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8 February 1985 The Use Of Field Radiometers In Reflectance Factor And Atmospheric Measurements
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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.
© (1985) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Che Nianzeng, R. D. Jackson, A. L. Phillips, and P. N. Slater "The Use Of Field Radiometers In Reflectance Factor And Atmospheric Measurements", Proc. SPIE 0499, Optical Radiation Measurements, (8 February 1985); https://doi.org/10.1117/12.971070
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