In pedestrian dead reckoning（ PDR）

a position correction method based on Wi Fi-aided is proposed to eliminate inertial accumulation error. When the pedestrian reaches the access point（ AP） where the signal strength is greater than a certain threshold

the positioning coordinate is reset to the coordinate of the AP. In addition

In the current PDR algorithm

the precision of step size estimation is low and the universality is poor

a Wi Fi-aided dynamic adjustment method of frequency-step model is proposed. When the RSSI of Wi Fi is lower than the set threshold

the real-time frequency was calculated by fast Fourier transform（ FFT） on the sum acceleration

and to estimate step size through the frequency-step model; when the received signal strength indication（ RSSI） of Wi Fi reaches a set threshold two times successive

the frequency estimation step and Wi Fi estimation step are weighted according to the RSSI to obtain the fusion step size

the parameters of the frequency-step model are feedback adjustment on the base of fusion step size

the adjusted model for the next phase of PDR. In order to verify the above methods

the experiment is designed in electrical building

the result shows that the position correction effectively eliminates the accumulated error of inertial sensors

and the PDR error is reduced by more than 20 %after the adjustment of the model parameters.