Fig. 1. Schematic diagram of surface signal

Fig. 2. Three measurement methods. (a) Under-water profiling method; (b) skylight-blocked method; (c) above-water method

Fig. 3. 3D structure diagram of WAOPAS

Fig. 4. Composition diagram of WAOPAS

Fig. 5. Optical path diagrams of radiometer. (a) Radiance radiometer; (b) irradiance radiometer

Fig. 6. Optical path of dispersion unit

Fig. 7. Schematic diagram of Kohler illumination lens

Fig. 8. Optical path diagram of 10° lens

Fig. 9. Diffuse spots of 10° lens

Fig. 10. Cosine response of irradiance radiometer

Fig. 11. Acquisition software of WAOPAS

Fig. 12. Spectral characteristic peak curves. (a) Surface radiance radiometer; (b) sky radiance radiometer; (c) downwelling irradiance radiometer

Fig. 13. Responsivity of WAOPAS. (a) Irradiance radiometer; (b) radiance radiometer

Fig. 14. Schematic diagram of radiometric calibration

Fig. 15. Outdoor comparison experiment. (a) 99% white diffuse panel; (b) 20% grey diffuse panel

Fig. 16. Relative difference. (a) Radiance relative difference; (b) irradiance relative difference