# Research on GNSS/IMU/Visual Fusion Positioning Based on Adaptive Filtering
## 3 Experimental Analysis and Results
### Experimental Results  
To avoid experimental randomness, six sets of experiments were conducted. The experimental sites were chosen as a basketball court and a football field, with the experiments conducted during the afternoon to evening period. Based on the experimental environment, the six sets of experiments were divided into two groups: obstructed and unobstructed, with three sets in each group. The unobstructed group received more usable satellites, and the ample lighting facilitated the selection of keyframes by the camera. In contrast, the obstructed group had fewer usable satellites, and the dim lighting hindered the selection of keyframes by the camera. Different experimental environments were set up to observe and analyze the feasibility and robustness of GNSS, IMU, and visual sensor fusion under varying conditions. The satellite positioning results, GNSS/IMU integrated positioning results, and GNSS/IMU/visual fusion positioning results were analyzed and compared. The position trajectory solution for one set of data is shown in Figure 4.  
Based on Table 1, the single-point positioning data collected by the mobile satellite receiver exhibits an excessive upward positioning error, exceeding 15 m. Therefore, subsequent analyses do not consider the vertical error. After analyzing and processing these six sets of collected data, the results include satellite positioning, GNSS/IMU integrated positioning, and GNSS/IMU/visual fusion positioning. The results obtained from these \begin{table}
\begin{tabular}{c c c} \hline
**Sensor** & **Parameter** & **Technical data** \\ \hline \multirow{5}{*}{Bosch BMI 260} & Programmable measurement range & \(\begin{array}{c}(\mathrm{A}):[\pm 2\,\mathrm{g},\pm 16\,\mathrm{g}]\\ (\mathrm{G}):[\pm 125\,\mathrm{dps},\pm 2000\,\mathrm{dps}]\\ (\mathrm{A}):\pm 20\,\mathrm{m}\end{array}\) \\  & Zero bias & \(\begin{array}{c}(\mathrm{G}):\pm 0.5\,\mathrm{dps}\end{array}\) \\  & Sensitivity error & \(\begin{array}{c}(\mathrm{A}):\pm 0.4\%\end{array}\) \\  & Noise density & \(\begin{array}{c}(\mathrm{A}):\pm 160\,\mathrm{\SIUnitSymbolMicro g}/\sqrt{\mathrm{Hz}} \\ (\mathrm{G}):\pm 0.008\,\mathrm{dps}/\sqrt{\mathrm{Hz}}\end{array}\) \\ \hline \multirow{5}{*}{Hi 1105} & Eastward positioning & \multirow{2}{*}{\begin{tabular}{c} 5.5779 m \\ accuracy (SPP) \\ \end{tabular} } \\  & Northward positioning & \multirow{2}{*}{\begin{tabular}{c} 6.0365 m \\ 6.0365 m \\ \end{tabular} } \\  & Upward positioning & \multirow{2}{*}{\begin{tabular}{c} 15.9024 m \\ \end{tabular} } \\  & accuracy (SPP) & & \\ \hline \multirow{5}{*}{Xtion} & Eastward positioning & \multirow{2}{*}{\begin{tabular}{c} 1.5912 m \\ \end{tabular} } \\  & accuracy (after & \multirow{2}{*}{\begin{tabular}{c} 2.3898 m \\ \end{tabular} } \\  & Northern positioning & \multirow{2}{*}{\begin{tabular}{c} 0.1 m \\ \end{tabular} } \\  & accuracy (after & \multirow{2}{*}{\begin{tabular}{c} 0.1 m \\ \end{tabular} } \\  & correction) & \\ \hline \multirow{5}{*}{BD930} & Eastward positioning & \multirow{2}{*}{\begin{tabular}{c} 0.1 m \\ \end{tabular} } \\  & accuracy (differential & \multirow{2}{*}{\begin{tabular}{c} 0.1 m \\ \end{tabular} } \\  & Notify/visual fusion positioning & \multirow{2}{*}{\
\begin{tabular}{c} 0.1 m \\ \end{tabular} } \\  & accuracy (differential & \multirow{2}{*}{
\begin{tabular}{c} 0.1 m \\ \end{tabular} } \\  & positioning) & \\ \hline \end{tabular}
\end{table} 
Table 1: Sensor parameters. three positioning methods are compared with the ground truth to obtain the Standard Deviation (STD) and Root Mean Square Error (RMSE), as shown in Tables 2 and 3. \[e_{STD}=\sqrt{e_{STD/E}^{2}+e_{STD/N}^{2}} \tag{14}\]  
where \(e_{STD}\) represents the overall STD; \(e_{STD/E}\) represents the eastward STD; \(e_{STD/N}\) represents the northward STD. Similarly, the RMSE can be obtained. From Tables 2 and 3, it can be observed that both satellite positioning and GNSS/IMU integrated positioning achieve satisfactory results in unobstructed environments.