Ground radiometry and airborne multispectral survey of bare soils

Abstract

Results are presented from studies of bare soils conducted during the NERC MSS-82, -83 and -84 campaigns. Test areas throughout southern and eastern England were selected to represent a wide range of British soils, and data from these sites are discussed in relation to the problems of intercalibrating ground and airborne data, as well as the effects of solar-sensor geometry on such intercalibration.Natural ground targets were used to intercalibrate the airborne data with ground radiometric measurements, and this was generally successful for non-soil surfaces in bands 3, 5 and 7 of the airborne scanner (Daedalus AADS 1268ATM). Results from band 9 were less satisfactory, possibly due to mismatch between the band sensed by the scanner and that measured on the ground.Soil surfaces showed significant across-track variations in reflectance, and this is related to spectral reflectance indicatrices measured at ground level which show considerable departures from Lambertian response, primarily in the principal plane. No evidence was found of a forward scattered (specular) component in the reflectedflux. The effectof solar-sensor geometry is further investigated through the study of soil surfaces within cloud shadows, and the observed reduction in variation with viewing angle down-Sun is attributed to the reduction in the directional component of irradiation, and consequent reduction of shadowing.Results are also presented which confirm that under some circumstances management practice can influence remotely sensed data in both the spatial and spectral domains. This is shown through the effect of deep ploughing, which caused a spectrally non-selective reduction in reflectance throughout the region 0,52-1·75 11m, and produced a corrugated microrelief which interacted with the scan-line direction to cause interference fringes on the images.

A simple spectro-goniometer for collection of multiple view angle reflectance factors

“…The results have demonstrated that the approach provides useful data for describing soil surface structure. This result extends earlier multispectral MVA work with soils (Kimes et al 1980, Milton andWebb 1987) into an operational hyperspectral context. Three key points are important for end-users: first, the collimating lens should be used with Downloaded by [University of North Dakota] at 03:05 22 December 2014 the OO instrument, to ensure that data are collected from a well-defined small area on the target.…”

Effects of farming works on soil surface bidirectional reflectance measurements and modelling

“…The results of our experiment, as well as others carried out by Brennan and Bandeen (1970), Kriebel (1976), Kimes and Seller (1985), Walthall et al (1985 ), Milton and Webb (1987), and Irons and Smith (1990 ), show that the soil surface NR variation along the SPP in the view zenith angle h v function depends most strongly on the solar zenith angle h s , independent of its roughness state. To minimize the in uence of the h s on the variation of the NR curve shape, caused by the soil surfaces roughness, only the curves for which data were collected at similar solar zenith angles can be directly analysed together, as presented in gure 6.…”

Bidirectional reflectance of bare soil surfaces in the visible and near‐infrared range

“…The reflectance of bare soil in the visible and near-infrared range has mainly been discussed as a background for spectral response of vegetative surfaces (Brennan and Bandeen, 1970;Kriebel, 1976;Eaton and Dimhirn, 1979;Ott et al, 1984;Curran, 1985;Bartlett et al, 1986;Huete, 1987;Milton and Webb, 1987;Foody, 1988;Deering et al, 1990). Remotely sensed data on the soil surface, like vegetation canopies, demonstrate non-Lambertian reflectance properties.…”

“…If position of irregularities of a rough surface makes it impossible to illuminate the whole surface directly, its shadowing becomes another important factor influencing the shape of the surface reradiation pattern (Graetz and Gentle, 1982;Cooper and Smith, 1985;Ranson et al, 1985;Huete, 1987;Milton and Webb, 1987;Cierniewski, 1987Cierniewski, , 1989Irons et al, 1992). The degree of surface shadowing depends on the density of those elements which cast the shadow, the microconfiguration of the surface, and its slope in relation to the incident rays.…”