Geospatial Service Oriented Architectures for Mobile Augmented Reality Thierry Badard1 1
Centre for Research in Geomatics, Department of geomatic sciences, Laval University Québec, Qc, Canada G1K 7P4 Tel. +1 (418) 656-7116 Fax +1 (418) 656-7411
[email protected], http://geosoa.scg.ulaval.ca KEYWORDS: Geospatial Service Oriented Architectures, Web Services, Interoperability, Mobile applications, Augmented Reality 1. Introduction Data dealing with our spatial environment move more and more from 2D representations to actual 3D worlds. Maps, aerial photographs are more and more replaced by 3D models in which the relief and the characteristics of the elements (building, vegetation...) in the scene appear. This visualisation mode of information is more natural for a user because it better corresponds to its perception of a real environment. Many applications can benefit from this 3D modeling of the data: civil safety (intervention after natural disasters, flood or fire), military defence, etc. The stake consists on the one hand in knowing well the ground of intervention before going there, then on the other hand, once on the spot, in having access in real time to information on the evolution of the ground, in order to move and intervene in a safe and effective way. The 3D models then propose "faithful" representations of the reality. General public can also benefit from this three-dimensional new mode of representation to guide and locate themselves within urban environments. On demand web services for maps delivery (e.g. standard WMS - Web Map Service, (OGC, 2006)), or services such as Google Earth start to propose maps of cities to sedentary or mobile users, in which the buildings or the principal monuments appear in 3D. Even if the photo-realistic portrayal of these representations remains still largely perfectible, it becomes more intuitive to users to locate in such 3D environments. Delivery over Internet or dedicated to mobile users of such environments or more simply of photorealistic objects in 3D is still in its infancy. Indeed, even if the technologies based on XML such as VRML, geoVRML or X3D (ISO, 2004) start to make possible the delivery of 3D scenes on diverse networks, it remains a long (research) work before achieving the real time delivery of complete interactive photo-realistic environments of virtual reality (Kalawsky, 2004) or augmented reality (AR) scenes. Such environments are composed of scenes where 2D or 3D objects, audio or textual information are added to the user vision of the real environment and with which this one can interact. These objects or information are generally provided, in real time, according to the location of the user, its "surrounding" and its context of use (personalisation, user preferences, etc.). This type of technique would greatly increase the immersive aspects and interactivity of the produced scenes and, would enrich the user perception of its spatial surrounding. For example, the firemen which intervene in a building on fire could, according to their location in the building, the position of the other operating teams, their mission affected by the headquarters, have their vision of the reality of the intervention scene augmented in real time. A map of the building with location of the other teams, a video showing what a particular team is facing, on demand detailed maps of a peculiar part of the building could thus be elements which would come to be added to their vision of the theatre of the operations.
2. Towards Geospatial Service Oriented Architectures for Mobile Augmented Reality However, at the present time, interactivity in this type of environment is very limited. Users can only interact with the objects which are in the vicinity or interact with other users present in the same environment in a very limited way. Increasing interactivity would require that the infrastructures enabling Internet and mobile delivery of 2D and 3D geospatial data, could deliver: 1) multiple representations of objects (in 2D or 3D) linked the ones with the others to allow navigation at different levels of detail, representation or scale; 2) consistent representations of data digitalised or captured independently the ones from the others 3) online processes which enable the real time delivery, analyse, modification, derivation and interaction with the different levels of scale and detail of the geospatial data. These online processes are called Web services. According to the definition of a Web Service provided by the W3C (W3C, 2004), “a Web Service is a software system designed to support interoperable machine-to-machine interaction over a network. It has an interface described in a machine-processable format (specifically WSDL (W3C, 2001)). Other systems interact with the Web Service in a manner prescribed by its description using SOAP (W3C, 2003) messages, typically conveyed using HTTP with an XML (W3C, 2004) serialisation in conjunction with other Web-related standards”. In other words, a Web Service is a set of related application methods that can be remotely accessed across a network (such as a corporate intranet or Internet itself). The information that an application must have in order to programmatically invoke a Web Service is given by a Web Service Description Language (WSDL) document. WDSL documents will be indexed in searchable Universal Description, Discovery, and Integration (UDDI) Business Registries (OASIS, 2006) so that developers and applications can locate Web Services. Web Services are powered by Web applications servers that speak Simple Object Access Protocol (SOAP), and deliver information marked up in eXtensible Markup Language (XML). All Web Services available on the internet as a whole are called the Service Web. The Service Web will be the backbone of the next generation of distributed applications. Today, the Service Web is in its infancy, but is very promising. The principal goal of Web Services is then to provide interoperability between typically distributed application components. Applications may have been built on a variety of different systems (e.g. Unix, Windows, legacy mainframe systems), using different programming languages, on different middleware, using different data stores. Web Services enable these disparate components to interact by providing a standard set of technologies, which can describe themselves, be found and be invoked. 2.1. Why geospatial web services for mobile AR ? As mentioned in (Zeichick, 2003), mobile devices will not always be connected, and when connected, there is no way to guarantee or even predict bandwidth and reliability, or even jitter and delays in communication. Thus, the classical client-server architecture, which presumes always-on broadband-is rarely suitable for wireless communications. While it may seem easy to put all of the program logic on the server, and only place a user-interface stub on the client, users may find the experience to be unsatisfactory, due to unpredictable network availability. A more resilient model consists in developing a full-featured client application and in instructing it to use Web services to interact with the server application. When the systems are connected, Web services messages (each consisting of a Simple Object Access Protocol (SOAP) packet with an eXtensible Markup Language (XML) payload) can relay instructions and data across the network, refreshing the client app's data and carrying out network-based requests. If not connected, a message queue can hold Web services messages, while still allowing the mobile app to provide a level of functionality. It's a different paradigm than standard client/server, but may be better suited to the needs of mobile users, especially in Augmented Reality context where users expect that their experience is satisfactory.
In addition, current geospatial Web services are very often limited to those specified by the Open Geospatial Consortium (OGC) and standardised by ISO, namely the Web Map Service (OGC, 2006) (service for the online delivery of 2D maps), Web Feature Service (OGC, 2005) and Web Coverage Service (OGC, 2003) (services for the online delivery of respectively geospatial vector and raster data). If these services constitute the essential building blocks for the design of distributed and interoperable infrastructures for the delivery and access to geospatial data, no processing is possible. Online Analysis, data matching (Badard, 2000; Badard and Lemarié, 2002) or correlation, update propagation (Badard, 2000; Badard and Lemarié, 2000), derivation or creation of new information, etc. is currently not possible with such services. Thus these services the ISO 19119 standard (OGC, 2002) categorises as being processing Web services for geospatial information, remain completely to be invented. 2.2 GeoSOA The research objectives aimed by the author thus deal with the establishment of the fundamental, generic and reusable concepts allowing the definition of interoperable, open and distributed infrastructures, enabling the Internet and mobile delivery of 2D and 3D multi-representations geospatial data and the design of geospatial web services for the online processing of this information in real time. This could be summarised under the acronym GeoSOA, which stands for Geospatial Service Oriented Architectures (for real time Internet, mobile and wireless location based services delivery to users), see http://geosoa.scg.ulaval.ca. This research work also aims at initiating the specification of methods which provide such an infrastructure with capabilities of intelligence and autonomy. This could be performed through the definition of high level services which define the chaining and automate the remote call (with the right parameters) of the relevant and distributed services which are needed to achieve a specific task. Such a capability is named intelligent orchestration of geospatial Web services. If a lot of research works have dealt with methods and tools for the modeling, the design (Devogele, 1997) and the of update (Kidner, 1996; Badard and Lemarié, 2000) of multi-representations (MR) 2D geospatial databases, only a few are related to the design and the update of data warehouses mixing 2D and 3D representations. Work dealing with 3D data are more focussed on the methods for modeling the objects themselves (De-La-Losa, 2000), the definition of associated query languages (De-La-Losa, 2000), and the design of algorithms for the implementation of such models based on different types of image (Tao and Hu, 2002) or dedicated to their visualisation (De-La-Losa, 2000; Han, 2003, Kalawsky, 2004).
Figure 1. Geospatial Web Services for Mobile Augmented Reality Figure 1 illustrates the organisation of the services (in gray) which are planed to be developed in a near future in order to provide a distributed and interoperable infrastructure of processing web services for the implementation of mobile geospatial Augmented Reality applications. The white boxes deal with examples of geospatial web services which will be investigated, within a short or long term period, within research projects not specifically dedicated to Mobile Geospatial Augmented Reality. 3. Conclusion This paper has illustrated the concept of Geospatial Service Oriented Architectures (GeoSOA) and its relevance in the definition of distributed and interoperable multi-representation data infrastructures to enhance the experience of the users in mobile augmented reality applications. First experiments in the development of such geospatial processing web services have been performed in (Badard and Braun, 2003). They are based on the GeOxygene platform, which has been mainly designed and developed by the author and Arnaud Braun and is now available as an open source project, see http://oxygeneproject.sourceforge.net.
References Badard, T. and Lemarié, C. (2000). Propagating updates between geographic databases with different scales. Chapter 10 of Innovations in GIS VII: GeoComputation, Atkinson, P. and Martin, D. (Eds.), Taylor and Francis, London, UK, 12 pages. Badard, T. (2000). Propagation des mises à jour dans les bases de données géographiques multireprésentations par analyse des changements géographiques. Mémoire de thèse de doctorat en Informatique de l'Université de Marne-la-Vallée, spécialité : Sciences de l'Information Géographique, Marne-la-Vallée, France, 115 pages.
Badard, T. and Lemarié, C. (2002). Associer des données : l'appariement. Information Géographique et Aménagement du Territoire (IGAT), Traité de Géomatique, Généralisation et représentation multiple, Chapitre 9, Hermès sciences, Lavoisier, Paris, pp. 163–183. Badard, T. and Braun, A. (2003). OXYGENE: An open framework for the deployment of geographic web services. In proceedings of the 21st International Cartographic Conference (ICC 2003), ICA/ACI Editors, August 10-16, 2003, Durban, South Africa, pp. 994-1004. De-La-Losa, A. (2000). Modélisation de la troisième dimension dans les bases de données géographiques. Mémoire de thèse de doctorat en Sciences de l’Information Géographique de l'Université de Marne-la-Vallée, Marne-la-Vallée, France. Devogele, T. (1997). Processus d'intégration et d'appariement des bases de données géographiques. Application à une base de données routière multi-échelles. Mémoire de thèse de doctorat en Informatique de l'Université de Versailles, Saint-Quentin en Yvelines, France. Han, H. (2003). 3D Browser for Open GIS Web Services, GIM International, Vol. 17, No. 3, March 2003. International Organisation For Standardization (ISO) (2004). ISO/IEC 19775:2004 – Extensible 3D (X3D), 2004-12-01. Kalawsky, R. S. (2004). The science of virtual reality and virtual environment, 2nd Edition, AddisonWesley Pub., 2004 Kidner, B.D. (1996). Geometric signatures for determining polygon equivalence during multi-scale GIS update. Second Join European Conference & Exhibiion on Geographical Information, Barcelona, Spain, IOS Press, pp. 238–247. OASIS Open (2006), Universal description, discovery and integration (UDDI), OASIS — http://www.uddi.org. OpenGeospatialTM Consortium (OGC) (2002). The OpenGIS® Abstract Specification – Topic 12: The OpenGIS® Service Architecture (ISO 19119 Geographic Information Services), version 4.3. OGC document number: 02-112. OpenGeospatialTM Consortium (OGC) (2003). OpenGIS® Web Coverage Service (WCS) Implementation Specification, version 1.1.0. OGC document number: 03-06r6, August 2003. OpenGeospatialTM Consortium (OGC) (2005). OpenGIS® Web Feature Service (WFS) Implementation Specification, version 1.1.0. OGC document number: 04-094, May 2005. OpenGeospatialTM Consortium (OGC) (2006). OpenGIS® Web Map Service (WMS) Implementation Specification, version 1.3.0. OGC document number : 06-042, March 2006. Tao V. and Hu Y. (2002). 3D reconstruction methods based on the rational function model, Photogrammetric Engineering & Remote Sensing, 68(7): 705-714. Zeichick, A. (2003). The Four Critical Issues for Mobile Apps Developers – Are you aware of the four main issues facing mobile developers? http://www.devx.com/Intel/Article/10640. World Wide Web Consortium (W3C) (2001). Web Services description language (WSDL) 1.1, W3C (March 2001) — http://www.w3.org/TR/wsdl. World Wide Web Consortium (W3C) (2003). Simple object access protocol (SOAP), W3C (June 2003) — http://www.w3.org/TR/soap. World Wide Web Consortium (W3C) (2004) eXtensible Markup language (XML), Specification version 1.1 — http://www.w3.org/XML/. World Wide Web Consortium (W3C) (2004). Web Services architecture, W3C (February 2004) — http://www.w3.org/TR/ws-arch/. Biography Dr. Thierry Badard is professor in the Department of geomatic sciences at Laval University. Member of the Centre for Research in Geomatics, he is an expert of international standards in geomatics and Internet technologies. His research interests deals with (web) Service Oriented Architectures (SOA) for the interoperable and distributed processing of transactional or decisional geospatial information, its real time delivery and the design of innovative applications dedicated to mobile devices.
