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Field-based nonimaging spectroradiometers are often used in vicarious calibration experiments for airborne or spaceborne imaging spectrometers. The calibration uncertainties associated with these ground measurements contribute substantially to the overall modeling error in radiance- or reflectance-based vicarious calibration experiments. Because of(More)
—Field and laboratory goniometers are widely used in the remote sensing community to assess spectrodirectional reflection properties of selected targets. Even when the same target and goniometer system are used, field and laboratory results cannot directly be compared due to inherent differences, mainly in the illumination conditions since actual(More)
In spectrodirectional Remote Sensing (RS) the Earth's surface reflectance characteristics are studied by means of their angular dimensions. Almost all natural surfaces exhibit an individual anisotropic reflectance behaviour due to the contrast between the optical properties of surface elements and background and the geometric surface properties of the(More)
In the remote sensing user community there is a lack of consistency in definitions and properties of reflectance quantities. On one hand, more recent satellite programs such as NASA's MODIS and MISR sensors take into account the directional dimension of the different reflectance products. On the other hand, many published studies still remain unspecific on(More)
Field and laboratory goniometers are widely used in the remote sensing community to assess spectrodirectional reflectance properties of selected targets. Even when the same target and goniometer system are used, field and laboratory results cannot directly be compared due to inherent differences, mainly in the illumination conditions: typically goniometers(More)
Spectrodirectional experiments with goniometer systems are only able to observe approximations of truly directional surface reflectance properties (BRDF). The directly observed quantity in field experiments is called hemispherical directional reflectance factor (HDRF), corresponding to hemi-spherical illumination, which depends on the atmospheric(More)
Analysing databases, field and airborne spectrometer data, modelling studies and publications, it becomes obvious, that there is a lack of consistency in definitions of reflectance quantities throughout the imaging spectroscopy user community. One example is the term 'BRDF' assigned to significantly differing quantities, ranging from the bidirectional(More)
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