Fig. 1. Definition of emission flux

Fig. 2. Schematic of near-infrared spectral telemetry system

Fig. 3. Four gas absorption lines intensity at 1590-1620 nm

Fig. 4. Absorption cross section of three gases. (a) CO₂; (b) CH₄; (c) H₂O

Fig. 5. Selected different reference spectrum and spectrum fitting results of CO₂ retrival. (a) Reference spectrum in the zenith direction (90°) and measured spectrum in the target area; (b) reference spectrum in the upwind direction and measured spectrum in the target area; (c) CO₂ fitting effect of selecting the reference spectrum in the zenith direction; (d) CO₂ fitting effect of selecting the reference spectrum in the upwind direction

Fig. 6. Example of CO₂ retrieved by DOAS. (a) Measured spectrum and reference spectrum; (b) CO₂ fitting differential optical density; (c) residual error after fitting

Fig. 7. Principle of 16-point convolution bicubic interpolation method

Fig. 8. Field observation map of a power plant in Feidong. (a) Two-dimensional motor platform,telescope, and fiber; (b) spectrometer and computer

Fig. 9. DSCD distribution of CO₂ around the power plant in Feidong (deducted the background)

Fig. 10. Variation of CO₂ concentration with horizontal distance at different heights above the chimney

Fig. 11. Two-dimensional distribution of CO₂ DSCD interpolation in the power plant in Feidong (deducted the background)

Fig. 12. Observation map of Hefei boundary layer

Fig. 13. Two-dimensional distribution of CO₂ DSCD of Hefei (deducted the complex background)