Multipath is one of the dominant error sources of code tracking in indoor

urban district and other harsh environments.In order to eliminate multipath interference

a BAP-UKF method is introduced to estimate the multipath parameters of the weak GPS signal.For suppressing noise

interference and improving the signal to noise ratio

this method uses an block-averaging signal pre-processing method to process the received weak GPS signal.The signal after pre-processed through the multipath correlators.The in-phase or quadrature phase values are used as the observational measurements of unscented Kalman filter to estimate the code tracking’s multipath parameters such as amplitude

code delay

phase

carrier Doppler.The simulation results show that this method can effectively estimate multipath parameters of weak GPS signal

which carry noise ratio is down to 21dB-Hz

so it proves the effectiveness of this method.