GPS Accuracy Data for Android phones
10 m?  You'd be lucky to get that kind of accuracy outdoors.

I'm the developer of Car Dashboard, which is a car home replacement that includes GPS features like speedometer, etc. I have the default minimum GPS accuracy set to 200 m which seems to work pretty good for most users (I also have it adjustable in the settings in case they have issues).  On average, I'd say indoors near a window will get you about 50-100 m accuracy. Outside with nice conditions should get you below 50 m. Indoors without any visual sight to the sky is going to be a dead zone.  The signal is just simply not going to reach you and if it does, it is going to be highly inaccurate. 

This is the resource I use to describe GPS accuracy in my application: 


  GPS accuracy is affected by a number
  of factors, including satellite
  positions, noise in the radio signal,
  atmospheric conditions, and natural
  barriers to the signal. Noise can
  create an error between 1 to 10 meters
  and results from static or
  interference from something near the
  receiver or something on the same
  frequency. Objects such a mountains or
  buildings between the satellite and
  the receiver can also produce error,
  sometimes up to 30 meters. The most
  accurate determination of position
  occurs when the satellite and receiver
  have a clear view of each other and no
  other objects interfere.