Young Su Cho

Observability analysis of the INS/GPS navigation system on the measurements in land vehicle applications

In this paper, the observability of the INS/GPS navigation system for a land vehicle is analyzed on measurements and different dimension filters with respect to the measurements are designed. In the stationary case, it is shown that the horizontal accelerometer biases and vertical attitude errors and gyro biases are unobservable. An 8 th filter is designed based on the observability analysis. When GPS signal is available, a 15 th filter is used with position and velocity measurements. To estimate the INS errors even in the case that GPS signal is blocked a filter is designed in consideration of the non-holonomic constraints of a land vehicle. In this case, the horizontal position and velocity errors and vertical attitude error are unobservable. However, a 12 th filter including the velocity states is designed to estimate the accelerometer biases. Based on the results of the observability analysis and the different dimension filters, an efficient INS/GPS filter including the filters as sub-filters can be designed.

The effect on tracking loop performance when using the efficient search method for fast fine frequency acquisition

When implementing real-time software based GNSS receiver, the accurate and fast signal acquisition and tracking method is more necessary than the hardware based receiver owing to lots of computation time. Generally, in the software based GNSS receiver, parallel code phase signal acquisition method using FFT has been used. But it has the defect of the limited frequency resolution according to input datas length. Considering the carrier frequency resolution must be about tens of Hz in order to perform the tracking loop correctly, the fine frequency acquisition method to minimize the computation time should be necessary to overcome this limitation. Also the examination whether the method will enhance the tracking loops performance and cause the reduction of computation time should be necessary. To evaluate these necessities, in this paper, the efficient search method for fine frequency acquisition will be suggested and tested. Furthermore, the effect on signal tracking loop, when the result of signal acquisition obtained by the suggested method is applied, will be analyzed.