Some Issues of Multi-dimensional and Dynamic GISs

For some traditional GIS application fields such as urban management and mining, the use of the technology was previously restricted by the static 2-dimensional GIS databases.With the rapid development of earth observation technology, large volumes of spatial information become available in an increasing updating frequency.As one direct benefit of such development, multi-dimensional and multi-temporal data become more readily available in the fields such as surveying and mapping, oceanography and environment.This stimulates the expansion of GIS technology to include dynamic 3-dimensional (or multi-dimensional) data and to develop associated data handling and processing methodology.Recently, for better understanding the earth environment and to support the sustainable development, a concept of dynamic multi-dimensional "digital earth" has emerged based on multi-resolution geo-spatial data. However, new challenges have been raised on maintaining and analyzing the spatio-temporal data synthetically and dynamically.The key issues include: (1) The data models and data modeling methods used by current commercial GIS software are basically designed to handle 2-D static spatial objects.It is difficult for them to represent dynamically changing 3-D spatial objects and to support Internet based interoperation among distributed heterogeneous multi-dimension spatial data; (2) The maintenance of topological relations and data access for multi-dimension data are much more complicated than those of the 2-D data.Simply extending the traditional methods used in 2-D to handle multi-dimensional data would hardly meet the new requirements.For instance, we could not simply extend 2-D Morton Code for accessing 3-D spatial data; (3) For multi-dimension spatial data, new methods need to be developed for data interpolation, visualization and human-computer interaction. Recent years we have witnessed a rapid growth of research interest and applications on multi-dimensional data handling and modeling.Large volumes of literature become available in various conference proceedings and international journals.International Society for Photogrammetry and Remote Sensing (ISPRS), being the leading professional group in the field, plays a very important role.Numerous working groups are involved in the related communion, including Inter-Comm.WG IV/III 1 (GIS Fundamentals and Spatial Databases), Inter-Comm.WG IV/III 2 (Integration of image analysis and GIS), WG II/2 (Software and Modeling Aspects of Integrated), WG IV/(Database Design and Spatial data access), WG IV/3 (Temporal Aspects and Topographic database Maintenance), etc.The International Geographer Union (IGU) Study Group on Geographical Information Sciences also takes part in the study.Several international symposia have been held in this study field since 1994, including: (1)International Conference on "Advanced Geographic Data Modeling-Spatial Data Modeling and Query Languages for 2-D and 3-D Application" held in the Netherlands, 1994; (2) International Conference on "Towards 3D, Temporal and Dynamic Spatial Data Modeling and Analysis" held in Wuhan, China, 1995;(3)International Conference on "Advances in GIS Research-7th International Symposium on Spatial Data Handling" held in Delft, the Netherlands, 1996; (4)International Workshop on "Dynamic and Multi-Dimensional GIS" held in Hong Kong, 1997; (5)International Workshop on "Urban 3D/Multi-Media Mapping" help in Tokyo, Japan, 1999; (6)The Second International Workshop on "Dynamic and Multi-Dimensional GIS"(DMGIS'99) held in Beijing, China, 1999.In the DMGIS'99 which was held in Beijing not long ago, more than 160 scientists and experts from 15 countries and regions attended the conference, and 72 papers are presented.Current front-line research topics are extensively discussed and an excellent up-to-date overview on the techniques and technological achievements on dynamical and multi-dimensional GIS were provided. The current research topics in this area include, such as 3-D spatial data modeling, spatio-temporal data model, dynamic handling of spatial data, integrating and inter-operation of heterogeneous data, multi-dimension indexing and querying, visualization of multi-dimension data, interpolation and analysis of multi-dimension data, and large volume of data org anization and database updating. Some achievements made by Chinese scientists and experts were review ed in detail in this paper.The objectives and main tasks of a key project granted by the National Natural Science Foundation of China (NSFC)in 1999 on "development of key concepts and methodologies for dynamic and multi-dimensional spatial data handling" were also introduced in this paper.