Determining land use patterns through man-machine analysis of LANDSAT data: A tutorial simulation

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Extension of Laboratory-Measured Soil Spectra to Field Conditions

Spectral responses of two glaciated soils, Chalmers silty clay loam and Fincastle silt loam, formed under prairie grass and forest vegetation, respectively, were measured both in the laboratory under controlled moisture equilibria, and in the field under various moisture and crop residue conditions. An Exotech Model 20C spectroradiometer was used to obtain spectral data in the laboratory under artificial illumination. Reflectance measurements ranged from 0.52-to 2.32-µm in 0.01 µm increments. Asbestos tension tables were used to maintain a 0.10-bar moisture equilibrium following saturation of crushed, sieved soil samples. The same spectroradiometer was used outdoors under solar illumination to obtain spectral response from dry and moistened field plots with and without corn residue cover, representing the two different soils. Results indicate that laboratory-measured spectra of moist soil are directly proportional to the spectral response of that same field-measured moist bare soil over the 0.52- to 1.75-µm wavelength range. The magnitudes of difference in spectral response between identically treated Chalmers and Fincastle soils are greatest in the 0.64-to 0.8-µm transition region between the visible and near infrared, regardless of field condition or laboratory preparation studied

Fine Structure in the Spectral Reflectance of Vegetation and Soils

The spectral reflective response of plants, soils, and rocks may contain information concentrated in relatively narrow spectral regions defined by the light absorption properties of the constituent atoms and molecules. The hope exists that such information will be of value in remote sensing in discriminating information classes, in identifying growth stages and stress conditions in crops, and in delineating the chemical and physical properties of soils and rocks. Satellite sensors measuring spectral regions possibly as narrow as 0.02 µm, a spectral resolution significantly better than that (0.1 µm) of the Landsat multispectral scanner, appear feasible. Fine structure in crop spectra has been reported by Collins who identified a shift in the radiance of wheat measured in the far red (near-infrared 0.73 µm) wavelengths, a shift that occurs at the onset of heading. Wiersma grouped spectra from bare soil and vegetation and found a significant amount of non-redundant information in the near-infrared wavelength region in bands 0.02 µm apart. The paper addresses the key issue raised by Wiersma; if there is information in narrow wavelength bands in reflectance spectra of bare soil and vegetation, is that information attributable to properties of the soil, the vegetation, or both. Four hundred eighty-one spectra representing soils from throughout the United States were analyzed. More than 1000 wheat spectra from four fields measured at four growth stages, several view directions, and several illumination angles were analyzed. The analyses involved the correlation coefficient computed for the spectral reflectance of adjacent wavelengths 0.02 µm apart. The analysis results show clearly the large water absorption bands at 1.4 and 1.9 µm, prominent in soil and vegetation spectra, The iron oxide absorption band at 0.9 µm is quite pronounced in the analysis results of the soils data. The vegetation analysis results show clearly the transition wavelength region between the visible and the near-infrared, anomalies at 0.53 and 0.57 µm, and minor water absorption bands at 0.95 and 1.15 µm. At three wavelengths, 0.85, 1.05, and 1.25 µm, small anomalies in the results may indicate fine structure in the reflectance data but the finding is tenuous at best