Integrating GPS Data within Embedded Internet GIS
Arunas STOCKUS Alain BOUJU Frédéric BERTRAND Patrice BOURSIER
University of L a Rochelle - L3i
Avenue Marillac
17042 La Rochelle - FRANCE
Tel. +33 (0)5 46 45 82 62
{arunas.stockus, …}@univ-lr.fr
1. INTRODUCTION
An embedded geographic information system (GIS) is a specialized system that could mostly be considered as a mobile navigation system. Its typical characteristics concern the presentation of geographical information to the driver, positioning and guidance. However, due to their reduced computational power and their autonomy, many actual navigation systems have some limitations. The geographical information they can use covers only limited areas, and its precision may be insufficient in some situations. The autonomy of the system complicates data updates and access to distant information sources, especially those providing dynamic information.
But the actual development of technologies changes the way information can be accessed and processed. It minimizes the differences between desktop applications and embedded ones by bringing the power of desktop computational technologies into mobile devices. It gives the possibility to use the same kind of applications and data access modes with both kinds of environments: presentation of multimedia information, connection to the Internet, etc.
In this paper we present an embedded GIS, which is based on such technologies. Its architecture is a client-server one, and the system components may give access in real time to distant information servers. We use a satellite based localization system(GPS) for the geographical positioning of a mobile unit (e.g. avehicle). The connection to distant data servers at the physical level is based on the use of a cellular phone. At the software level, we use an Internet connection for exchanging data between the components of the system. Information integration, visualization and processing is made possible by using a Java enabled Web browser and a Java applet.
在嵌入式Internet GIS中的GPS數(shù)據(jù)整合
1. 緒論
嵌入式地理信息系統(tǒng)（GIS）通常被認(rèn)為是移動導(dǎo)航系統(tǒng)。它的典型特征是給駕駛員提供地理信息顯示、定位和導(dǎo)航功能。但現(xiàn)有的導(dǎo)航系統(tǒng)都有一定的局限性，主要表現(xiàn)在計算能力和自動性不足上。這些導(dǎo)航系統(tǒng)只提供了有限區(qū)域內(nèi)的地理信息，而且這些地理信息的精度不能滿足有些情況要求。系統(tǒng)的自我管理使數(shù)據(jù)更新和對遠(yuǎn)方數(shù)據(jù)特別是動態(tài)數(shù)據(jù)的訪問，變得更加復(fù)雜。移動系統(tǒng)和數(shù)據(jù)服務(wù)器通訊時用到的特殊技術(shù)要求安裝特殊的裝置，這限制了它的應(yīng)用。
但實際技術(shù)的發(fā)展改變了數(shù)據(jù)的訪問和處理方式。它通過賦予移動設(shè)備和臺式機類似的計算能力，縮小了臺式機和嵌入式的應(yīng)用軟件的差別。使得在兩種環(huán)境中運用相同的應(yīng)用軟件和數(shù)據(jù)訪問模式成為可能，如，多媒體信息顯示，Internet連接等。
在這篇文章中，我們介紹一個用上述技術(shù)實現(xiàn)的一個嵌入式GIS。它是客戶機—服務(wù)器模式的，且系統(tǒng)各成員可以實時訪問遠(yuǎn)程信息服務(wù)器。我們通過衛(wèi)星定位系統(tǒng)（GPS）來得到移動終端（如，車輛）地理信息。在物理方面，移動終端和異地數(shù)據(jù)服務(wù)器的連接是通過手機來實現(xiàn)的，在軟件層次上利用Internet連接，來實現(xiàn)系統(tǒng)不同成員間數(shù)據(jù)的交換。通過一個Java網(wǎng)絡(luò)瀏覽器和Java程序可實現(xiàn)信息的綜合，可視化和處理。
在我們系統(tǒng)構(gòu)成中還有一個嵌入式本地服務(wù)器。它的主要目的是保證在最佳時間實時訪問其他數(shù)據(jù)源：（i）本地的，如GPS設(shè)備發(fā)送的數(shù)據(jù)，和（ii）異地的，如在異地服務(wù)器上的空間數(shù)據(jù)數(shù)據(jù)庫中的數(shù)據(jù)。
在下面的章節(jié)中，我們將介紹我們工作的框架，即對嵌入式GIS的要求和可能的技術(shù)處理方法。我們還將介紹我們的選擇和由此導(dǎo)致的問題：訪問和綜合不同數(shù)據(jù)源的數(shù)據(jù)，尤其是GPS設(shè)備提供的。接著我們比較不同的解決方式，得出我們的選擇。