LASIS' Hyperspectral Interference Imagy Compression Methods Research

Hyperspectral imagery is generated by collecting spatial information as well as the spectral information of the earth targets, and describes the targets with more detail, so it has great value of applications in agriculture, geology, ocean and military surveillance. With the increasing of remote sensor resolution, we get massively large image data sets which it is difficult to access and transport. Therefore they must be compressed before being processed, storage and transmission. As a kind of three-dimensional data sets, it is different from the 2D still image, and is also different from video series, so the general image compression method is not efficient for them. Analyzing their character and study appropriate algorithm for coding is very necessary.We particularly analyze the character of the Large Aperture Static Imaging Spectrometer (LASIS) hyperspectral interference images and give the inclusions. LASIS images not only have the spatial correlation, which is the same as general 2D still images, but also have the inter-frame correlation and inter-band correlation. LASIS image is amplitude modulated by the interference spectrum. The spectral information concentrates about the zero optical path difference, and needs to be efficiently protected. This character is very important, which makes it difficult to process. The followed compression algorithms specially designed according to LASIS's character have good performance.In order to meet the demands of high real-time, low complexity and low memory, we proposed a Modified Listless SPIHT algorithm, which uses 2-bit state-flag per coefficient, instead of the three variable-length lists of SPIHT. The MLSPIHT save much memory and complicated list-operating required by the original SPIHT, and need less memory and operation than the LZC.Considering the characteristic quality of LASIS, we proposed the following scheme: (1) 3D asymmetrical DWT with equal length tree and 3D-MLSPIHT based on Band Of Interest. The scheme defines the whole LASIS sequences as a coding unit and take fully consideration of LASIS's inter-band correlation. It get good performance under the given compression rate. (2) 3D-MLSPIHT algorithm based on Region Of Interest. This method define every 8 sequential images as a coding unit, and satisfies the requirement of less memory and lower operation complexity. (3) Nearly 3D-MLSPIHT algorithm based on Region Of Interest. This algorithm defines tow contiguous images as a coding units to decrease more memory and operation complexity. Its compression performance is between the 2D-SPIHT and 3D-SPIHT. This scheme is specially designed under the condition of the highest real-time and the lowest memory. All the algorithms have the PSNR of above 40dB at the 8:1 rate and efficiently protect the interference spectral information as well. They all meet the application requirement of the LASIS system.This paper is based on the analysis of the LASIS image characters, especially on its spectral character. According to different application requirements, we propose different schemes, and gives the numerical experimental results and conclusions.