## 3 Results
### STIL Ranging Accuracy  
Combining the TDC measurement data and the centroid temporal data obtained by streak image processing, we made the comprehensive evaluation of the system ranging accuracy. The data are shown in Table 2. The normalized histogram of 6000 measurement results is shown in Figure 7. Based on the normalized histogram, the system's average ranging time is 38,785.6 ns, corresponding to a relative distance value of 5817 m. The red solid line represents the Gaussian fit applied to the histogram data. According to the fitting results, the distribution of the system's measurement time \(t_{range}^{*}\) follows a normal error distribution, and the fitting yields a standard deviation of \(\sigma_{t}=0.65\) ns. Clearly, this value is smaller than the standard deviation of the TDC measurement time and the streak echo time. This can be attributed to the TDC capturing the time jitter of the optical trigger signal, which has a significant impact on precision in long-distance measurements. This result indicated that the ranging accuracy in the ranging measurements is 0.65 ns. The results in Figure 7 verify the stability and high precision of the system's ranging error performance.  
In comparison to previous work of STIL ranging accuracy [25], which optimized static blur width and achieved a measurement accuracy of 0.06 m indoors and 0.25 m over kilometer-scale outdoor distances, the current study demonstrates significant advancements. The calculated Pearson correlation coefficient between \(\Delta t_{trigger}\) and \(\Delta t_{streak\_echo}\) is \(k=0.7\), and integrating system optimizations, the measurement accuracy improved by 30%. The system ultimately achieved a precision of 0.1 m at a distance of 6 km, a substantial improvement over previous results. These advancements showcase the STIL system's potential for high-precision, long-range measurements, making it highly promising for future applications.  
In summary, the TDC provides precise measurements of the trigger pulse time, while the streak images record the timing information of each echo during the detection. By combining these ranging data, the system can correct measurement errors and achieve  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Ranging Data** & \(\Delta t_{streak\_echo}\) & \(\Delta t_{trigger}\) & \(t_{range}^{*}\) \\ \hline Mean value (ns) & 46.3 & 38,739.3 & 38,785.6 \\ Standard deviation (ns) & 0.93 & 0.70 & 0.65 \\ \hline \hline \end{tabular}
\end{table}
Table 2: The STIL 6 km target ranging results (6000 frames).  
Figure 6: TDC measured timing: Channel 1 measures the \(t_{optical\_trigger}\) (\(\sigma_{1}=0.70\) ns); Channel 2 measures the \(t_{streak\_camera\_trigger}\) (\(\sigma_{2}=48\) ps); the time difference representing the \(\Delta t_{\text{trigger}}\) (\(\sigma=0.70\) ns).  
high-precision ranging. The STIL system not only improves the measurement accuracy but also efficiently acquires multiple echo footprint points, generating more reliable and comprehensive distance spatial distribution information. This demonstrates the powerful and efficient high-precision application potential of streak tube imaging LiDAR. In subsequent applications, the STIL system needs scanning units and GPS units for wide-range, high-efficiency scanning. The precision of these units, along with ranging accuracy, determines the 3D measurement accuracy of the STIL system. Atmospheric conditions can also affect accuracy in long-distance measurements. Nevertheless, high ranging accuracy is essential for the STIL system and critical for its final integrated application.