A Collaborative Virtual Geographic Environment Based on P2P and Grid Technologies*

Jun Zhu ^a,*, Jianhua Gong^a, Weiguo Liu^b, Tao Song^c, Jianqin Zhang^a

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^a State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing Applications, Chinese Academy of Sciences, Beijing 100101, China;

^b Department of Geography and Planning, The University of Toledo, Toledo, OH, 43606, USA

^c GIS Lab, Department of Geoinformatic Engineering, Inha University, Yonghyundong 253, Namgu, Inchon, S.Korea, 402-751

Abstract: Solving a geographic problem usually requires collaborative work among a group of people in different geographic locations. Collaborative virtual geographic environment (CVGE), an integrated technology, offers an intuitive, efficient, and interactive visualization environment through which geographically separated users can explore complicated spatial information and conduct collaborative work. In this paper, two new technologies, Peer-to-Peer (P2P) and grid computing, are tightly coupled to develop a CVGE system. This paper evaluates the potential contributions of the P2P and grid technology to CVGE systems. Using a Grid-based system architecture efficiently integrates and shares geographically distributed resources as well as modelling procedures built on different platforms. To offer a shared and interactive virtual collaborative geographic environment for resolving geographic problems, we developed several P2P services including a terrain visualization collaboration service and a video collaboration service. Finally, a CVGE prototype system is implemented for collaboration on silt dam planning on the Loess plateau. The experimental results show that the scheme developed in this paper is efficient and feasible.

Keywords: Collaborative Virtual Geographic Environment (CVGE); Peer-to-Peer (P2P); Grid Services; Open Grid Services Architecture (OGSA); Collaborative Work

1. Introduction

The advances in remote sensing, geographic information system (GIS), and other survey technologies over the course of last two decades have dramatically increased our capabilities to collect large amounts of multi-attribute geo-spatial data.  Geography has changed from a data and computation-poor discipline to an environment rich in data, computational tools, and resources. However, the value of geographic data cannot be fully realized when information content is difficult to describe and not successfully applied. Many datasets surpass the user’s ability to identify its gist and the underlying concepts because of their complexity (Lin and Zhu 2005). Visualization, an advanced technology of studying human-computer interaction, provides a new paradigm for visually and interactively exploring large amounts of complicated geo-spatial information. As an interdisciplinary of visualization and GIS, virtual geographic environment (VGE) was proposed in 1999. Unlike the traditional data-centered GIS, VGE is a human-centered environment that represents and simulates geographic environments (both physical and human environments). It allows geographically distributed multi-users to visually explore spatial information, design models, implement complex computation, and to provide support for decision-making (Gong and Lin 1999, 2000).

With the distributive nature of companies and research organizations, collaborative work among geographically dispersed workers has become very popular and important in both academia and industry. Research studies show that collaborative work involves the interaction of individual and group efforts where considerable complex information needs to be exchanged. Collaborative virtual environments (CVEs) are distributed virtual reality systems that offer graphical environments for individuals to exchange information and to work collaboratively. Collaborative virtual geographic environment (CVGE) integrates CVE and VGE to support collaborative work on geospatial information exploration and analysis by creating a digital landscape environment. It has drawn increasing attention in the fields of collaborative GIS and collaborative virtual environments (Wang 2002). The CVGE can be applied to many areas such as geographic game, public participation, city management and planning, resource development planning and management, natural disaster evaluation, prevention and reduction, collaborative scientific research, and virtual geographic education and training.

CVGE integrates the technologies of computer network, visualization, and spatial information. There are two important components in a CVGE system: distributed system architecture and virtually shared collaborative environment. Thus, the implementation of an open and flexible architecture and a more intuitive, efficient, and interactive visualization collaborative environment is crucial to the success of a CVGE system in the real world. The grid and Peer-to-Peer (P2P) technologies developed in the field of computer network provide such a platform for sharing resources and services across distributed, wide area networks. Integration of the two technologies with visualization in a CVGE system has become very promising.

Grid technologies aim at supporting resource sharing and problem solving in dynamic, multi-institutional virtual organizations (Foster et al. 1998). The essential property of Grid technologies is using services to implement different Grid functions requested by multi-users. By using grid computing, CVGEs can integrate and share all internal resources to create a high-performance computing environment (Foster et al. 2001, 2002a). Also, Grid technology based CVGE can integrate different kinds of services across distributed, heterogeneous, dynamic collaborative environment formed from the disparate resources within a single system and/or from external resources sharing and service provider relationships (Foster et al. 2002b). A true P2P system is one where all nodes in a network join together dynamically to participate in traffic routing-, processing- and bandwidth intensive tasks. It has many advantages over traditional client-server networks in terms of data sharing. With P2P, computers can share both data and resources through direct communication with each other (Georgios et al. 2004, Sudip et al. 2005, Cai et al. 2005). Thus, by using P2P, CVGEs can potentially improve the efficiency of resource usage and collaboration.

 This paper mainly focuses on the design and implementation of a collaborative virtual geographic environment system using Grid and P2P technologies. Several key techniques, such as data organizing and scene simplifying, which are needed to build a real time collaborative geographic scene, are discussed in the following sections. The system aims to efficiently integrate disparate resources and to offer powerful geographic information services, and to allow large-scale distributed users to explore spatial information and conduct collaborative work.

The remainder of this paper is organized as follows. In section 2, the features of Grid and P2P technologies are introduced and their advantages are discussed. In section 3, a Grid based CVGE system is presented and two types of P2P application services are designed. In section 4, a prototype system that includes a terrain visualization collaboration service and a video collaboration service is implemented. Finally, conclusions and future research plans are addressed in section 5