基于实测光谱指数法的ASTER遥感数据岩性信息提取

目前，光谱波段比值法可以用于岩性信息提取与识别。以新疆北山坡北造山带辉长岩、橄榄岩、橄榄辉长岩以及闪长岩为研究对象，深入分析这四种岩性在VNIR（可见光-近红外）-SWIR（短波红外）谱域的光谱差异。基于辉长岩、橄榄辉长岩、橄榄岩以及闪长岩在2 300 nm附近存在-OH的吸收特征，建立了第8波段的相对吸收深度RBD₈；基于橄榄辉长岩、橄榄岩以及闪长岩在400~700 nm出现的弱吸收特征，建立比值指数RI₂₁来反映四种岩性含Fe³⁺矿物的丰度；基于四种岩性在1 100 nm附近都存在由Fe²⁺引起的宽而强的吸收谱带，建立了比值指数RI₅₄来估计Fe²⁺含量。利用RBD₈、RI₂₁以及RI₅₄三个比值指数分别对影像进行增强处理，并对增强后的影像进行RGB彩色合成，不仅识别和提取出辉长岩、橄榄岩、橄榄辉长岩和闪长岩，还有效区分出片岩以及碳酸盐岩等岩性信息。

Lithologic Information Extraction from ASTER Remote Sensing Data Based on Spectral Ratio Method

At present, the spectral bands ratio method can be used for extracting and recognizing the lithologic information.In this paper, the gabbro, peridotite, olive gabbro, and diorite in the north slope of north orogenic belt in Xinjiang are selected as the research object, we deeply analyze the difference of the four kinds of lithology in VNIR-SWIR spectrum domain. On account of the -OH absorption characteristic of the gabbro, olive gabbro, and peridotite diorite in the near 2 300 nm spectrum, we establish the relative absorption depth data of band 8, which is called RBD₈.On the strength of the weak absorption characteristics of the olive gabbro, peridotite diorite and between 400 nm to 700 nm in the spectrum, we establish the RI₂₁ ratio index to reflect the abundance of the four kinds of lithologies, which contain Fe³⁺. Because of the wide and strong absorption band of the four kinds of lithology near 1 100 nm in the spectrum caused by Fe²⁺, we establish the ratio index, which is called as RI₅₄ to estimate the content of Fe²⁺.Using ratio indexes RBD₈, RI₂₁ and RI₅₄ to enhance the image, respectively, we enhance image for the RGB color composite.We not only identify and extract the gabbro, peridotite, olive gabbro, and diorite, but also effectively distinguish the lithology information between schist and carbonate rock.Because of the wide and strong absorption band of the four kinds of lithology near 1 100 nm in the spectrum caused by Fe²⁺, we establish the ratio index which is called RI₅₄ to estimate thecontent of Fe²⁺.