## 2 Methodology and Data
### High Precision and Wide Range XCH4 Fusion Dataset Construction
\begin{table}
\begin{tabular}{c c} \hline \hline
**Data Source** & **RMSE** \\ \hline TROPOMI data before fusion & 43.409 ppb \\ Data fitted by linear regression model & 35.024 ppb \\ Data fitted by random forest model & 29.118 ppb \\ Data fitted by local random forest model & 23.201 ppb \\ \hline \hline \end{tabular}
\end{table} 
Table 2: RMSE for TROPOMI Data and Fusion Data from Three Models. Figure 6: Comparison and fitting plots of pre-merger and post-merger data with TCCON station data for each model, where **(a)** shows the pre-merger TROPOMI data compared to the TCCON station data, **(b)** represents the linear regression model, **(c)** represents the localized random forest model, and **(d)** represents the random forest model. false positive features, thereby eliminating their interference with the retrieval results. Subsequently, we applied a matched filter operator to the study area to obtain 30-m high-resolution \(\Delta\)XCH\({}_{4}\) values. Figure 7 presents a representative matched filtering result for a typical section of our study area. This figure shows the temporally averaged results from multiple observations by the GF-5 satellite over the oilfield region on June 20. In the process of matched filtering, we need to average the retrieval results from multiple scenes of GF-5 imagery to obtain the final result. This is because single-scene imagery has a transient nature, and methane emission sources identified from a single scene may not represent persistent sources. Averaging the retrieval results from multiple scenes helps identify continuous emission sources, allowing us to focus on these persistent sources in future work and improve both the efficiency and effectiveness of our efforts. Figure 7b provides the satellite base map for the displayed area, while Figure 7a,c focus on two specific industrial sites within the region. Figure 7e shows the matched filtering results for the entire area, and Figure 7d,f present the results for the two industrial sites. In Figure 7h, the matched filtering results are overlaid onto the satellite base map, with areas lacking XCH\({}_{4}\) enhancement (less than 20 ppb increase) set to null. Figure 7g; display the overlay results and base map images for the two industrial sites. It is evident from the combined analysis of Figure 7a,c,g;i that XCH\({}_{4}\) levels are significantly elevated in the oil and gas industrial areas, particularly in the regions surrounding oil storage tanks. Pronounced methane plumes were observed in the GF-5 imagery after matched filtering. The average XCH\({}_{4}\) enhancement in the oil tank areas reached 176.24 ppb in Figure 7a and 201.33 ppb in Figure 7c. Other parts of the industrial sites, excluding the oil tank areas, showed enhancements of approximately 100 ppb. As seen in Figure 7e, following the masking steps to remove false positives, there is almost no XCH\({}_{4}\) enhancement in the areas outside the industrial sites. Construction of High-Resolution XCH\({}_{4}\) Products for the Oil Field Area and Comparison of High- and Low-Resolution Datasets

In the previous sections, we generated a 7 km resolution, high-precision XCH\({}_{4}\) product using the LRF model. Simultaneously, we fused data from hyperspectral satellites such as GF-5, employing a matched filtering method to obtain 30 m high-resolution \(\Delta\)XCH\({}_{4}\) data for the oilfield regions. Based on these two datasets, we upsampled the 30 m resolution \(\Delta\)XCH\({}_{4}\) dataset to a 1 km resolution and resampled the 0.1\({}^{\circ}\) resolution GFEI inventory

Figure 7: Example of \(\Delta\)XCH\({}_{4}\) Retrieval Results, where (**b**) is a satellite map of the region, (**a,c**) are zoomed presentations of the plant area in (**b**); (**e**) is a map of the matched filter results of the region, and (**d,f**) are zoomed presentations of the same region as in (**a,c**); (**h**) is a display of the matched filter results superimposed on the satellite map and hiding the background values, and (**g.i**) are zoomed presentations of the plant area in (**h**).