用离散小波变换对格网DEM数据压缩中的关键技术

DEM数据具有不稳定、相关性差的特点,用离散小波变换对格网DEM数据进行压缩处理时,其边界问题将更为突出,主要表现在边界失真非常严重.这种现象不可避免地导致重建DEM数据精度的损失严重.为了最大限度地减弱边界问题的影响、提高压缩比,在进行格网DEM数据压缩时,作者将二维离散小波变换的边界问题转换为一维离散小波变换的边界问题,大大减小了边界失真区域,提高了重建DEM数据的精度.进而,用相应的算法进行了DEM压缩实验, 结果表明:可获取高压缩比且高精度的重建DEM数据.

Key Technique in Compressing Grid DEM Data with Discrete Wavelet Transform

Due to the instability and less relativity of DEM data,the boundary problem in discrete wavelet transform becomes more outstanding and kittle when compressing grid DEM data with DWT,which mainly indicates the distortion degree appears very severe.This phenomenon will inevitably lead to serious loss of the precision of reconstructed DEM data.In order to utmost weaken the influence of boundary problem and improve the compression ratio,the boundary problem of two-dimensional DWT was transformed into the boundary problem of one-dimensional DWT,which can enormously diminish the area of boundary distortion and greatly improve the precision of the reconstructed DEM data,then the corresponding algorithm was proposed.Moreover,according to the algorithm,some experiments were made.The results prove that not only higher compression ratios but also reconstructed DEM data with high precision are achieved.