Fig. 1. System layout

Fig. 2. The flow chart of the detection method for eliminating gas fluctuation

Fig. 3. Fitting for the signal

Fig. 4. The background noise elimination

Fig. 5. Adaptive iterative fitting signal

Fig. 6. Experimental site map

Fig. 7. Accuracy measurement experimental results of source a

Fig. 8. Accuracy measurement experimental results of source b

Fig. 9. Experimental results of source a consistency

Fig. 10. Experimental results of source b consistency

Fig. 11. (a) Experimental site situation, (b)Telescope Experimental site situation

Fig. 12. The methane concentration c-c_b result

Fig. 13. Q measurement result