风化及其它类荒漠漆表面层对高光谱分辨率遥感的影响（二）

由地表风化产生的表面覆被层的矿物质，其质地或与它的基岩矿物相似，或十分不同，虽然这类表面层的厚度仅有几微米到几毫米，但它们却完全控制了地面的反射光谱。与此相似，有些由风吹送的尘埃、胶结物或其它附着物在表面形成的外层也是影响遥感反射光谱的重要因素。这种由胶结物形成的表层往往是深色（甚至黑色）的，因为它们通常出现在干旱区，故常称为“荒漠漆（“ｄｅｓｅｒｔｖａｒｎｉｓｈ”）。尽管这些暗色对我们的眼睛并无特别之处，但这类表面层（通常为粘土）在短波红外区（ＳＷＩＲ）具有低反射率的吸收特征，并能据此推断它们的矿物成分。因此，为了要在遥感图象和地面的实际“地质状况”之间建立联系，必须对裸露岩石表面特征具有良好的了解。由于不可能在野外总能找到“新鲜”的岩石表面，因此，人们必需能将“岩石内部”物质的光谱和它“上、下表面”的光谱区分开。本文以西澳大利亚中部依尔干地区（Ｙｉｌｇａｒｎ）为例，研究了该地区深度风化的镁铁质、超基性岩和长英质岩石对光谱的影响。

The Effects of Weathering and Other Varnish-like Coatings on High Spectral Resolution Airborne Imagery (Part two)

Surface weathering preduees coatings of mineral materials which may be similar to, or quite differeflt from, the minerals of the underlying parent rock. These coating are usually only microns to millimeters in thickness, but they completely control the reflectance spectra of the terrain. In a similar way coatings formed from adherence of wind-borne dusts, cemented or not, will also dominate the reflectance spectra as seen in remotely sensed imagery. Cemented coatings are often dark-colored (even black) and are usually termed "desert vanish" from their common occurrence in arid regions. Despite their featureless, dark color to our eyes, these coatings (often clays), show characteristic reflectance minima in the short-wave infrared (SWIR) regions, by which their mineralogical composition can be deduced. Thus to relate remotely sensed imagery to actual ground "geology" reqinres a good knowledge of the surficial character of the exposed rock outcrops. It is not always possible to find "fresh" surfaces in the field, and one must always differentiate "upper-surface" spectre (and also "lower-surface" spectra) from the spectra of the "inner rock" materials. This paper describs the spectral effects in deeply-weatherad Mafic, Ultrabasic, and Felsic Rocks in arid terrains of the central Western Australia.