Research And Application Of WebGIS Based On Public Map Service Model

Geographic Information System (GIS) is a technology system, which can collect, store, manage, manipulate, analyze, display and describe geographic data distributed in overall Earth's surface, regional area and localization, in support of computer hardware and software. The objects manipulated by GIS are geospatial data entities and relationship, including space positioning data, graphics data, remote sensing image data, attribute data. GIS is used to analyze and treat various phenomena and processes occurred in a certain geographical area, and solve complex planning, decision-making and management issues.GIS is composed of many technologies and knowledge. In recent years, Web-based geographic information system, which is always named WebGIS, has being a hotspot with the development of theories and technologies and changes in demand. However, as a new form of GIS, WebGIS both in theory work, and in the application are still in the development stage. And now, most of WebGIS platforms have limited space analysis capabilities and no optimization for Web application. Meanwhile, many WebGIS platforms have no capability in certain field, such as agricultural applications. There are other problems. The prices of these products are too expensive, inefficient, usually contain lots of coding, can not be cut down, and possess their own copyright. As s result, this paper constructs a WebGIS platform, named PMGIS, based on new Web application technologies and models.The architecture of PMGIS in this paper has three levels: application tier, Web tier and service tier. We use Server API method to construct PMGIS. The mode of PMGIS is Public Map Service Model which uses Ajax technology to manipulate data in the browser and display tile maps. PMGIS provides many basic service interfaces instead of components to make efficient. And it has an open framework used to make development flexible and easy. PMGIS uses the data model and data exchange format published by OpenGIS for opening.This paper expounds the principle and realization of Public Map Service Model. Its core is Tile and Ajax. Ajax technology can control maps in the browser by JavaScript, such as panning, zooming and layer-controlling. This technology makes systems have more functions, no need to plug-ins either. Meanwhile, JavaScript is support by most of browsers. The principle of Tile technology is displaying tile maps in clients and responding to user's requests in the way of image-linking by the pre-build technology. In this case, there is no need to send requests to the server for simple operations. Also, there is less data transmitting in the network.PMGIS, designed like that, have some superiority. It can work efficiently on Win32 platform and Linux platform. It has not much code. Also PMGIS provides targeted services and convenient development.Digital agriculture is the advanced stage that information technology applying in agriculture. Agricultural information process, intelligence process, precision process, and digital process will be the result of information technology applying in agriculture. It must promote agricultural information process greatly. It can be reasonable to use agricultural resources, to raise the quality and the output of crops, to reduce production cost, and to improve ecological environment and agricultural sustainable development. In digital agriculture, all data spread based on geography, therefore, GIS technology is the key technology of the digital agriculture.This paper constructs a digital agriculture spatio-temporal information management platform based on our PMGIS. It is a part of the project named "digital agriculture spatio-temporal information management platform" which is took part in by the Key Laboratory of Symbolic Computing and Knowledge Engineering of Ministry of Education. Its purpose is to construct the system which can manage the agriculture information uniformly and canonically by using some software and techniques, such as GIS platform, expert system, spatio-temporal reasoning, data-mining and so on. The platform contains three parts: the management of agriculture information, the analysis of agriculture information and the expert system of agriculture. GML is a criterion based on XML. It's published by OpenGIS. Because GML is an open standard, it affords perfect resolve methods for sharing geography information. Firstly, this paper uses GML as the criterion for agriculture spatio-temporal information, and analyzes its structure, geometry data model and its supporting for tense information. Secondly, we design the spatio-temporal database which is the base of our platform. Thirdly, we realize the function of analyzing spatio-temporal information based on PWGIS. It contains buffer analysis, theme map, spatio-temporal query, space orientation and so on. We also describe the important theory and algorithms of spatio-temporal reasoning. At last, we add the expert system of agriculture knowledge to our platform to make our platform have the ability of intelligent reasoning and decision-making.The digital agriculture spatio-temporal information management platform can afford some methods which can be used for building farmland geography information system, managing farmlands, planting crop and inspecting. The application system, based on it, can control the amount of the seeds and the pesticide which are used in every piece of farmland accurately. It also can improve the yield of the crop. At the same time, it can control the process of producing and reduce cost. As a result, it can guarantee the full use of the agriculture resource. At last, the paper designs an intelligent fertilization system based on the digital agriculture spatio-temporal information management platform. It uses the platform in the agriculture applications, and shows the platform's actual results.