浅析基于IWT和FCM的曲线矢量数据压缩方法.docx

浅析基于IWT和FCM的曲线矢量数据压缩方法
 
 
　摘 要:矢量数据压缩对于GIS数据的存储、网络传输以及在移动设备中的使用都具有重要意义。在此通过对曲线矢量数据特点的分析,提出基于整数小波变换的矢量数据压缩方法。压缩方案包括3个主要流程:矢量数据整型化。曲线矢量数据具有相邻坐标点间坐标值大小差别不大的特点,将坐标点间的差值转换为整型的偏移量,用偏移量表示矢量数据的坐标点,利用整数小波变换处理偏移量序列。实验表明,偏移量序列经过整数小波变换得到的小波系数序列在空间分布上更加集中,适合使用高效的编码压缩方法;对变换后的小波系数进行编码压缩。在此使用模糊C均值聚类字典法编码实现了曲线矢量数据的有损编码。通过实验和其他压缩算法结果的对比,该方法具有压缩比较高,失真小的特点。关键词:空间矢量数据; 整数小波变换; 模糊C均值聚类; 字典法编码; SHP
　　　　
　　Method of Curve Vector Data Compression Based on IWT and FCM
　　ZHANG Jun-lan1, WANG Yi2
　　(1. College of Information Science and Technology, BEijing Normal University, Beijing 100875, China;
　　2. Ocean University of China, Qingdao 266003, China)
　　Abstract: The vector data compression has great significance in GIS data storage, network transmission and its application in mobile devices. A compression method based on the integer wavelet transform (IWT) and fuzzy C means (FCM) is proposed according to the analysis for the characteristic of curve vector data. The compressionscheme includes 3 steps: integer form of vector data, offset sequence processing with IWT and coding compression of transformed wavelet coefficients. The lossy coding of curve vector data was realized with the dictionary coding of FCM. Compared with other algorithms, this method has the characteristics of high compression ratio and less dist
: spatial vector data; integer wavelet transform (IWT); FCM;