# A Police and Insurance Joint Management System Based on High Precision BDS/GPS Positioning
## 4 Key Technologies
### Vehicle Intelligent Terminal
The whole trajectory of the 2 nd Ring Rd is shown Figure 4. It is clear that the GNSS positioning cannot obtain the vehicle's location when it drives on road with noise barriers. Thus it is necessary to use INS. Figure 3: Sketch of the BDS/GPS positioning module. In the test experiments, the reference data is obtained from a POS 620 unit. POS 620 is a GNSS dual antenna fiber gyroscope positioning system which supports multi-GNSS (BDS, GPS and Global Navigation Satellite System (GLONASS)). It applies a six frequency GNSS receiver with high sensitivity, professional level of positioning and attitude heading, multi-channel for tracking GNSS signals and the integrated inertial measurement sensor based on high-precision quartz disturbance accelerometer and fiber gyroscope. The carrier and code pseudo-range measurements provided by the GNSS receiver and the observations of the inertial measurement sensor are combined by using a tight coupling technique. On this basis, the system can provide attitude information such as horizontal attitude and course, positioning information such as longitude, latitude, altitude and others, and inertial measurement information such as three-dimensional acceleration, angular velocity [24]. The positioning accuracy can reach centimeter level with RTK and the performance of IMU is listed in Table 1. Therefore, the POS 620 is selected as the reference in the experiments for its high accuracy. In this article, we show three kinds of test results:  
1. Accuracy evaluation in the lateral direction of the lane  
The location error in the lateral direction of the lane is a key factor to judge whether a vehicle changes lanes or not. The location error of the terminal in the lateral direction of the lane in five tests is shown in Figure 5. The statistics of location error in the lateral direction of the lane are shown in Table 2.  
The total number of epochs of the device in the five tests is 12,721, of which the proportion of the location error less than 0.5 m is 57.5541%; the proportion of the location error less than 1 m is 86.5277%; the proportion of the location error less than 1.5 m is 94.3217%. \begin{table}
\begin{tabular}{c c c} \hline \hline \multicolumn{2}{c}{**Characteristics**} & **Tactical** \\ \hline \multirow{3}{*}{Gyroscope} & bias (1\(\sigma\)) & 0.1\({}^{\circ}\)/h \\  & white noise (ARW) & 0.03\({}^{\circ}\)/\(\sqrt{\text{h}}\) \\  & scale factor (1\(\sigma\)) & 200 ppm \\ \hline \multirow{3}{*}{Accelerometer} & bias (1\(\sigma\)) & 25 mGal \\  & white noise (VRW) & 0.05 \(\frac{\text{m}}{\text{s}}\)/\(\sqrt{\text{h}}\) \\ \cline{1-1}  & scale factor (1\(\sigma\)) & 200 ppm \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Characteristics of the IMU. Figure 4: The whole vehicle trajectory on the 2 nd Ring Rd; (The left one is obtained from GNSS, the right one is obtained from GNSS/INS). 2. Accuracy evaluation of lane change  
The methods used are as follows: (1) display trajectories of the tested equipment and the reference equipment on the high-definition map; (2) make a comparison between the trajectories of tests and on the high definition map and judge whether the time of actively changing lane and its direction are consistent with that on the high definition map; (3) count the successful number of times of lane change and calculate the success rate of lane change. Fifteen instances of active lane changes have been recorded in each test. The statistics for successful number of times of lane change are shown in Table 3, which were obtained by comparison of the screenshots.