ESTABLISHING THE ENGINEERING SEISMOLOGY WebGIS APPLICATION SYSTEM BY USING GIS SOFTWARE COMPONENT

An engineering seismological WebGIS application system (ESWebGIS) is established in this paper by using GIS software Component MO/MOIMS. The system implements the sharing of spatial data and GIS applications and greatly promotes the percentage of utilization of spatial information and GIS applications for engineering seismological studies. Users can easily browse, search, analyse and use the engineering seismological spatial information from Internet just like on their local computers, and they can also download the needed data to their local machines for use in their locally installed GIS software. The ESWebGIS system adopts the popular three layer Browser/Server architecture and thin client/fat server model. Development tools, spatial database and WebGIS applications are all installed and running on a remote map server. All client requests are submitted to the map server for processing, no need to download or install the GIS components on client computers. This model is very convenient for users to use. The GIS components MO/MOIMS, JavaScript, VB6.0, HTML and Oracle8i etc. are used to develop the ESWebGIS. The program modules of ESWebGIS are divided into basic GIS function modules and engineering seismology application modules. The basic GIS function modules, such as map's zoom out, zoom in, pan, overlay, point query, layer moving, active layer locating and labeling are programmed by using MO/VB. These modules are commonly needed for any GIS application system and not limited to a specific database or project. They can be freely called by any GIS application. Engineering seismology application modules, which serve the engineering seismology studies, are designed and coded according to the GIS database constructed for engineering seismology. The spatial data that can be shared through ESWebGIS system have been collected and input into GIS database. The commercial GIS software MapInfo5.0 is used for the database's construction.To improve the system's performance, some effective measures, such as detailed delamination of spatial objects, reasonable organization and logic classification of database, multilevel display scales, and data partition index based on grid have been taken to increase the transmission and display speed of maps on Internet. These improvements make it possible that a great number of map layers with different scales are quickly displayed, overlayed and dynamically integrated on Internet. The running results of ESWebGIS indicate that these measures are effective. In addition, a method called agent index preprocess is used to achieve the interoperability between GIS data with different formats coming from different remote database servers. The ESWebGIS realizes the upgrading of GIS to networking environment, and it can be used to fulfill the following tasks: (1) To browse, draw and manage maps on Internet; (2) To perform attribute query and spatial query of maps; (3) To perform spatial analysis and statistical analysis; (4) To upload and download spatial data files onto/from GIS map server; (5) To publish any GIS data by using Common map browser; (6) To remotely update the spatial data of GIS database on GIS map server; (7) To manage the users and to make the system secure. The ESWebGIS is really an interactive On line GIS system, which is open to global Internet users, and is not limited to certain region. It will greatly enhance the sharing and using efficiency of spatial data.