# Event Detection and Spatio-temporal Analysis of Low-Altitude Unstable Approach
## 3 Results and Discussion
### Correlation Analysis between Influential Factors
#### 3.3.2 Geographically-weighted Correlation Coefficient
\begin{table}
\begin{tabular}{c c} \hline \hline
**Wind Level** & **Correlation Coefficient** \\ \hline Breeze & 0.35 \\ Levels 1–2 & 0.5 \\ Levels 3–4 & 0.48 \\ Levels 4–5 & 0.69 \\ Levels 5–6 & 0.38 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Correlation coefficients between UA triggering frequency and wind levels. \begin{table}
\begin{tabular}{c c} \hline \hline
**Function Name** & **Function** \\ \hline Box car & \(w_{ij}=1\) if \(d_{ij}<r\), \\  & \(w_{ij}=0\) otherwise \\ Bi-square & \(w_{ij}=\left(1-\left(\frac{d_{ij}}{r}\right)^{2}\right)^{2}\) if \(d_{ij}<r\), \\  & \(w_{ij}=0\) otherwise \\ Gaussian & \(w_{ij}=\exp\left(-\frac{d_{ij}^{2}}{2\beta^{2}}\right)\) & (11) \\ Exponential & \(w_{ij}=\exp\left(-\frac{d_{ij}}{\beta}\right)\) & (12) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Kernel function equations. that the correlation between UA events and elevation is irrelevant, but more detailed analysis should be done from a spatial perspective. In general, the analysis of global correlation provides a macroscopic view of the relationships between the triggering frequency of UA events and meteorological and topographical factors. However, the analysis results are relatively singular and absolute, and therefore lack a guiding significance for the refined analysis of UA events. It was found that the mean value of the GWCC is positively correlated with the wind level. This is in accordance with the empirical causes of UA events, and indicates that the local correlation coefficients that consider spatial heterogeneity characteristics can better reflect the correlation. Figure 6 presents the estimates of the GWCCs between the triggering frequency of UA and wind levels 5-6. The triggering frequency of the UA of aircraft was found to be correlated to wind levels 5-6 in the Bohai coastal area. In the case of high winds, such conditions would demand an immediate go-around, and a pilot experienced in manual flying can effectively avoid UA events. Figure 7 presents the distribution of the GWCCs between the trigger frequency of UA events and elevation. It was found that the trigger frequency of UA events that affect Airbus aircraft tended to be more correlated with the altitude elevation; the higher the altitude, the higher the trigger frequency of UA events, especially in the western part of China. This phenomenon is in accordance with previous inferences. GWCC, as compared to the traditional global correlation coefficient, can reflect the correlations between factors and can be used to more precisely and objectively analyze the relationships between the objective factors of UA from a local perspective. However, only ESDA methods were utilized in the present work. Detailed phenomena and incentives, such as the use of geographically-weighted models, e.g., geographically-weighted regression [21; 22], must be further studied and explored for the diversified analysis of relative factors. Figure 5: Correlation between UA triggering frequency (Boeing aircraft) and elevation.