We present ground reference measurements of the directional scattering properties of conifer needles. As the development of multiangular remote sensing instruments sets a growing need for reliable ground reference measurement techniques and databases, there is an increasing demand for data on the spectral properties of conifer needles in forest reflectance modeling and the inversion of physically based models. These data are scarce due to technical and conceptual problems related to measuring thin needles, and the needle directional spectral properties are currently nonexistent even for single wavelengths. We present results from measuring the monochromatic backscattering of Scots pine needles in a controlled laboratory environment; we feel these results of the hot spot signatures of individual conifer needles are unique. The experiment was conducted at with an instrument constructed specifically for backscatter measurement, based on techniques commonly used for laser backscattering measurements and CCD photometry. Strong backscattering peaks near 0° were observed for the needles, the amplitude of the brightening being up to approximately 40%.
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