【摘要】：三維地理信息系統(tǒng)在現(xiàn)代社會中的應(yīng)用非常廣泛，而地形是3DGIS中的一個重要部分，作為空間中地物的載體和定位其它地物的依據(jù)，它的特點是數(shù)據(jù)量很大；從信息角度來看，網(wǎng)絡(luò)化在當(dāng)前世界各領(lǐng)域內(nèi)都呈現(xiàn)出一個重要趨勢，人們從網(wǎng)絡(luò)上獲取或分享信息，對于各領(lǐng)域的信息，數(shù)據(jù)的網(wǎng)絡(luò)需求越來越重，網(wǎng)絡(luò)帶寬的壓力也隨之提升；所以，海量三維地形數(shù)據(jù)和當(dāng)前有限的網(wǎng)絡(luò)帶寬之間必然存在著一定的矛盾，而此矛盾的解決也是國內(nèi)外研究的一個重要內(nèi)容。 為突破大數(shù)據(jù)量在有限帶寬上傳輸?shù)钠款i，一種合理的數(shù)據(jù)傳輸方法是本文的主要研究內(nèi)容。第一章的內(nèi)容是對此問題的提出，以及發(fā)展現(xiàn)狀、國內(nèi)外動態(tài)、研究內(nèi)容的介紹。從第二章開始在一些關(guān)于數(shù)據(jù)預(yù)處理的基礎(chǔ)知識上，分別對地形數(shù)據(jù)的存儲、組織、傳輸、緩存和實驗幾部分作詳細(xì)的研究分析。合理的數(shù)據(jù)傳輸方法是把視頻流傳輸?shù)乃枷�、技術(shù)結(jié)合在地形數(shù)據(jù)方面，因為它可以簡單的理解為邊下邊播，可以節(jié)省大量時間以及存儲空間；以及利用現(xiàn)代的硬件資源GPU快速提高圖形的計算處理、渲染等工作效率。 整體的處理方法先從對地形數(shù)據(jù)的分塊開始，結(jié)合小波變換的多分辨率的思想建立地形數(shù)據(jù)的多級模型表達(dá)，采取小波系數(shù)編碼壓縮方法把數(shù)據(jù)轉(zhuǎn)化成壓縮碼流形式，SPIHT具有較好的壓縮效果，也同時為流式傳輸數(shù)據(jù)提供了便利；針對流傳輸，在客戶端方面基于視點前提下，也提出了調(diào)度預(yù)取數(shù)據(jù)方法和傳輸規(guī)則；為了進(jìn)一步降低數(shù)據(jù)的吞吐量和帶寬的壓力，多級緩存策略被應(yīng)用其中，針對系統(tǒng)體系結(jié)構(gòu)，在兩端都設(shè)置緩存區(qū)，用戶端還分成顯卡緩存和內(nèi)存兩級，同時為了有效地利用內(nèi)存緩存空間，使用環(huán)形尋址辦法對內(nèi)存中數(shù)據(jù)進(jìn)行更新操作，，而緩存辦法應(yīng)用在服務(wù)器方面也是為了降低查詢次數(shù)，提升傳輸效率；最后就是針對此方法進(jìn)行實驗系統(tǒng)的設(shè)計與模擬，通過最后的結(jié)果來驗證方法是否可行。由于條件限制，使用局域網(wǎng)在客戶端與以高性能PC來作為服務(wù)器之間進(jìn)行數(shù)據(jù)傳輸實驗，借助流媒體的觀點，分析地形數(shù)據(jù)的特點，組織數(shù)據(jù)，減少冗余，提高壓縮效果，基于視點傳輸規(guī)則，借助多級緩存保證了最后成功的實現(xiàn)數(shù)據(jù)的實時傳送，在最后結(jié)論部分也分析了有很多的不足以及該方向還有許多的內(nèi)容有待更深入的思考研究。
[Abstract]:3D GIS is widely used in modern society, and terrain is an important part of 3DGIS. As the carrier of space and the basis of locating other features, it is characterized by a large amount of data. From the point of view of information, network is showing an important trend in every field of the current world. People obtain or share information from the network, and the network demand for information in various fields becomes more and more serious. The pressure of network bandwidth also increases; Therefore, there must be a certain contradiction between the massive 3D terrain data and the current limited network bandwidth, and the solution of this contradiction is also an important content of domestic and foreign research. In order to break through the bottleneck of large amount of data transmission on the limited bandwidth, a reasonable data transmission method is the main research content of this paper. The first chapter is the introduction of this problem, the present situation, the domestic and foreign trends, and the contents of the research. In the second chapter, on the basis of some basic knowledge about data preprocessing, the storage, organization, transmission, cache and experiment of topographic data are studied and analyzed in detail. The reasonable method of data transmission is to combine the idea of video stream transmission with the technology of terrain data, because it can be understood simply as "side down" broadcasting, can save a lot of time and storage space; And the use of modern hardware resources GPU to quickly improve the graphics processing, rendering and other work efficiency. The whole processing method begins with dividing the terrain data into blocks, combining the idea of multi-resolution of wavelet transform to establish the multi-level model expression of terrain data, and adopting the wavelet coefficient coding compression method to transform the data into compressed code stream form. SPIHT has good compression effect, and it also provides convenience for streaming data transmission. On the premise of client-side view, scheduling prefetching method and transmission rules are also proposed for streaming. In order to further reduce the pressure of data throughput and bandwidth, the multi-level cache strategy is applied, aiming at the system architecture, the buffer area is set at both ends, and the client is divided into two levels: video card cache and memory. At the same time, in order to use the memory cache space effectively, the circular addressing method is used to update the data in memory, and the cache method is used in the server to reduce the number of queries and improve the transmission efficiency. Finally, the design and simulation of the experimental system are carried out, and the feasibility of the method is verified by the final results. Because of the limitation of the condition, the LAN is used to carry on the data transmission experiment between the client and the high performance PC as the server. With the help of the view of streaming media, the characteristics of the terrain data are analyzed, the data is organized, the redundancy is reduced, and the compression effect is improved. Based on the view transmission rules, the multilevel cache is used to ensure the successful real-time data transmission. In the final conclusion part, there are many shortcomings and there are still a lot of contents to be further studied.
【學(xué)位授予單位】：蘭州交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2013
【分類號】：P208

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