Can GPS on a phone, such as iPhone or Android determine your Z coordinates ?
I know it certainly has to be able to determine X and Y, well longitude, latitude that is, but what about the Z coordinates ? Can it determine your height, and can I obtain height relative to ground ?
Height, as measured by a gps, is relative to the WGS84 ellipsoid. The WGS84 is representative of the field where the gravity is the same, the geoid. Not quite the same as the ground.
You can determine altitude with iPhone using CoreLocation http://developer.apple.com/iphone/library/documentation/CoreLocation/Reference/CLLocation_Class/CLLocation/CLLocation.html
Android surely can ... have a look at the features of e.g. MyTracks which include even evaluation profiles.
Altitude, however, is usually measured in "above sealevel", which means, that you could determine the distance from the ground by substracting the ground evaluation from your actual evaluation: ev(ground) - alt = distance(fromGround).
