基于云计算的分布式切图服务设计与实现

The Design and Implementation of Distributed Map Tiling Service Based on Cloud Computing

云计算如何在GIS领域真正落地,传统GIS技术如何改变才能适应形势,并真正将云计算和云平台的优势为自己所用,是当前云GIS最重要的研究课题。传统GIS地图服务中,地图缓存是基于单机预先切好的地图瓦片,并通过单机对外提供。这种传统的切图技术,对计算资源的利用率较低,且海量数据切图时间长达数月甚至数年,严重影响工作效率,加之没有故障恢复机制,切图任务一旦出现故障,整个切图工作都要推倒重来。在云计算快速发展的形势下,如何利用云平台的优势,提升海量地图数据的切图效率和稳定性,就成为云GIS迫切需要解决的问题。本文在分析云计算技术优势的基础上,对传统切图技术进行了改进,提出了分布式切图服务的设计思路,实现了地图瓦片的分布式生成、管理与发布,对比测试证明,分布式切图的性能、稳定性较传统方式有明显提升。基于此种设计实现的SuperMap iServer Java 6R(2012)分布式切图模块,支持地图瓦片的分布式切片和分布式存储管理,支持多种分布式文件系统、NAS与大数据存储系统(如FastDFS、EMC Isilon等),进一步提升了地图瓦片的存取速度和支持的并发数。本文提出的分布式切图技术,是对传统地图缓存方式的创新,为云GIS提供了一定的研究基础。

It has been the most important research topic of Cloud GIS that how the Cloud Computing technology is used in GIS and how the traditional GIS changes to use the Cloud Computing technology advantages .In the traditional GIS map service , the map cache is matrix of map tiles that is tiled and provided by a single computer .This map tiling technology has the low computing resource utiliza-tion and a very high cost of time , which could affect working efficiency seriously .Furthermore, once the map tiling process encounters a problem, the whole work has to be restarted , because there is no recovery mechanism on this single computer .With the rapid devel-opment of Cloud Computing , it has been an urgent problem that how Cloud GIS can improve the efficiency and stability of macro maps tiling.This paper puts forward a strategy of distributed map tiling service , which is an improvement of the traditional map tiling tech-nology on single computer and is based on the analysis of Cloud Computing .With this strategy , map tiles can be tiled , managed and published as distributed map tiling service .According to the contrast test , the performance and stability of distributed map tiling has been promoted significantly as to the traditional method .The distributed map tiling module of SuperMap iServer Java 6R(2012 ) has been built based on this design , with which the macro map can be tiled and storaged in distributed way .Also, multiple distributed file systems, NAS and large data storage systems (such as FastDFS, EMC Isilon etc.) can be used to improve the speed of map tile ac-cess and achieve high concurrency .The distributed map tiling technique proposed by this paper is an innovation of the traditional map tiling method.Also, the distributed map tiling technique provides the research foundation for the Cloud GIS .