done this. The real cost is in Strava, where I don't match Strava segments on climbs at the opening of the race. For example, today was a 12 km race and a 5 km race. Both courses did the 5 km loop, the 12 km group moving on to an additional loop. I'd have liked to compare my time on the opening loop (which is a Strava segment) to not only those doing the 12 km course, whom I ran with (I was 7th at this point, passing two of them later to finish 5th), but also those in the 5 km race.
But no luck. The data from the opening 500 meters or so are lost.
Instead what you need to do is turn it on for warm-up, but if you want to isolate that as a separate activity, turn it off, reset, then turn it immediately back on, to avoid it going into power-save mode, which it does only after a fixed delay. It actually issues a warning for a few seconds before shutting off GPS, but it's easily missed in the noisy environment of a race start.
I understand why they do this. As frustrating as it is to lose data at the beginning of the run in addition to the unit taking a lot of attention which is far better devoted to the actual race, it's equally frustrating to realize your battery is half-drained away when you need more to get through the race duration. But the present "solution" is too error-prone.
Other than the limited battery life (not enough for hilly ultras) I like it: it records data, it tells me my pace and distance, I can upload at the end of the ride. That's all I want, really. This business with dropping GPS is the biggest flaw.