Assuming your livingroom has a roof......GPS doesn't work indoors. You may get a little signal but that is through windows, not the rest of the building. Elevation accuracy goes to hell with less than ideal reception.
Actually with the new high sensitivity chips, it does work in your livingroom. I was skeptical at first, but set my Vista HCx up in my office at work and then booted up the GIS - the receiver told me I was about 2 offices down (so 30 feet) from where I really was! I don't even have windows. The new chip really makes a huge difference is worth upgrading to.
The track that MtnHermit submitted shows classic multipath error. The patch antenna is normally more resistant to multipath problems but must be horizontal to do so, while the quadhelix, when held vertically, is more susceptible to this problem.