Wikitude

calculating the distance to user

hi, I recently started testing wikitude and I think it's the best location based AR sdk in the market right now cause of it's ease of use and it's light . I'm trying to calculate the distance between POIs and the user . I found two functions distanceTo and distanceToUser . if I define a static location and test the distanceTo function it works without any problems . but if I try to use distanceToUser (which I didn't find out how to use it ) like distanceToUser(myGeoLocatin) or myGeoLocation.distanceToUser() none of them work and using it prevents my Json Objects to be loaded . 
I'll be appreciated if you can help me with this . 
thanks