Laits' Papers

The Integration of Grid Technology with OGC Web Services (OWS) in NWGISS for NASA EOS Data

Liping Di, Aijun Chen, Wenli Yang and Peisheng Zhao
Center for Earth Observing and Space Research, School of Computational Sciences,
George Mason University, Fairfax, Virginia 22030, USA
lpd@rattler.gsfc.nasa.gov; achen6@gmu.edu

Abstract:
Grid technology provides secure, fundamental methods for advanced distributed computing and data sharing over the Internet. The technology has been used in applications in many disciplines. However, applications in the geospatial disciplines are just beginning. This paper describes a project that applies Grid technology to the Earth observation environment through the integration of the Globus Toolkit with the NASA Web GIS Software Suite (NWGISS). As one of the implementations of Open GIS Consortium’s (OGC) Web Services (OWS) technology, NWGISS is a web-based, multiple OGC-standard compliant geospatial data distribution and service system. It provides geospatial data access services to data users for Earth observing data archived in individual data centers (e.g., NASA Distributed Active Archive Centers, DAACs). But it does not provide secure on-demand distributed geospatial data processing and transfer among the data centers. In this project, Grid technology has been used successfully to solve these problems and a prototype Grid-enabled OGC-compliant NWGISS system was produced. This prototype is part of a large Committee on Earth Observation Satellites (CEOS) testbed for evaluating the usability of Grid technology in the geospatial disciplines, especially in Earth observations and remote sensing.

Keywords: Grid, Globus, OGC, OWS, Geospatial Data, NWGISS

1 Introduction
Grid is a promising technology for easily sharing distributed heterogeneous computing resources. It brings together geographically and organizationally dispersed computational resources, such as CPUs, storage systems, communication systems, data and software sources, instruments, and human collaborators to provide advanced distributed high-performance computing to users [1][2]. Globus, consisting of a set of services and software libraries, is the key middleware that provides core Grid capabilities. The Globus Toolkit facilitates the creation of usable Grids, enabling high-speed coupling of computers, databases, instruments, and human expertise. With Globus, scientists can run their gigabyte-per-time-step job on multiple high-performance machines at the same time, even though the machines might be located far apart and owned by different organizations. Grid technology helps scientists to deal with very large datasets and carry out complex remote collaborations. It can be used for large distributed computational jobs, remote instrumentation, remote data transfer, and shared immersive storage spaces [3].

Geospatial data are those that can be located on Earth. Earth observations through remote sensing are by far the largest source of geospatial data. The NASA’s Earth Science Enterprise (ESE) is generating a huge volume of remote sensing data daily for supporting Earth system science and application research through its Earth Observing System (EOS) project. Most of the EOS data are in HDF-EOS, the standard format for NASA’s Earth Observing System (EOS) Data and Information System (EOSDIS). These data are vitally important to studying global changes [4]. Therefore, making those data widely, easily, and freely accessible to users will greatly facilitate the global change research.

OWS is one of OGC’s many initiatives for addressing the lack of interoperability among systems that process georeferenced data. In the past several years, OGC has successfully executed several phases of the OWS initiative, including Web Mapping Testbed I (WMT-I), WMT II, OWS-1.1, and OWS 1.2. Those initiatives have produced a set of web-based data interoperability specifications, such as the OGC Web Mapping Specification (WMS), which allows interactively assembling maps from multiple servers, and the OGC Web Coverage Service (WCS) Specification, which defines interoperable interfaces for accessing geospatial data, especially those from remote sensing, from multiple coverage servers [5].

As a member of OGC and a participant of those OGC interoperability initiatives, LAITS at GMU has developed an OGC-specification compliant software package called the NASA Web GIS Software Suite (NWGISS). It is a web-based, multiple OGC-specification compliant, geospatial data distribution and service system for delivering NASA EOS data to broad user communities. Currently, NWGISS consists of a Web Map Server (WMS), a Web Coverage Server (WCS), a Web Catalog Server (WCAT), a Multiple-Protocol Geoinformation Client (MPGC), and a toolbox [4][9].

The Committee on Earth Observation Satellites (CEOS) is an international organization responsible for coordinating international civil spaceborne missions designed to observe and study the planet Earth. Its membership encompasses the world's government agencies responsible for civilian Earth Observation (EO) satellite programs, along with agencies that receive and process data acquired remotely from space. Inspired by the successful applications of Grid technology in other disciplines, the CEOS Working Group on Information Systems and Services (CEOS WGISS) started a CEOS Grid testbed in September 2002 to evaluate the feasibility and applicability of Grid technology to the EO community. The testbed, currently consisting of applications from NASA, USGS, NOAA and ESA, aims to address the use of grid technology for efficient support to diverse users worldwide for easy access and applications of EO data and to EO data providers for improving their efficiency of operation and maximizing the usefulness and benefit of the EO data which they gather [6].

As one of the NASA representatives to the CEOS Grid testbed, LAITS is contributing to the testbed by integrating OGC technology with Grid technology through the development of a Grid-enabled NWGISS. This paper describes our contributions.

References

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