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Designing a Real-Time Mobile GIS


4 Performance Evaluation
The model discussed in this paper has been simplified with the following assumptions:
  1. Time is one-dimensional and linearly ordered;
  2. Relational databases are used to develop the GIS model;
  3. Connection to the server and data retrieval via an active TCP/IP connection using the Hyper Test Transfer Protocol (HTTP) utilized as data transfer protocol; the Mobile user provides an initial position.
A simplified location-based service has demonstrated how the Real-Time dynamic database works. A mobile user chooses a district, a current location, pass and destination points, and maximum walking distance. Based on the above criteria, the optimum path can be found and displayed on the mobile device. We characterize the performance of this function in the following way. The average response time from the mobile client is measured as the time spent (in seconds) from the moment the query is issued to the moment the results of the query are generated.

4.1 Analysis of the Results
The result is depicted in Fig. 4, which is plotted as a two-dimensional graph to illustrate the results of average response time. The line with square nodes corresponds to the time measurement from the dynamic database, while the line with diamond nodes represents the time measurement from the original database. We observe that the time saved increases as the database size expands. For the number of records, over 60,000, the time required in the original database is three times more than that in the Real-Time dynamic database. It is noted, however, that this is related to the actual time of the query, since the database volume is varied as time changes. The response time is slightly different to the result shown in Fig. 4. Nevertheless, we can easily discover that the time response on the Real-Time dynamic database is faster than the original database.


Fig. 4. Average response time.

5 Conclusions
This paper described a new conceptual model – a spatial temporal data set for mobile GIS and correspondingly a Real-Time dynamic database. In traditional GIS, spatial objects are the primary focus whereas in mobile GIS, the focus has been changed to a particular scene of a particular location at a particular time. The relevant objects are only a subset of the overall objects in the GIS and meaningful to the mobile user for a particular situation – involving location and time. The Real-Time dynamic database is automatically updated to mirror the current world. The application and test were developed using a wireless web GIS environment. We compared the difference between a traditional database with the proposed Real-Time dynamic database in terms of response. From the results we can see that the processing time of the conventional database is proportionally increased with the data size in the database while the response time can be dramatically reduced in the proposed Real-Time dynamic database. This is even more effective for a database with a large data volume. In the Real-Time dynamic database, the response time is minimized and query accuracy is improved. These two advantages will greatly benefit mobile users in their applications.

References
  • Aberdeen Group, Inc. (2000) The Benefits of Mobilising Enterprise Applications with Handheld Devices, August 2000
  • Chan Y, Si A, Leong HV (1998) Cache Management for Mobile Databases: Design and Evaluation. Data Engineering, 1998, Proceedings, 14th International Conference, 1998, pp 54-63
  • .Coates P (2000) Mapping and the Mobile Future, GI News, June 2000
    CONNECT Computer Corp. (2000) What is Thin Client Computing? [online] Available from: http://www.connectcomputer.com/thin-client.asp [Accessed 13 December 2001]
  • Darwen H, Date CJ (2000) Temporal Database Systems. Advanced Database Technology and Design, 2000, pp 137-187
  • Dent BD (1997) The Map Design Process and the Elements of Map Composition. In: Cartography Thematic Map Design, pp 236-267
  • Dunham MH, Kumar V (1998) Location Dependent data and its Management in Mobile Database [ online]. Available from: http://ieeexplore.ieee.org/iel4/5718/15304/ 00707433.pdf [Accessed 15 December 2001]
  • Francica J (2000) Location-Based Services Wireless Meets GIS. GEOWorld, December 2000
  • Hanttula D (2001) The Future of the Pocket PC. SemperAptus.com, January, 2001
  • Hecht L (2000) Stand up for Standards. GEOEurope, September, 2000
  • Iyengar SS, Pangburn BE (1998) Real-Time Computing: Meeting the Client's Demand for Data Access via the Internet. In: IEEE Workshop on Application-Specific Software Engineering Technology, ASSET-98 Proceedings. 1998, pp 14-19
  • Koeppel I (2000) What are Location Services? - From a GIS P erspective [online]. Available from: http://www.jlocationservices.com/company/esri/What%20are%20%Location%20Services.html [Accessed 8 July 2001
  • Laurini R (2001) Real Time Spatio-Temporal Database. Transactions in GIS 5(2)
  • Ka-wai Kwan and Wen-zhong Shi, A Study of Database in Mobile GIS
  • Lauzac SW, Chrysanthis PK (2001) Programming views for mobile database clients [online]. Available from: http://ieeexplore.ieee.org/iel4/5718/15304/00707432.pdf [Accessed 17 December 2001]
  • Lowe JW (2001) Which Where Will Win? Dueling Wireless Location Solution. Geospatial Solutions, March 2001
  • Meshulam Y (2001) says report HK Economics Times, 10 October 2001.
  • Mirghafori N, Fontaine A (1995) A Design for File Access in a Mobile Environment. In: Proceedings Workshop on Mobile Computing Systems and Applications, 1994. 1995, pp 57-62
  • Open Location Services Initiative (2001) [online]. Available from: <Open Location Services: Vision and Objectives, Corporate Roles and Work Program Summary> [Accessed 16 December 2001]
  • Palm Inc (2000) Wireless Enterprise Application for Mobile Information Management [online]. Available from: http://www.palm.com/pdfs/wireless_ent_apps.pdf [Accessed 15 December 2001]
  • Peuquet DJ (1999) Time in GIS and Geographical Database. Geographical Information Systems, Vol. 1, 2nd Ed. pp 91-103
  • Mobile-GIS, www.esbic.com
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