AR browsers include those like wikitude, Layar etc that are available for Iphone and Android smartphones .
When you point your camera to a landmark they automatically overlay previously available information for a location over it (e.g. name of a restaurant over its door)
If the accuracy of GPS as states by some is ~ 10 m , how can this be done accurately ?
I mean if they track the location of your phone to display geographically accurate information , a difference of even 2-3 m can cause havoc.
you can check by yourself in the code of mixare, which is an augmented reality browser released under a free software license (GPLv3). The source code is available on github both for android and iPhone.
To answer your question: there are errors, mostly because of the compass readings (digital compasses are unreliable because they pick up every kind of noise). What helps is that you are usually looking to objects that are quite big (buildings etc.) hence the error is not THAT visible to the end user, but it’s still there, trust me 🙂
HTH
Daniele
Disclosure: I am the project leader of mixare and main developer of the android version