Abstract

Sky luminance distributions for the upper and lower sky at ground level, 1.52 km and 6.10 km are presented for a clear day with a medium high sun. The directional luminous reflectances of a variety of natural terrains and man-made surfaces measured under a clear sky with a moderately high sun are also presented. These data are applicable for use in visibility calculations and supplement the data presented in an earlier article [ S. Q. Duntley, J. I. Gordon, John H. Taylor, C. T. White, A. R. Boileau, J. E. Tyler, R. W. Austin, and J. L. Harris, Appl. Opt. 3, 549 ( 1964)].

© 1966 Optical Society of America

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References

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  1. S. Q. Duntley, J. I. Gordon, John N. Taylor, C. T. White, A. R. Boileau, J. E. Tyler, R. W. Austin, J. L. Harris, Appl. Opt. 3, 549, (1964), Sec. II, Sec. III and Sec. VI.
    [CrossRef]
  2. A. R. Boileau, J. I. Gordon, Appl. Opt. 5, 803 (1966).
    [CrossRef] [PubMed]
  3. J. I. Gordon, P. V. Church, “Overcast Sky Luminances and Directional Luminous Reflectances of Objects and Backgrounds under Overcast Skies” 6,June (1966).
  4. E. L. Krinov, “Spectral Reflectance Properties of Natural Formations,” Acad. Sci. USSR, G. Belkov, Aero Methods Lab. (1947) [English transl.: Tech. Trans. TT-439, Natl. Res. Council Canada (1953)].

1966 (2)

A. R. Boileau, J. I. Gordon, Appl. Opt. 5, 803 (1966).
[CrossRef] [PubMed]

J. I. Gordon, P. V. Church, “Overcast Sky Luminances and Directional Luminous Reflectances of Objects and Backgrounds under Overcast Skies” 6,June (1966).

1964 (1)

Austin, R. W.

Boileau, A. R.

Church, P. V.

J. I. Gordon, P. V. Church, “Overcast Sky Luminances and Directional Luminous Reflectances of Objects and Backgrounds under Overcast Skies” 6,June (1966).

Duntley, S. Q.

Gordon, J. I.

Harris, J. L.

Krinov, E. L.

E. L. Krinov, “Spectral Reflectance Properties of Natural Formations,” Acad. Sci. USSR, G. Belkov, Aero Methods Lab. (1947) [English transl.: Tech. Trans. TT-439, Natl. Res. Council Canada (1953)].

Taylor, John N.

Tyler, J. E.

White, C. T.

Appl. Opt. (2)

Overcast Sky Luminances and Directional Luminous Reflectances of Objects and Backgrounds under Overcast Skies (1)

J. I. Gordon, P. V. Church, “Overcast Sky Luminances and Directional Luminous Reflectances of Objects and Backgrounds under Overcast Skies” 6,June (1966).

Other (1)

E. L. Krinov, “Spectral Reflectance Properties of Natural Formations,” Acad. Sci. USSR, G. Belkov, Aero Methods Lab. (1947) [English transl.: Tech. Trans. TT-439, Natl. Res. Council Canada (1953)].

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Figures (4)

Fig. 1
Fig. 1

Upper and lower sky luminance in ft-L (luminance values multiplied by 10.76 give values in apostilbs) for ground level. Apparent luminance of the sun was 2.79 × 108 ft-L (2.24 × 109 apostilbs). The total illuminance contributed by the upper sky and sun was 5940 lm/ft2 (64,000 lm/m2). The upwelling illuminance from the lower sky was 203 lm/ft2 (2180 lm/m2).

Fig. 2
Fig. 2

Upper and lower sky luminance in ft-L (luminance values multiplied by 10.76 give values in apostilbs) for 1.52 km. The apparent luminance of the sun was 4.45 × 108 ft-L (4.79 × 109 apostilbs). The total illuminance contributed by the upper sky and sun was 8170 lm/ft2 (87,900 lm/m2). The upwelling illuminance from the lower sky was 560 lm/ft2 (6020 lm/m2).

Fig. 3
Fig. 3

Upper and lower sky luminance in ft-L (luminance values multiplied by 10.76 give values in apostilbs) for 6.10 km. The apparent luminance of the sun was 5.05 × 108 ft-L (5.43 × 109 apostilbs). The total illuminance contributed by the upper sky and sun was 8730 lm/ft2 (93,900 lm/m2). The upwelling illuminance from the lower sky was 952 lm/ft2 (10,200 lm/m2).

Fig. 4
Fig. 4

Position of surfaces appropriate to five azimuths of the path of sight relative to the sun. The two numbers in each surface indicate the zenith angle, and azimuth relative to the sun of the normal from the surface.

Tables (4)

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Table I Directional Luminous Reflectance of Terrain Backgrounds

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Table II Unidirectional Luminous Reflectance of Terrain Backgrounds: the Vertically Downward Path of Sighta

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Table III Unidirectional Luminous Reflectance of Terrain Backgrounds: Azimuth of Path of Sight Perpendicular to Suna

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Table IV Directional Luminous Reflectance of Objects

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