Thinking about buying a Garmin 201 for measuring road loops?

If you live in a very wooded area or an urban area, it won't be very accurate. The old 201s weren't exactly known for their ability to hold a good signal.

Just for open roads. Think Boulder countryside for an example.

There are very good google maps-based apps on android phones and iphones. I record my runs and rides and get pretty accurate pacing info that I can upload onto the web or my computer. And I can mount it on my car dash when I travel. Garmins etc may become obsolete very very soon.

I left out that they use gps just like the navigation systems do.

Since they are just road loops, you can stay at home and map the distance using

http://www.mapmyrun.com/

or

http://www.walkjogrun.net/

- no need to drive anywhere or buy anything.

The GPS units can be a good idea if you are running on unmapped trails, or if you just want to head out the door and run wherever you feel like and know the distance later, but for road loops I don't see the point.

Well I would want to mark out splits. Will it work through the car or should I have it on the outside of the windshield?

Bump.

It should work OK from your dashboard, but you could probably accomplish the same thing with mapping websites, as others have noted.

No I know, I already do that for easy runs, but for workouts where I'd like to be able to mark out mile points and don't want to wheel out a 5 mile loop.

So... you want to run a route, then drive it in your car to find distance?

Just buy a Garmin Forerunner. The older ones should be pretty cheap on eBay.

The 201 is pretty ancient GPS technology and probably not accurate enough for what you have in mind. The jump in accuracy from that to the 205 was quite significant. Also the sample rates on these things are designed for running speeds, not driving speeds. So that's another possible source of inaccuracy. But if you're comfortable with your splits possibly being 10-15 seconds off actuality, go for it.