PNG Elevation Tile

- Design and implementation of the elevation file format for Web use -

Abstract

Because elevation data express the topography, and the formation of the topography greatly depends on the geologic factor, the utilization of elevation data is important geologically. In recent years, you can get elevation data of the various region or precision with progress of science and technology. But when judging from the angle as the web use, utilization is hardly developed by recent years' interactive Web site use. We designed the PNG Elevation Tile as a format to handle them at high speed on the web and built the test service to promote profit utilization of elevation data. By the PNG elevation tile, an elevation datum is treated for a 24 bit signed integer, and it is separated by 8 bit to RGB and is saved in a pixel. In comparison with existing technique, the PNG elevation tile has three advantages such as, small file size, easy processing and good visibility. And furthermore, we implemented elevation indication function of the Seamless Geological Map of Japan using PNG Elevation Tile, and built flooding simulation as test web application. Through this utilization, it was indicated that interactive web application can be built at high speed using PNG Elevation Tile, and the effectiveness of PNG Elevation Tile was demonstrated.