Fig. 1. Transmittance variations at different concentrations

Fig. 2. Transmittance changes at different penetration distances

Fig. 3. Variations of bidirectional reflection distribution function with incident angle. (a) curves of \begin{document}${f_r}$\end{document} changing with \begin{document}${\theta _i}$\end{document} at \begin{document}${\theta _r} = {30^ \circ }$\end{document}; (b) curves of \begin{document}${f_r}$\end{document} changing with \begin{document}${\theta _i}$\end{document} at \begin{document}${\theta _r} = {60^ \circ }$\end{document}

Fig. 4. Structure diagram of APD lidar system

Fig. 5. Mean-Shift image tracking flowchart

Fig. 6. UAV trajectory by range profile tracking. (a) Motion trajectory image; (b) Target center trajectory curve

Fig. 7. UAV trajectory by visible light tracking. (a) Motion trajectory image; (b) Target center trajectory curve

Fig. 8. Comparison of range profile tracking and visible light tracking. (a) X-coordinate trajectory; (b) X-coordinate angle radian curve; (c) Y-coordinate trajectory; (d) Y-coordinate angle radian curve

Fig. 9. Range profile of UAV in smoke scenes

Fig. 10. Smoke filtering UAV range profile

Fig. 11. Partial imaging sequence under the background of firelight mutation

Fig. 12. Range profile tracking trajectory of UAV. (a) Motion trajectory image; (b) Y-coordinate trajectory curve

Fig. 13. Target range profile tracking trajectory after filtering out firelight. (a) Tracking trajectory image; (b) Y-coordinate trajectory curve