That doesn't quite constitute using (overall) signal strength, and neither is it the primary location method. Yes, it is possible to use the carrier phase information as well as the L2 carrier phase (and L1/L2 discrepancy) to get a more accurate fix, but this information is only used to adjust the TDOAs of the PRN signals and compensate for varying ionospheric delays. Signal strength of each satellite is much more affected by random low clouds and even the receiver's immediate environment, than by distance from the satellite. In fact, if your receiver provides an SNR readout for each satellite, you can get an idea about just how dramatically these values are affected by, say, a tree that partially obscures a portion of the sky.