Method of Processing Closed-Circuit Television Digital Images for Poor Visibility Identification

Abstract

This study proposes a method for identifying poor visibility under adverse weather conditions by processing closed-circuit television (CCTV) digital images. The weighted intensity of the power spectrum (WIPS) was examined to determine its applicability as a value for the identification of poor visibility. The magnitude of WIPS represents the difference in spatial frequencies within the image on the basis of the human contrast sensitivity function. WIPS was calculated by the following image-processing procedure: the spatial frequency of the cutout image was calculated with a two-dimensional Fourier transform, and the power spectrum of the cutout image was calculated; WIPS was totaled at spatial frequencies that ranged from 1.5 to 18 cycles per degree. Two kinds of experiments were performed to determine whether WIPS represented the subjective visibility assessment values (SVAVs) given by the test subjects. Clear linear relationships between WIPS and SVAVs were found in both experiments. In addition, the two correlation lines overlapped within the whole range of WIPS. These results suggest that WIPS may be appropriate for identifying poor visibility by the use of digital images.

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References

Chiba

Ishimoto

and Kajiya

. Spatial and Temporal Changes of Visibility in Blowing Snow and Fog. Proc., 4th International Symposium on Snow Removal and Ice Control Technology, TRB, National Research Council, Washington, D.C., 1996.

Kwon

T. M.

Measurement of Motorist's Relative Visibility Index Through Video Images. Presented at 81st Annual Meeting of the Transportation Research Board, Washington, D.C., 2002.

Hagiwara

Kizaka

and Fujita

. Development of Visibility Assessment Methods with Images Under Foggy Conditions. In Transportation Research Record: Journal of the Transportation Research Board, No. 1862, Transportation Research Board of the National Academies, Washington, D.C., 2004, pp. 95–108.

Campbell

F. W.

and Robson

J. G.

. Application of Fourier Analysis to the Visibility of Gratings. Journal of Physiology, Vol. 197, 1968, pp. 551–566.

Ginsburg

A. P.

Contrast Sensitivity, Drivers’ Visibility, and Vision Standards. In Transportation Research Record 1149, TRB, National Research Council, Washington, D.C., 1987, pp. 32–39.