...al. 1991). Groupware has been defined as "technology that communicates and organizes unpredictable information, [thereby] allowing dynamic groups to interact across time and space" (Cameron et al. 1995). Each groupware system is designed to support a particular cooperative work situation or, a particular range of cooperative work situations. Although cooperative work settings are very diverse in terms of task, duration, group, organizational context, and culture (Hinssen 1998), they are usually classified as one of four situations characterized by their temporal and spatial dimensions (Johansen 1988; Dix 1996; MacEachren and Brewer 2004). These are: 1) same time (synchronous) and same place (co-located); 2) different time (asynchronous) and same place; 3) different time and different place (distributed); and 4) same time and different place.

A quick search of the literature reveals an overwhelming number of publications related to collaborative geographic information systems (GIS) (Churcher and Churcher 1996; Jones et al. 1997; Li and Coleman 2003; Balram and Dragicevic 2006), Geocollaboration (MacEachren and Brewer 2004; Cai 2005), or group spatial decision support (GSDS) (Armstrong and Densham 1995; Nyerges 1999; MacEachren 2001; Jankowski and Nyerges 2001). Most of these research efforts relate to group spatial decision support and the development and/or integration of group-based GIS technology with other computer technologies to facilitate group problem-solving, scientific visualization and decision-making with an inherently geographical character (Jankowski and Nyerges 2001). Nyerges and Jankowski (Nyerges 1999; Jankowski and Nyerges 2001) have pursued a systematic program of research focused on GIS-supported, same-time and same-place collaborative decision-making, design and implementation of group systems, and development and application of methods for evaluating these systems. Dragicevic and Balram (2004) focus on structuring and managing distributed planning processes with a Web GIS collaborative frame work, which enable remote users can share maps, annotations, and text comments at the same or different times. Stock and Bishop (2006) developed the so called envisioning system (EvS) for the study of community values and their interactions with a given landscape (3D models) in a workshop environment. The system uses virtual reality technologies and personal digital assistant (PDA) devices. Li and Coleman (2003) applied workflow and warehousing principles to a collaborative GIS data production environment.

Over the last few years, efforts to study human factors and/or human-computer interaction in GIS collaboration have increased. MacEachren and Brewer (2004) described a conceptual framework for geo-collaboration activities, which takes into account both human-centered (such as problem context, collaboration tasks, and perspective commonality) and system-oriented factors (such as temporal context, interaction characteristics, and tools to mediate group work) during the development and usability testing of such environments. Balram and Dragicevic (2006) presented a collaborative modeling framework with agent UML (AUML) to solve more complex interactions between "nature" and human systems.

However, the technologies and discussions referred to above are based on specific contexts or domains. This is because most collaboration functions are not generic. However, while the functions can be multi-dimensional and multi-disciplinary, collaborative features, such as map view sharing and participants' awareness, are in common, potentially creating the need to isolate and abstract them into a GIS application. Furthermore, previous research has not provided a definitive technical solution for collaboration computing in synchronous and distributed environments. The early efforts on synchronous collaborative GIS, e.g., Habanero (Chabert et al. 1998), Toucan Navigate (Toucan 2007) and GroupArc (Churcher and Churcher 1996), focused primarily on combining GIS with CSCW software (groupware). These developments usually used a commercial GIS system with a groupware extension (e.g., GroupArc: Arcinfo + GroupKit) or a groupware environment embedding a GIS component (e.g., Groove Framework and Toucan, Habanero and GIS viewer). Cai (2005) argues that these two approaches are equally bad strategies for geo-collaborative applications, encouraging heavy dependency on one or more particular CSCW, GIS, or other software systems, which then causes difficulties in terms of deployment, maintenance, and adaptation. In addition, these systems are mostly 2D, and few of them are web-based. Developing web-based synchronous collaborative 3D GIS with the desired collaboration functions remains a challenge.

The research presented in this paper attempts to bridge this gap by integrating the collaboration capability into a distributed 3D GIS system, using a component-based development approach. The synchronous collaborative 3D GIS framework thus developed is intended for data visualization and simple information retrieval in the context of group decision-making. The next section examines recent or current efforts on collaborative 3D, followed by a description of the synchronous collaborative 3D GIS (SC3DGIS) under study and how this research differs from the work done by others. We then discuss some important design issues before presenting a conceptual design of the proposed system. A preliminary prototype system is presented to demonstrate vital design issues. The paper concludes with observations on the research undertaken and its findings.

Collaborative 3D and SC3DGIS

Several state-of-the-art 3D GIS systems, such as 3D Analyst of ArcGIS from ESRI Inc., Image VirtualGIS from EADAS Inc., etc., are currently widely used by the GIS community. Their main functions are to provide 3D GIS data presentation (visualization) and simple 3D GIS data analysis and query. The Open Geospatial Consortium's Web Terrain Service (WTS) (WTS 2003) is an open standard for web-based 3D GIS to visualize terrain data (a kind of 2.5D data model). Some researches have used Virtual Reality Modeling Language (VRML, a true 3D data model) to visualize 3D GIS data in a web-based environment. Although some of these tools provide web-based visualization capability (or GIS-related query functions), even true 3D data models currently are unable to support real-time collaboration, due to a scarcity of distributed frameworks supporting multiple users' communication and cooperation.

The main commercial 3D GIS are still singleuser-based, standalone systems; examples are 3D Analyst of ArcView from ESRI Inc., Image VirtualGIS from EADAS Inc., GeoMedia Terrain from Intergraph Inc., and PAMAP model of PAMAPGIS from PCIGEOMATICS (Zlatanovaa et al. 2002). These systems are neither web based nor synchronously collaborated. While GeoVRML, has been investigated for web-based geospatial 3D data visualization and analysis (Rhyne 1999; Huang et al. 2001), most of the research conducted did not address real-time collaboration and, hence, distributed, multiple user's 3D frameworks. Gong and Lin (2006) described a collaborative virtual geographic environment (CVGE) in a distributed, three-dimensional geographical world. The system framework was based on client-server architecture, and a prototype system was developed with Java, Java3D, and VRML to explore the methodologies of collaborative spatial planning of silt dam systems. However, the client-server architecture of this 3D GIS is limited in how it handles real-time collaborative computing.

With the emergence of various 3D "digital earth" applications, such as Google Earth 3D (Google 2007) and Microsoft's 3D Virtual Earth (Microsoft 2007), we see the emergence of 3D systems with collaboration functions, mostly as extensions or add-on tools to the core and "heavy" system/server. Examples are TerraExplorer (Skyline 2006), Leica Virtual Explorer (Leica 2007), and Unype (Unype 2007). Through sending connection information, the users can get a shared 3D view using these systems. The connection information is identification among users such as user's email, user's IP address, etc. The Unype system is particularly interesting as it enables users to experience a multiuser Google Earth 3D (Skype 2006).

Close examination of these 3D systems provides a number of observations that are useful to our research. First, the collaboration tools cannot be stand alone and need to work with a heavy core system which normally includes a collaboration server handling synchronous collaboration (e.g., Toucan Navigate) and a global dataset server providing 3D data and images such as Google Earth 3D. This kind of "heavy" architecture hinders the system extendibility and scalability, making it difficult to extend these systems to meet application-oriented requirements related to collaborative 3D GIS. Second, the 3D systems do not support true 3D models. Almost all of them are 2.5D systems focusing primarily on large-scale (city level) data models. Third, not all 3D systems have extension or add-on tools for real-time, synchronous sharing of 3D views. For example, both Google Earth and Microsoft Virtual Earth only allow asynchronous sharing of maps and 3D views through emailed links.

On the other hand, many non-GIS...

NOTE: All illustrations and photos have been removed from this article.



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