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在地球科学领域中,自相似性非常普遍,围岩蚀变作为一种地学特征并以遥感异常反映在影像上,其像元亮度—面积模式符合一定的分形理论。利用分形理论的求和法进行遥感蚀变异常的提取和分级可以弥补门限法和灰度直方图目视方法确定突变点的不足,再次利用分形的盒维数方法可得到研究区遥感蚀变异常的分形特征。以云南昭通毛坪铅锌矿ETM+遥感影像数据为信息源,采用主成分分析法(PCA)计算出反映矿区遥感蚀变异常的主分量,再对异常主分量进行像元灰度值和像元个数的统计并采用分形方法对蚀变异常信息进行分析和蚀变异常级别的划分,最后利用分形的盒维数法得到毛坪铅锌矿遥感蚀变异常信息的分形特征并与传统门限化方法进行了对比研究。研究表明区内遥感蚀变异常信息具有统计上的分形特征,分形方法确定异常限要比传统的门限化方法选取蚀变阈值更为准确;分维值与异常级别存在一定的正相关关系;分维高值区与蚀变信息密集区相一致。
In the field of geosciences, self-similarity is very common. Wall rock alteration as a geo-logical feature and remote sensing anomalies are reflected in the image. The pixel brightness-area model conforms to a certain fractal theory. The extraction and classification of remote sensing alteration anomalies by using the summing method of fractal theory can make up for the shortage of mutation points by making use of the threshold method and the grayscale histogram visual method, and again using the fractal box dimension method to obtain the remote sensing alteration anomaly Fractal features. Using principal component analysis (PCA) to calculate the principal component reflecting the remote sensing alteration in the mining area based on the ETM + remote sensing image data of Maoping lead-zinc mine in Zhaotong, Yunnan Province, the gray value and pixel of the anomalous principal component The fractal method was used to analyze the alteration anomaly information and divide the anomalous level of alteration. At last, the fractal features of remotely sensed alteration anomaly information of Mao Ping lead-zinc mine were obtained by fractal box dimension method and compared with the traditional threshold Methods were compared. The study shows that the information of remote sensing alteration anomaly in the area has statistical fractal characteristics. The fractal method is more accurate than the traditional threshold method to select the abnormal threshold. The fractal dimension has a certain positive correlation with the abnormal level. The high-value areas are consistent with the high-density information areas.