Remote sensing detection of volcanic ash cloud using independent component analysis

The volcanic ash cloud is mainly composed of volcanic ash debris and gases. The adequate mixture of the two can form acidic aerosols. It not only causes the major global climate and environmental changes,but also seriously threatens the aviation safety. Remote sensing can quickly and accurately obtain the information of the surface's and the atmosphere's changes; therefore it is playing an important role in the monitoring of volcanic activity. In recent years,with the advancement of sensor technology,the thermal infrared remote sensing technology has become an important means of detecting the volcanic ash cloud. However,due to the large amount of spectral bands and data,the remote sensing data have pretty strong band correlation and obvious information redundancy problem, all of which have decreased to a certain degree the detecting accuracy of volcanic ash cloud. Therefore,it is necessary to introduce new data processing methods into the volcanic ash cloud remote sensing detection field. Principal component analysis(PCA)can compress a large number of complex information effectively into a few principal components; as a result,it is widely applied in the data compression and hyperspectral remote sensing field. Independent component analysis(ICA)is a recently developed new data processing method which can linearly decompose the observed data into mutually dependent components,and achieve the decorrelation and redundancy elimination of remote sensing data; so it has certain potential in volcanic ash cloud detection. A remote sensing detecting algorithm of volcanic ash cloud,which uses ICA method,is proposed after the exploration of the physics and chemical properties of volcanic ash cloud. This paper takes the MODIS remote sensing image of Iceland's Eyjafjallajokull volcanic ash cloud on April 19,2010 as data source. It uses ICA in volcanic ash cloud detection on the basis of the principal component analysis(PCA)processing of MODIS image,and gives comparison among these following parties: the detected results,the relevant research results, United States Geological Survey(USGS)standard spectral database and SO2 concentration distribution. The results show that: ICA can successfully obtain the information of the volcanic ash cloud from MODIS image; the detected volcanic ash cloud has a good consistency with the USGS standard spectral database and the SO2concentration distribution,thus,it can obtain pretty good detection results.