4 Progressive Techniques
81
• Concurrent Accesses: As with all online systems, a progressive transmission system should be able to handle many concurrent accesses. As the systems proposed
so far were mainly prototypes this aspect has not been fully analyzed.
• Thin vs Thick Client Solutions: While the server is provided with methods for
building, manipulating, and transmitting a sequence of map representations at
different levels of detail, depending on the device capabilities and bandwidth,
a client could be simply provided with either visualization functionality or a set
of operations for updating and integrating the transmitted levels as well as for analyzing and querying. Different caching techniques should also be investigated.
• Interoperability and Openness: So far mainly application-specific prototype
implementations, often not complying with interoperability specifications
[35, 46], have been developed.
Finally progressive transmission systems should make available, depending on
users’ purposes, a combination of raster and vector formats. Full comparisons on the
transmission of vector map versions and their rasterized counterparts have not been
conducted. It would be interesting to evaluate performance versus users’ requirements in different scenarios.
4.7 Conclusions
In this chapter, we have reviewed existing approaches to progressive transmission of
spatial data over the Internet. Successful and commonly used approaches are limited
to the transmission of raster images and triangular meshes. For these types of data,
compression mechanisms are effective and efficient. For more general spatial data
in vector format (e.g. map data), several challenges and open issues still remain that
have thus far prevented the successful implementation of effective progressive data
exchange. In this chapter, we have discussed these critical aspects and identified
research areas that still need much investigation.
The recent diffusion and popularity of mobile devices has given rise to a lot of
research into mobile GIS applications. Due to screen, bandwidth, and processing capabilities limitations, progressive vector transmission would be extremely beneficial
within this context. However, the same conceptual problems remain, and from an
implementation point of view, mobile device limitations impose even more impediments. Studies in this direction are still at an early stage.
References
1. Bajaj CL, Pascucci V, Zhuang G (1999) Single resolution compression of arbitrary triangular meshes with properties. In: Proc. of IEEE Data Compression Conference, 247–256
2. Ballard DH (1981) Strip Trees: A Hierarchical Representation for Curves. Communications of the ACM, 24(5):310–321
3. Barnsley M (1989) Fractals Everywhere. Academic Press, San Diego
81
• Concurrent Accesses: As with all online systems, a progressive transmission system should be able to handle many concurrent accesses. As the systems proposed
so far were mainly prototypes this aspect has not been fully analyzed.
• Thin vs Thick Client Solutions: While the server is provided with methods for
building, manipulating, and transmitting a sequence of map representations at
different levels of detail, depending on the device capabilities and bandwidth,
a client could be simply provided with either visualization functionality or a set
of operations for updating and integrating the transmitted levels as well as for analyzing and querying. Different caching techniques should also be investigated.
• Interoperability and Openness: So far mainly application-specific prototype
implementations, often not complying with interoperability specifications
[35, 46], have been developed.
Finally progressive transmission systems should make available, depending on
users’ purposes, a combination of raster and vector formats. Full comparisons on the
transmission of vector map versions and their rasterized counterparts have not been
conducted. It would be interesting to evaluate performance versus users’ requirements in different scenarios.
4.7 Conclusions
In this chapter, we have reviewed existing approaches to progressive transmission of
spatial data over the Internet. Successful and commonly used approaches are limited
to the transmission of raster images and triangular meshes. For these types of data,
compression mechanisms are effective and efficient. For more general spatial data
in vector format (e.g. map data), several challenges and open issues still remain that
have thus far prevented the successful implementation of effective progressive data
exchange. In this chapter, we have discussed these critical aspects and identified
research areas that still need much investigation.
The recent diffusion and popularity of mobile devices has given rise to a lot of
research into mobile GIS applications. Due to screen, bandwidth, and processing capabilities limitations, progressive vector transmission would be extremely beneficial
within this context. However, the same conceptual problems remain, and from an
implementation point of view, mobile device limitations impose even more impediments. Studies in this direction are still at an early stage.
References
1. Bajaj CL, Pascucci V, Zhuang G (1999) Single resolution compression of arbitrary triangular meshes with properties. In: Proc. of IEEE Data Compression Conference, 247–256
2. Ballard DH (1981) Strip Trees: A Hierarchical Representation for Curves. Communications of the ACM, 24(5):310–321
3. Barnsley M (1989) Fractals Everywhere. Academic Press, San Diego