A Study Of Data Transmission Strategy In Geographical Information Services

The radical difference between Geographical Information Services and Geographical information systems is that it emphasizes the coherence of sharing services and individuation services. Geographical Information Services is, in the transmission process of spatial information, to provide high-quality, meeting-demand spatial information to different clients. Therefore, Geographical Information Services studies on the process during which those different results were produced, and the mode to put these processed into practice. This paper lucubrated on some questions in building and realizing Geographical Information Services. Main research contents and innovation as foliowings:1. The author analyzed present two advanced Geographical Information Services modes, GIS based on Web Service and Grid GIS, and summarized their technology characters, key technologies and various technology shortcomings. After that, referring to those frameworks, the author built up a Security Based Geographical Information Services System Framework. Comparing with those two modes, new system framework has the characteristic of structure more flexible (mixed mode service system, which can satisfy multiple demands), resource data's accessing and network transmission more safe, service right management more convenient.2. From the data transmission and application in Geographical Information Services, after analyzing every transmission protocol's characteristic, the author studied the Geographical Information Service's particularity on transmission layer and application layer of network data transmission protocols, and prompted corresponding data transmission strategy according to particular demand. Thus different kinds of data transmission capabilities in application system and the integrate ability to offer map service, location service and various application services to multiple clients were improved.3. Considering the application specialty of spatial image data, the author analyzed the character of lifting wavelet analyze algorithm and JPEG2000 image compression technology, built up a compression and transmission model for spatial image data based on lifting wavelet transforming and JPEG2000 image compression technology, and realized the technology of gradual data transmission of layered compression, layered transmission, layered visualization, thus improved the response efficiency and reduced the gross of network data.4. Combining with practical demand, the author analyzed common data encrypting algorithms. Based on image data compression and transmission model in Geographical Information System, the author integrated general encrypting technology, built up a secure-based spatial image data compression and transmission model, which solve the conflict between safety and efficiency in data transmission and application.5. The author analyzed the technology characters of vector data common algorithms, and the characters of vector data's organization and storage. Then according to the characters of wavelet transforming, the author built up a linear elements compression and optimize self-adjusting model based on wavelet transforming, Douglas algorithm and curvature analyzing algorithm.6. Considering general lossless compression technology to file, and according to storage character of spatial vector data, the author built up a high-efficiency lossless compression model based on integer transforming, two-rank difference transforming, two-rank average transforming and LZW lossless compression algorithms.7. By analyzing the characters of gradual transmission models home and abroad, according to the characters of vector data storage and visualizing and spatial information cognize principles, which is from coarse to details, from collectivity to local, the author built up a spatial vector data's gradual transmission model based on wavelet transforming, thus reduced the response time to clients' requirement. Meanwhile, multi-scale spatial vector data could be sent to clients at the precondition of no data quantity increasing.8. Based on the research contents just mentioned, according to client's particular demand and application environments, the author built a secure-based Geographical Information Services system archetype.