Perceived Visibility Measurement Using the HSI Color Difference Method

다국어 초록 (Multilingual Abstract)

The relationship between the optical measurement and the HSI color difference in color coordinates was investigated in this study. Scenic monitoring was conducted by taking 6 cuts a day in two-hour intervals starting from 8 A.M. and ending at 6 P.M. by using a Pentax PZ-20 automatic camera and an EC72D two-channel time-control unit. Optical monitoring at Gwangju site
included continuous measurement of the light extinction coefficient, bext, the light scattering coefficient,bscat and the light absorption coefficient by using a LPV-2 long-path transmissometer, a Belfort model 1597 integrating nephelometer and a Magee Scientific model AE-14U aethalometer,
respectively. During the monitoring periods, the average HSI color difference (D), hue difference (H), saturation difference (S) and intensity difference (I) were calculated to be 98.3 ± 12.1, 4.2 ± 2.3, 78.5 ± 9.2 and − 58.1 ± 12.5, respectively. The average H was lower than the other differences because of the low average plane angle () of 26.9 ± 10.1 C. On the contrary, S was
the largest contributor to the HSI color difference.
These results indicate that atmospheric haze
does not significantly affect the hue of the sky but dominantly affect the saturation of the sky. The light extinction and the visual range showed non-linear relationships to the HSI color difference.
In addition, the HSI color difference was shown to differentiate variations in visibility more effectively under hazy conditions. As a result, measurements of the HSI color difference are expected to provide more detailed information on the variations of visibility in an urban area where hazy
atmospheres are common.

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