The Design Of Shadow Display Bitmap Technology And Its Implementation In GIS

In recent years, the application of geographical information system has been accelerated by the rapid development of economy in our country. The geographical information system has played the vital role in urban planning management, transportation, mapping, environmental protection, agriculture, charting, and so on. The geographical information system deals with each kind ofthe spatial data according to the geographic coordinate or the space position. It gains the satisfied information rapidly which the application needs, and expresses the processing result in the form of map, graph or data.In the development of geographical information system, the precise recognition of the screen graph is the technical problem which difficult to solve. In some practical applications, the approximate processing error has already surpassed the degree the people can accept. For example, when recognizing the graph elements, people can easily confuse the neighboring pipelines of water supply networks, thus the wrong pipeline information will be shown.Firstly, this article elaborated the graph recognition technique usually used and the excellence and disadvantage of it in the geographic information system, according to the reality application situation of geographic information system. In order to overcome the disadvantage of the commonly used graph recognition technique, the article proposed a new method -- the Shadow Display Bitmap technology. This technology is used to distinguish all kinds of simple and complex graph elements on screen precisely. This article discussed in detail the principle and the realization method of the Shadow Display Bitmap technology.In order to confirm the feasibility of the Shadow Display Bitmap technology in practical application, the article developed small geographic information system software in the application of water supply networks geographic information system using this technology. Experiments proved that this technology solved the recognition error problem of graph elements. This technology has the ability to recognize complex graph elements, and it is easy to realize compared to the commonly used graph recognition technique.