16:30 〜 16:45
[SVC27-10] Web-based Tools for the Estimation of Tephra Fall Volume using WebGIS and Open-Geospatial Consortium (OGC)-Based Web Services
キーワード：Tephra Fall, Volume, WebGIS, OGC, WMS, WPS
Tephra fall volume data is very useful for understanding the nature of volcanic eruption and the extent of destruction caused by the phenomenon. Mathematical models used to estimate tephra fall volume are based on the relationship between thickness and area of volcanic debris as these values change from the vent to the farthest distance covered by the deposit. Tephra fall isopach contour maps in cm or isopleth mass contour maps in g/m2, which are derived from field data, are used for the estimation of tephra fall volume. Several models have been formulated to express thickness as a function of the isopach area. The most used models are the exponential (Pyle,1989), power law (Bonadonna and Houghton, 2005), and Weibull (Bonadonna and Costa, 2012). The segment integration method (Takarada et al., 2016), a modified exponential model developed at the Geological Survey of Japan, is also included. Computing tephra fall volume using the normal procedure is a time-consuming process involving the use of several software. This paper presents a web-based tool used to easily estimate tephra fall volume.
Web-based spatial information systems have recently been used as efficient and highly accessible platforms for processing geospatial information. The system is called WebGIS, which consists of a database and GIS software at the back end, and a webpage front end serving as interface. WebGIS provides spatial information processing capabilities through its web services that are accessible to the users. These web services are the Web Map Service (WMS) and Web Processing Service (WPS), formulated following the Open Geospatial Consortium (OGC) standards. WMS and WPS are used to render maps online and process geospatial data, respectively. Each of these web services has a corresponding Universal Resource Locator (URL). Spatial information processing is done by sending a request Universal Resource Identifier (URI) which consists of the service URL appended with request parameters.
This paper showcases the development of a WebGIS system used to estimate tephra fall volume using the exponential, power law, Weibull, and segment integration models. A spatial database for tephra fall data is created using the PostGIS software. WMSs are formulated to render tephra fall isopach and related geospatial data. WPSs are set up for the computation of tephra fall volume, which dynamically interacts with the system’s database for the computation of important parameters like isopach area. The services also use Google Chart API to plot the volcanic ash thickness and area lines during the computation. Innovative algorithms are also developed for automated segmentation and Weibull model kappa and lambda parameters estimation. Data entry is done by uploading tephra fall data in shapefile format. Alternatively, CSV data containing pairs of thickness and area can be pasted in using the system’s data entry interface. Comparison between volume estimation results using different models can be easily done using the system. The figure shows the tephra fall estimation system, showing the Aira tephra fall volume estimation result using the Weibull model.
Web-based spatial information systems have recently been used as efficient and highly accessible platforms for processing geospatial information. The system is called WebGIS, which consists of a database and GIS software at the back end, and a webpage front end serving as interface. WebGIS provides spatial information processing capabilities through its web services that are accessible to the users. These web services are the Web Map Service (WMS) and Web Processing Service (WPS), formulated following the Open Geospatial Consortium (OGC) standards. WMS and WPS are used to render maps online and process geospatial data, respectively. Each of these web services has a corresponding Universal Resource Locator (URL). Spatial information processing is done by sending a request Universal Resource Identifier (URI) which consists of the service URL appended with request parameters.
This paper showcases the development of a WebGIS system used to estimate tephra fall volume using the exponential, power law, Weibull, and segment integration models. A spatial database for tephra fall data is created using the PostGIS software. WMSs are formulated to render tephra fall isopach and related geospatial data. WPSs are set up for the computation of tephra fall volume, which dynamically interacts with the system’s database for the computation of important parameters like isopach area. The services also use Google Chart API to plot the volcanic ash thickness and area lines during the computation. Innovative algorithms are also developed for automated segmentation and Weibull model kappa and lambda parameters estimation. Data entry is done by uploading tephra fall data in shapefile format. Alternatively, CSV data containing pairs of thickness and area can be pasted in using the system’s data entry interface. Comparison between volume estimation results using different models can be easily done using the system. The figure shows the tephra fall estimation system, showing the Aira tephra fall volume estimation result using the Weibull model.