# GNSS-Assisted Visual Dynamic Localization Method in Unknown Environments
## 6 Conclusions  
Autonomous navigation is the core technology for achieving an intelligent level of unmanned environment perception and autonomous control, navigation, and positioning, which are the foundations of an unmanned system's intelligence [24; 25; 26; 27; 28]. Under an unknown environment, relying on intermittent GNSS position-assisted visual dynamic positioning can provide reliable and continuous global position services for unmanned carriers. In this paper, the GNSS-aided visual dynamic positioning method in unknown environments was investigated using three frames of images and their corresponding GNSS coordinates as constraint data. The main innovation was that the algorithm in this study required only three frames of image GNSS coordinates for global position services. Moreover, the GNSS continuous-aided positioning could suppress the accumulation of visual positioning errors and provide continuous and stable navigation position services. Both the dataset experiments and real data validation showed that although the GNSS initial-aided positioning error and GNSS continuous-aided positioning error both appeared larger and larger over time, in general, the GNSS continuous-aided positioning had an error of no more than 0.3 m in the horizontal direction and no more than 0.5 m in the state estimation in the altitude direction, and this could meet the navigation requirements. Compared with the results of the GNSS initial-assisted positioning, the average absolute error and root mean square error of the GNSS continuous-aided positioning declined by two to three times, and the maximum error was not more than 0.4 m. The accuracy of the GNSS continuous-aided positioning could satisfy the requirements of the continuous positioning services, and it also proved the availability and continuity of the algorithm used in this study.  
In summary, the proposed algorithm can provide continuous and stable location services. Compared with the GNSS initial-aided positioning results, the GNSS continuous-aided positioning accuracy was significantly improved. The next step is to consider the introduction of GNSS original observation data, and the optimization must have three frames of GNSS coordinates as constraint requirements.  
[PERSON], [PERSON], [PERSON], [PERSON], [PERSON] and [PERSON] conceived and designed this study; [PERSON], [PERSON], [PERSON] and [PERSON] performed the experiments; [PERSON] wrote the manuscript; [PERSON] and [PERSON] corrected the grammar errors and formatted the manuscript. All authors have read and agreed to the published version of the manuscript.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Error** & & **MAE/m** & **RMSE/m** & **MAKE/m** \\ \hline \multirow{3}{*}{GNSS initial-aided positioning errors} & x & 0.3521 & 0.2686 & 0.9418 \\  & y & 0.3492 & 0.1960 & 0.7052 \\ \cline{1-1}  & z & 0.5338 & 0.4157 & 1.4509 \\ \cline{1-1}  & x & 0.1016 & 0.0943 & 0.1823 \\ \cline{1-1}  & y & 0.0959 & 0.0704 & 0.1531 \\ \cline{1-1}  & z & 0.1650 & 0.1807 & 0.3005 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Error statistics results.  
**Funding:** This work was supported by the Scientific Research Team Plan of the Zhengzhou University of Aeronautics (23 ZHTD01010). The research was supported by the Science and Technology Department of Henan Province through the project Research on Key Technologies for the Fully Autonomous Operation of Multi-Rotor Agricultural Plant Protection UAVs (no. 222102110029) and the project Research on key technology of intelligent air-ground unmanned systems for autonomous co-operation and high dynamic tracking and landing (no. 242102210028).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data that support the findings of this study are available from the corresponding author upon reasonable request. The data are not publicly available due to privacy.  
**Conflicts of Interest:** The authors declare no conflict of interest.