面向流媒体传输的空间数据变化累积模型

将流媒体技术引入到以矢量数据为主的网络GIS传输中,其关键是建立逐级精细化的多层次表达模型,并在服务器端数据预组织上建立线性索引结构。本研究针对该目标建立一种矢量数据多重表达的新模型,即变化累积模型,认为尺度空间中从粗到细的数据表达过程是一些"变化"的累积,"变化"表现为两个连续尺度表达间的差别,通过"变化"元素的逐渐增加或减少来实现渐进传输。基于该模型对面状数据渐进式传输进行研究,将多边形分级剖分为一系列凸壳或外接矩形的基础上建立变化累积模型,通过剖分元素的组合完成渐进式流媒体传输。

Research on GPS Pre-processing Method for Ionosphere-free Combination Data Using Wavelet

In order to improve position precision of PPP, a pre-processing method is proposed. The method is that correcting GPS raw data using de-noised residual data of GPS combination observations, which is the output of wavelet analysis of pre-adjusted residual data. In this paper the principle and flow of the pre-processing method are introduced in detail. Then an experiment was showed, in which inner precision and system accuracy were compared between using and without using this pre-processing method, and compared between different wavelet analysis strategies. The result shows that this method can improve position precision efficiently when the GPS data are contaminated by un-modeled system error.