Am I right in thinking that the GPS on my Suunto measures horizontal distance only; so if for example I ran up a hill at 45 deg (granted extreme example) for 1.4km it would only register 1km?
and does that therefore make a footpod better???
I friend of mine has Nike foodpod thing that connects to her ipod. I have a Forerunning 305. We ran 1 mile (per the 305) to calibrate the ipod. Then ran another (the same) mile with both devices measuring distance. Her's went about another 30m than the 305 before it called it a mile. Pretty flat ground.
30m error from 1600m is pretty good accuracy for the accelerometer (foot pod)...1.8% error.
The foot pod reacts faster to changes in speed than GPS does (intervals), and yep...the GPS will measure your running distance on a flat surface only.
GPS is pretty inaccurate at measureing changes in heights, that's why most devices have a built in altimeter. but the data from the altimeter is not used for the distance calculation.