DAP ? Large Volume Spatial Data Discovery and Distribution over Networks

Abstract

The Internet, Intranets and general globalisation of networking technology have produced a dramatic increase in the type and volume of geo-data that are available to geoscientists. The development of useful protocols and underlying technologies for computers to access and share geo-data, both privately within organizations, and globally on the Internet is key to our ability to use this information efficiently. In this paper, we describe the Data Access Protocol (DAP), which is a suite of server applications that enable geoscientists to find and evaluate data, and automate windowing, reprojection and reformatting the data to suit a specific requirement. DAP technology addresses a variety of network situations including: 1. Simple web-browser based discovery and retrieval of data of interest in a specified format and coordinate system; 2. Support for Open GIS Consortium Web Map Server (WMS) interface to allow any WMS compatible application to retrieve ``images' of the data for use as layers in a GIS application; 3. Direct support for DAP-enabled thick clients, such as Oasis montaj, to optimally retrieve data directly for their own use, and transfer data to a hosting DAP environment. When communicating with DAP-enabled client applications, DAP addresses the movement of data (lossless compression, encryption and streaming) both to and from a data server over a network. The core DAP protocol effectively abstracts data formats to allow client applications to work in whatever environment is required, and DAP servers to connect to data in whatever native format is in use by a hosting organization. This makes DAP suitable for use in many data storage environments. DAP also includes a number of spatially optimised data stores that can be used to deliver extremely high performance for data extraction and retrieval.