Design of Distributed Interactive Online Geographic Information System Viewer using Wavelets

Abstract

The purpose of this work is to develop a distributed interactive online geographic information system (DIO-GIS) viewer using wavelet theory. Wavelet analysis is a new mathematical tool that transforms information into a multiresolution format. This allows efficient transmission of data upon clients’ requests. In DIO-GIS, a raster map is treated as a 2D function and decomposed into a nonredundant hierarchy of submaps by storing only the differences between the various resolutions. These differences in scale can be compressed, transmitted separately over the Internet, and then reconstructed up to the desired resolution by the client. A prototype DIO-GIS viewer is implemented using a wavelet scheme known as lifting to achieve a pure integer transform. This prototype demonstrates that the described approach can achieve similar compression to JPEG while providing a hierarchical decomposition of maps, which makes it very efficient in transferring large amounts of GIS data over low-speed networks. In particular, by coupling the compression algorithms with the ability to perform zooming and panning operations over networks, this prototype is able to eliminate redundant data transfer and achieve a smooth real-time image-browsing capability. This distinguishes it from other networked GIS browsers, which work with standard image file formats such as GIF and JPEG.