Spectral Directional Reflectance Research Articles

An Analysis of Response Curves and Its Application to Directional Spectral Reflectance Measurements

This paper deals with an analysis of the directional reflectance curve s specified by 2 kinds of independent variables, ie. wavelength and spatial direction.Generally, these reflectance curves have been analyzed for each of spatial directions successively, and it was suspected that this usual method was ineffective for utilization of informations contained in these observations.The principle of the present method is based upon the effective combination of principal component analysis and regression analysis, both of which are frequently used in multivariate statistics.The following effectiveness were confirmed by comparing true, observed and estimated spectral reflectance curves in a model experiment:(1) There is a possibility to make a useful estimation of physical meanings which might be hidden behind observed raw data.(2) The estimated spectral reflectance curves by the present method give better fit to the true curves than the raw data.

Verification of a reflectance model for mature corn with applications to corn blight detection

A new model for calculating the directional spectral reflectance of vegetative canopies was verified for the case of mature corn by field reflectance measurements on two different mature corn fields at each of two viewing angles and over the visible and near infrared spectral bands. The application of the model to hypothetical conditions indicates that moderately severe Southern Corn Leaf Blight should be marginally detectable by aerial photography under certain special circumstances and that for more severe blight, the blight condition should be distinguishable from moisture stress. The application of the model to hypothetical fields of young corn indicates that the blight condition should be easily detected under a wide range of circumstances.

Far Infrared Reflectometer for Imperfectly Diffuse Specimens

Apparatus for measurement of spectral directional reflectance in the far infrared between 2–100 μ is described. The reflectometer consists of opposed paraboloids, one on axis with 90° lip angle and a second of longer focal length off axis. A large uniform source beyond a chopper and the focal point of the off-axis paraboloid provides diffuse irradiation onto the sample. Spectral reflectances of diffusing and specular materials measured with the reflectometer attached to prism and grating monochromators are reported. Performance data including stray energy measurements are given, and results of an error analysis are presented.

Minimizing Anomalies in Reflectance Measurements with the Beckman Quartz Spectrophotometer

The Beckman spectrophotometer Model DU has proved to be a useful instrument for measuring spectral directional reflectance. Like other spectrophotometers it is subject to slit-width and stray-energy errors. The magnitude of these errors and techniques for minimizing them are discussed. The viewing geometry and an adaptor for four-inch square specimens are described.