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Proceedings Paper

The Use Of Field Radiometers In Reflectance Factor And Atmospheric Measurements
Author(s): Che Nianzeng; R. D. Jackson; A. L. Phillips; P. N. Slater
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Paper Abstract

This paper discusses field radiometer methods for measuring (1) the reflectance factor of a surface, (2) the ratio of atmospherically scattered to direct irradiance (s/d) at the ground, and (3) the atmospheric extinction coefficient. Calculations show that, under hazy or cloudy conditions, reflectance factor measurements of an unknown surface made in the field with reference to a white panel, both surfaces having nonlambertian characteristics, can differ by up to 6% from laboratory measurements of the unknown surface. This applies to surfaces having reflectance factors greater than 0.05. The error can be reduced to 0.4% if the direct solar component alone is used for the determination. Measurements of surfaces with reflectance factors from 0.09 to 0.4 showed errors of 10% and 2% respec-tively when the total radiance of the target was ratioed to that of the reference panel. These errors can be reduced to 4% and less than 1% respectively when the direct solar components are ratioed. The mid-infrared (mid-IR) bands of a commonly used field radiometer showed a high out-of-field response that gave rise to measurement errors on the order of 20%. The effect of the reflectance of other surfaces in the neighborhood of the target is demonstrated by determining the ratio of shaded to direct irradiances. Agricultural scenes can show changes of about 5% in the red and 20% in the near IR. A commonly available field radiometer, in conjunction with a reference panel, can be used reliably to determine the atmospheric extinction coefficients in broad wavelength intervals.

Paper Details

Date Published: 8 February 1985
PDF: 10 pages
Proc. SPIE 0499, Optical Radiation Measurements, (8 February 1985); doi: 10.1117/12.971070
Show Author Affiliations
Che Nianzeng, Beijing Institute of Technology (United States)
R. D. Jackson, USDA-ARS (United States)
A. L. Phillips, University of Arizona (United States)
P. N. Slater, University of Arizona (United States)

Published in SPIE Proceedings Vol. 0499:
Optical Radiation Measurements
Aaron A. Sanders, Editor(s)

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