Title of Paper: Interoperability between Digital Earth and DODS

Principal Author: Chris Lynnes

Abstract: Remote sensing datasets can be obtained from a plethora of sources in myriad formats.  Both the distributed sources and format heterogeneity create difficulties for users attempting to use multiple data sets together.  Several systems have been designed to address this need for data access interoperability, among them the Digital Earth (DE) system based on the Web Mapping Testbed (WMT) technology from OpenGIS and the Distributed Oceanographic Data System (DODS).  WMT seeks data access and interuse primarily in Geographical Information System clients, while DODS has been focused on such numerical analysis clients as Ferret, GrADS, Matlab and IDL.

In order to bridge the differences, an effort has been underway to enhance DODS to support the DE/WMT protocols.  A WMT gateway server acts as a DODS client application, parsing the WMT request to determine the URL to a remote DODS-served dataset.  Using information from the remote server, the gateway also determines the proper subset constraints to fulfill the region asked for in the WMT request.  Then, the gateway retrieves the subsetted data from the server and applies several transformations (e.g., interpolation, reprojection, rasterization) to return a map to the DE/WMT client making the GetMap request.  The WMT-DODS gateway application provides generalized interfaces for a number of site-specific specializations that could be performed on the returned dataset; the generalized interfaces allow extensions to support additional projections, interpolation algorithms, map stylizations, and output formats.

One benefit of the overall approach is an easy path for existing DODS data providers to participate in Digital Earth interoperability.  The design provides an added benefit:  the utilization of the DODS client-side core allows the gateway to access data from multiple sites and incorporate them into a single map.