摘要
本文简要介绍了星载微波合成孔径雷达(SAR)传感器的特点及其图像数据存储技术,遥感图像数据库管理系统的国内外现状,以及Web-GIS技术的基本概念和发展动态。借鉴美国UND开发的针对Landsat图像的DNGP平台,利用开源软件设计并实现了基于Web-GIS的SAR图像数据库系统。
系统构架采用三层的B/S模式,分为用户服务层、业务逻辑层和数据库服务层。其中,用户服务层是客户端,业务逻辑层和数据库服务层是服务器端。系统的特点是胖服务器端/瘦客户端。服务器端完成SAR图像数据管理、用户管理、辅助信息和管理子系统等功能,其中,SAR图像数据管理包括图像预处理、图像检索及图像浏览、订购和下载等;用户管理包括用户注册、修改用户信息及用户登录等;辅助信息包括帮助信息、相关网站链接和新闻等。客户端仅完成对用户的请求处理及结果的显示。
系统平台全部采用开源软件构架,操作系统为Linux--Fedora Core 10。用户服务层采用HTML、CSS以及Ajax等技术。业务逻辑层由地图服务器和Web服务器组成,采用UMN Mapserver为核心辅以GDAL、Proj和Freetype等开源组件作为地图服务器;采用Apache作为Web服务器。数据库服务层采用PostgreSQL及其空间数据库组件PostGIS作为数据库服务软件。PostGIS能够处理空间地理信息的相关操作,为SAR数据的存储和来自业务逻辑层的相关请求提供有力的支持。本系统采用开源软件都遵循Open GIS Consortium(OGC)协议,为系统的通信和今后的扩展升级提供了便利。
本文针对海洋遥感教育部重点实验室的研究需求,考虑了多源SAR图像数据的存储和管理。由于各种SAR传感器的数据格式都不相同,给数据存储及管理带来不便。为了解决这一问题,把各种格式的SAR图像数据转换成GeoTIFF图像格式。图像转换的同时,完成了SAR图像的几何校正。目前国际上的以SAR数据产品浏览和订购为主要目标的SAR数据管理和服务平台一般不针对多源SAR数据。本文完成的基于Web-GIS的SAR图像数据库系统ORSISAR已在海洋遥感教育部重点实验室试运行。
This paper briefly introduced to the characters of the satellite microwave Synthetic Aperture Radar (SAR) and its image storage technology, the domestic and foreign situation of remote sensing images storage in these days, and the basic conception and the last development trends of Web-GIS. Using for reference to the Landsat image distribution system– DNGP developed by UND, Taking advantage of open source software, a Web-GIS based SAR image database system is designed and completed.
Based on the three tier Browser/Server (B/S) architecture model, the system is consisted by three function logic tiers: user service tier, business logic tier, and database service tier. The user service tier is client side and the business logic and database service tiers are server side. The characteristic of the system is fat server and thin client side. The server side has the functions of SAR image management, user management, assistant information, and management sub-system. SAR image management includes image preprocessing, image searching, display and download. User management includes user registration, user information modification, and user logging in. Assistant information includes help information, interrelated website link and news. The client side just has the functions of user request processing and results display.
The system platform is all built by open source software. Operation system is Linux-Fedora Core 10. Client service tier used HTML, CSS, Javascript ,and Ajax, etc. The business logic tier is consisted of map server and web server, in which map server software is UMN Mapserver combining with GDAL, Proj, and FreeType, and the web server software is Apache. The database service tier is managed by PostgreSQL/PostGIS. PostGIS is a spatial extension of PostgreSQL to enable the geographic objects support, which provides the support for the SAR image storage and requests from business logic tier. All the open source software is in the restriction of Open GIS Consortium (OGC), which provides convenience for the data transaction and extension of the system.
To meet the research requirement of the National Laboratory for Ocean Remote Sensing of MOE, the storage and management of multiple SAR image data are considered. Different SAR sensor has different data format, which give the inconvenience to the data storage and management. In order to solve this problem, different SAR image is converted into GeoTIFF format, and the image Geometric correction is finished at the same time. Nowadays, almost all of the service systems, around the world, for SAR data management targeting to the SAR data display and ordering don’t provide multiple SAR data service. The Web-GIS based SAR database system– ORSI SAR presented by this thesis is running in the National Laboratory for Ocean Remote Sensing of MOE for test.
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