Study On Early Warning Of Geohazards Based On3D WebGIS Technology

Early warning of geohazard ascts as one of the main contents of hazard riskassessment and management, in addition to its important role in improving theactively responding ability of human beings to control and mitigate geohazards. Withthe rapid economic growth, human beings keep expanding their living space tomountain areas. Geohazards, resultantly, occur more and more frequently in recentyears than ever before, causing catastrophic economic losses and fatalities. TheSouthwest of China is one of the most affected regions by such events, where thecomplicated geological condition exists and gestates earthquakes (e.g., the5.12Wenchuan Earthquake). Geohazards such as debris flow and landslides keep beingbrought to reality with complicated development and failure mechanism. Informationfor disaster prevention and mitigation has been largely promoted by3D visualizationtechnology of WebGIS and real-time transmission of monitoring data. Research intoearly warning of geohazard with3D WebGIS technology, therefore, appears to be ofgreat significance, both theoretical and practical, for mitigating geological disaster. Inthe present research, reasonable analysis, interpretation and discussion have beencarried out in this dependency, and major outcomes are given as follows:(1) An integrated methodology for geohazard automatic monitoring and warningsystem has been established.Early warning of geohazards takes monitoring as the main approach, and thereal-time monitoring data as the fundamental for stability analysis of geohazardfeatures, and aims to improve the active response of human beings to geohazards. Forachieving a robust geohazard early monitoring system, the workflow below is putforward, methods of early warningâ†'database establishmentâ†'3D display platformâ†'remote monitoring data transmission networkâ†'early warning system. The PhDstudy is progressed by following this workflow and efforts are put on the keytechnologies, developing the relevant program and system in order to realize earlywarning of geological disaster.(2) Based on analyzing the pre-processing method for data from single/multiplemonitoring points, and the historical data of southwest China, a warning criteria system is established for landslides. An integrated methodology for early warningmodel of geohazards has then been established according to the fuzzy mathematicalprinciples with selection of main criterions as indexes of comprehensive warning.(3) The management and display platform for geohazard information has beendeveloped based on3D WebGIS technology, which contains kinds of spatial andattribute data and provides fuctions, real3D roaming for example.â‘ An approach to fast building3D image by taking OpenGL interface and highresolution aerial photo as texture data has been proposed, which makes the foundationof integration of huge number of remote-sensing images and topography data.â‘¡Large volume spatial data have been visibly managed by data compression,tile-pyramid and quadtree retrieval. Velocity of displaying huge number of spatial datahas been accelerated by surface culling in the view frustum together with dynamiccreation of Level of Detail (LOD).â‘¢Spatial data transmission has been improved by distributed storage systemand the revised load-balancing algorithm of server cluster (weighted least-connectionscheduling). Finally, Sharing of spatial data has been realized by RepresentationalState Transfer (REST) service.â‘£Multi-source database is built according to the following process, datacollectionâ†'data sources analysisâ†'landslide type selectionâ†'landslideparameters slectionâ†'hardware and softwareâ†'database generation.⑤A static structure of geohazard data is designed using the Unified ModelingLanguage (UML) to establish the forms, methods, restrictions and relationships. Inaddition, the muti-dimentional geohazard model has been discussed and ExtactTransform and Load (ETL) tool has been used to design the data warehouse forgeohazard by means of subject-oriented analysis method.(5) An automatic monitoring network for geohazards composed of WirelessSensor Network (WSN), data remote transmission and monitoring center, has beenestablished based on Internet of Things technology.â‘ Based on wireless communication protocol, a local network containingself-organization and changeable features has been established, which is connected toremote network by sink node.â‘¡GPRS/CDMA compares favorably with Beidou satellite system in terms ofefficiency, simplicity and expenses, while its usage is restricted by base station. Onthe contrary, Beidou satellite system has no regional restriction, but is limited by data capacity and interval. Geological remote network is finally designed into amuti-channel network, which takes GPRS/CDMA and3G network as the primary andBeidou satellite system as the supplement. This combination has been proved efficientin practice.â‘¢An integrated terminal for multi-dimensional data has been developed by thecode system of monitoring data to synchronously realize data collection, transmissionand concentration.(5) Based on the findings mentioned above, tnternet-based early warning systemfor geohazards has been developed, which is combined with3D topography display,information query, analysis, real-time monitoring and automatic warning by database,GIS technology and so on.(6) The monitoring and early warning system of geohazards was applied in thestudied areas, Kaiyang of Guizhou province and three regions in Sichuan province(Yingxiu, Longchi and Qingping) during the period of rainy season in this year (2012).The result shows that the deformation condition can be obtained in time. It hassuccessfully warned the Wen-jiagou and Zou-maling debris flows on August17,shoing its applicability. This also testifies and supports, theoretically and practically,the methodoly in this study.