云冈石窟大部分雕凿在长石石英砂岩上， 因受环境、 岩性等因素影响， 目前风化状况严重， 其中主要为粉状风化。 基于高光谱成像技术研究云冈石窟砂岩风化状况的整体有效评估方式， 采集目标物400～1 000 nm的高光谱数据， 采用对数残差法进行归一化处理， 参照归一化处理后的反射率数据， 按照这区间的反射率分布范围将风化程度分为强风化和弱风化。 同时在envi平台下对砂岩的风化状况分布进行分级可视化表述。 将可视化结果与现场病害分布状况比对， 结果表明可视化的表述与实际观测结果基本一致， 高光谱技术可用于砂岩的粉状风化状况估测。

Yungang Grottoes were built in the mid-5th century A.D., and named as a UNESCO World Heritage site in 2001. Most of the grottoes were built on the feldspathic quartz sandstones. They were seriously damaged due to the environmental impact. The main form of the weathering is the powdered weathering. The weathering conditions are generally characterized by electrical sounding, penetration resistance, molecular spectroscopy, etc. However, although these methods can give good results about the weathering conditions for a specified sample or site, they are not suitable for providing a global profile of the weathering conditions. The present paper provides a method for effectively and roundly assessing the overall powdered weathering conditions of the Yungang Grottoes based on hyperspectral imaging. Powdered weathering could change the structure and granularity of the sandstone, and thus change the spectral reflectance of the sandstone surface. Based on the hyperspectral data collected from 400 nm to 1 000 nm and normalized by log residuals method, the powdered weathering conditions of the sandstones were classified into strong weathering and weak weathering. The weathering profile was also mapped in the Envi platform. The mapping images were verified using the measured hyperspectal data of the columns in front of the 9th and 10th grottoes as the examples. The mapping images were substantially fitted to the real observations, showing that hyperspectral imaging can be used to estimate the overall powdered weathering of the sandstones.