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Lookup NU author(s): Sanphet Chunithipaisan, Professor Philip James, Emeritus Professor David Parker
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This paper reports on research into the development of generic, topology-aware, spatial datasets and models for spatial network applications. Currently, one of the most important challenges for Geographic Information Systems (GIS) is the generation of corporate geo-spatial resources whose full potential can only be realised by making them accessible to a large number of applications and end-users [18]. In the field of facilities management, such as gas, electricity, water, telecom and transportation companies, spatial network GIS could provide a useful graphical interface and geographical database for the management of network assets and flows [8]. Utility networks typically impact on many people over vast areas and are generally managed by government departments, large organizations or companies. There is often little collaboration between the organisations despite similarities of interest and in some cases new legal requirements to share data with other utilities to minimise the impact of repairs and new build on both the public and the environment [17]. Thus, there is a growing need both to share the basic network information and in some cases to integrate data sets to carry out more complex network analysis operations. In the real world, objects are connected to each other: thus an optical cable is connected to a multiplexer that in turn is connected to copper cables connecting into our homes to provide cable TV, telephony and internet access. Using GIS in support of network utility management typically involves many types of features that may have connectivity to each other. Several GIS vendors have developed GIS software whose potential functions can provide for network management and analyses [6], but each system has a proprietary format to deal with the connectivity between geometry or features. Topology in GIS is generally defined as the spatial relationship between such connecting or adjacent features [1, 4], and is an essential prerequisite for many spatial operations such as network analysis [16]. There are, in general, three advantages of incorporating topology in GIS databases: data management, data correction and spatial analysis [9]. Topology structures provide an automated way to handle digitising and editing errors, and enable advanced spatial analyses such as adjacency, connectivity and containment [2]. In some systems this relationship is assumed (by the user) whereas in others it makes up part of the structure of the geometry [1, 15]. In some systems topology can be built where all arcs intersect or touch [3] and in others rules defining connectivity between feature types can be used to build topology [5]. The reusability of existing data is a benefit for new applications [14]. This is often not possible because of problems with data integration due to proprietary data formats. Although attempts have been made to integrate formats using standards such as GML [11] and tools such as FME [12], there is a particular problem in network GIS in that topology is not exchanged in general import/export (other than that assumed by the geometry). In order for network analysis to be carried out the current options are to import data into your tool of choice, coercing data into the required format. If further changes are made to the original dataset then the process needs to be repeated. The data conversion across systems is however not straightforward and is similarly time consuming. Furthermore, the data about the same feature type may be separated and maintained in different systems. To distinguish the duplicated features when converting to the new database or importing to the new network analysis application is a difficult process. Even at the semantic level, inconsistencies in definition cause problems: for example, a feature, such as a road, may be labelled differently (e.g. as a street) in a different system. This paper reports on an on-going research project entitled “The development of generic, topology-aware spatial datasets and models”. This research has been undertaken to address and solve those problems mentioned above. We started by studying the real-world features and their spatial and aspatial properties. Using an object-oriented design concept, the data model of features has then been constructed. The ISO Spatial Schema [7] and the OGC Feature Geometry Specifications [10] were adopted and adapted for the conceptual data model used in the research. The geometry and topology were treated as a property of the feature object. The connectivity of real-world features was also investigated to understand how they connect and the ways in which they can connect. A “Family” of connectivity was a concept established for handling the connectivity between features in the network. Most GIS support a relational database, so an RDBMS was chosen for storing the geo-spatial data, to alleviate the problem of proprietary data formats. The application was implemented using the Java programming language, and JDBC [13] was used for connecting to databases. Several tools were created to support the application, especially for network analysis. The tool for building topology was created and tested to build topology based on the rule specified in the family. The network analysis functions - network follower and shortest path - are also developed, additionally supporting the directional network problem. Real world implementation, case studies and integration into a web based service model are on-going projects. The research investigated the conceptual data model to handle the topology, and network connectivity, and an application is being implemented to test the concept of our network connectivity model. The full paper will provide more details of the stages listed above: real-world feature model, network connectivity model, the concept of network family and the research implementation. Many of the tools supporting the data integration have been implemented and the developed application will be transferred to a web-based application which is the future work of the research. References 1. Burrough, P. and McDonnell, R. Principles of Geographical Information Systems. Oxford University Press Inc., New York. 2000. 2. David, M. Understanding Topology and Shapefiles. ArcUser April-June 2001. 3. ESRI. Online ArcInfo help. Clean command. 4. ESRI. The GIS Glossary, http://www.esri.com/library/glossary/t_z.html. 5. GE Smallworld. Online application help. Data Modelling – 5.2 Modelling geometry. 6. GE SmallWorld Network Solutions http://www.smallworld.co.uk/english/products/utilities/. 7. ISO. ISO/TC 211 Geographic information – Spatial schema. 8. Kosters, G., Pagel, B.-U. and Six, H.-W. GIS-application development with GeoOOA. International Journal of Geographical Information Science. 11, 307-335, 1997. 9. Legault. Topology in GIS Software. GEO Asia Pacific December/January 1999. 10. Open GIS Consortium. The OpenGIS Abstract Specification – Feature Geometry. http://www.opengis.org/. 11. Open GIS Consortium. Geography Markup Language (GML) 2.0. http://www.opengis.org/. 12. Safe Software. FME: Feature Manipulation Engine. http://www.safe.com/. 13. Sun. The JDBC API. http://java.sun.com/products/jdbc/overview.html. 14. T. Devogele, C. Parent, S. Spaccapietra. On Spatial Database Integration. International Journal of Geographic Information Systems, Special Issue on System Integration. Vol. 12, No 3, 1998. 15. Tarle, T. L. Topology - Why Bother?. GIS '95 Conference Proceedings. Fort Collins 1995. 2:736-738. 16. Timms, T. Relationship and Behaviour in GIS. Proceedings of the Association for Geographic Information (AGI) 4th National Conference. 1992. 17. UK Street Works Act. http://www.street-works.dtlr.gov.uk/. 18. Valsecchi, P., Claramunt, C. and Peytchev, E. OSIRIS: An inter-operable system for the integration of real time traffic data within GIS. Computers, Environment and Urban Systems, 23(4), 245-257, 1999.
Author(s): Chunithipaisan S, James PM, Parker D
Publication type: Conference Proceedings (inc. Abstract)
Publication status: Published
Conference Name: Map Asia 2002 Conference
Year of Conference: 2002
URL: http://www.gisdevelopment.net/technology/gis/techgi0065.htm
