Research And Implementation Of Network Geographic Information System

WebGis is a computer information system, which can store, manipulate, analyze, display and use geographic information in network environment. This thesis focuses on how to issue electric maps through Internet, which means that the users can manipulate the map interactively in browser/server pattern without installing any GIS software in the browser side.There are two main application fields of WebGis: Internet and Intranet. The main application on internet is map info issuing, browsing and searching;the main application on intranet is map info issuing between departments. Undoubtedly, WebGis is the prototype of "digitalearth" or "digital city" .Based on GIS and network frame, the thesis brings up the WebGis service frame, describes the whole process of map issuing and bus interchanging from demand analysis to implementation in detail. The main content of the thesis includes:Firstly, By analyzing the map data transfer technique of WebGis, and considering that map data is of large amount but low transferring speed, the thesis presents data organization method and spatial index mechanism, and so improves the network transferring speed of map data.Secondly, The dynamic annotation of spatial data is important to the showing of electronic map, whose appearance and rationality affect electronic map' s showing very much. In addition, the algorithm should not be too complex, so as to show the map annotation in real time. In this paper, a new method for dynamic annotation algorithm is provided based on the theory of raster, it simply divides the screen first, and then takes point, line and plane into consideration.This annotation configuration is reasonable, results in no overlap.Furthermore, the thesis constructs the public traffic network modelto solve the problem of bus interchange, and based on the model, the thesis puts forward the solution of bus network' s shortest path problem based on improved dijkstra algorithm.The design emphasizes the optimizing and upgrading performance as well as ensuring the system stabilization. The preprocessing and pre-download of map data, the dynamic annotation algorithm of spatial data, and the data modeling and shortest path algorithm in bus interchange gets good result in practical application.