Using Garmin GPS to measure distance covered ….accurate on hilly routes?

I'm a GPS newbie and just started to use my etrex H . Can anyone confirm whether GPS's are able to take into consideration altitude changes when calculating distance covered ?
e.g if ponts A and B were 1km apart as the crow flies but in between was a mountain would it take into consideration the extra distance required to go up and down (if you know what I mean).
thanks
Bill

I suppose the way to find out would be to find a tall building , get in the lift then start a tracklog whilst heading to the top floor. If the lift travelled 100 metres would it show 100m or 0?

If you run the route back with say Tracklogs, the mapping software will make an approximation. If your GPS has got a built in altimeter you can choose to use that data instead of the map data.

dont think the lift thing will work

I assume it works by knowing your location comparing it to a known Topo and then working out distance due to location.

It would not be able to do speed accuarately either if it was not taking this into account as a very steep hill covers limited linear distance

In answer to your question…yes.
But different GPS's have different accuracy, built in pressure alimeters etc.

Using mine against a bike speedo and the difference is marginal!

this has been covered before. In short, it doesn't take into account the extra distance but it makes naff all difference. Even if the entire distance was up a 1 in 3 hill, it would be out by 5%.

hmmm not so sure Horatio ..but I'm not a mathmetician.

Not sure about not making a difference; as I've a ForeTrek Garmin and on Sunday in the North Downs I measured 19.0miles on it while a buddy measured it at 19.9miles on his bike computer. In more hilly terrain the difference is usually more than 10%.

gps works essentially by traingulation, but with more points ( if that makes any sense! ). up,down or around and about, all dimensions are treated equally as far as i am aware. may not be mega acurate but should be pretty good assuming decent sattelite coverage.