动态GIS数据对象模型探讨

Research on TGIS Data Object Modeling

动态地理信息系统(Spatial-Temporal Geographical Information System)是GIS的必然发展趋势,是实现动态数字地球的关键技术。静态3D GIS的技术已经成熟,而将时间维加上后形成4D的TGIS还处于数据模型研究阶段,主要原因是超海量数据的存取和查询问题仍然没有完全解决。在对已存在的数据模型进行探讨并在此基础上进行深度综合研究,提出了新的观点:结合快照模型的简单易行性和面向对象模型的方便灵活性,同时避开快照模型的不一致性和冗余性,以及面向对象的复杂性,形成复合的基于快照方式的面向对象模型。它将是一种实用的TGIS数据模型,在对时间属性的处理方面采用独到的方法:首先按照时间片进行分层,建立一个基数据,然后通过快照方式产生缓冲数据,经过比较形成一个以对象变化为主的带有时间戳的新数据层,最后再通过其变化函数将离散的时间层连接起来,形成一个有机连续的数据库。这样,在数据存储方面,节省了很多空间;在查询分析方面,使以对象变化分层的数据算法更容易实现,同时可以实现对象的历史回放功能。此理论方法有效地对TGIS难点进行大胆探讨并通过自动元胞机理论(CA)予以证明。

Spatial-Temporal GIS is inevitable tendency to realize dynamic digital earth with the essential technology. The technology of static 3D GIS is already well developed, but the 4D GIS, traditional GIS plus temporal dimension is still under the stage of theory study because its essential technology involves creation and manipulation of the temporal data base, which are related to temporal data base modeling, mainly dealing with storage and research of mass data. In this paper, it is a reasonable TGIS data modeling to combine simple and feasible snap-short modeling and convenience with flexible object-oriented data modeling, while avoiding the consistent and redundant snap-short modeling and complex object-oriented data modeling. The paper adopts a special way in dealing with the property of time： first step is to create a fundamental data, then produce buffer data through snapshot data modeling, thirdly form a new data pool with time stab, thus plenty of space is saved in data storage with this process and it is easier to realize calculation of data, which is to divide store layers based on the varying objects, finally connect discrete layers to continuous with changing functions. Meanwhile, it can be once more for history events. The theoretical approach creative study the difficulties of TGIS and has been substantiated through Automatic Cellar Theory.