3D GIS : current status on perspectives

Abstract

Currently, variety of software (2D GIS, DBMS, 3D CAD) is already capable of handling a wide range of spatial problems, beginning with approaches for describing spatial objects to quite complex analysis and visualisation. However, increasing number of applications (e.g. urban planning, environmental monitoring, telecommunications, utility management) need more advanced tools for representing and analysing the 3D world. Among all types of systems dealing with spatial information, GIS has proven to be the most sophisticated system that operates with the largest scope of objects (spatial and administrative), relationships and means to analyse them. In this context, we believe that the 3D GIS will provide the necessary means demanded by the 3D market. However, what is the status of the 3D GIS? It is the aim of this paper to address some of the issues and problems involved in developing such a system. The development of 3D GIS is not an easy task. Traditionally, GIS maintains information about spatial phenomena and provides means for analysis and thus gain knowledge of the surrounding world. In general, consensus on the demanded functionality of GIS is achieved already years ago. Many authors agreed that it is a type of system able to model, represent, manage, manipulate, analyse and support decisions based upon data associated with real phenomena. 3D GIS has to provide the same functionality as the 2D variant. Nowadays, 2D GISs are common and widely used to handle most of the 2D GIS tasks in a very efficient manner. However, the same kind of systems fail to operate with 3D data if more advanced 3D tasks are demanded. A variety of different software (i.e. 2D GIS, DBMS and CAD) is employed to maintain the objects of interest and extract the required information. Due to deficiency of any of the system to handle 3D objects, the data are spread between several systems. For example, one system is used for data storage and another for 3D visualisation. This situation often faces inconsistency problems, which results in extra time, efforts and money to find the appropriate solution. A significant step toward the development of GIS applications is the agreement on the manner for representing spatial information, i.e. the OpenGIS specifications. The specifications allow increasing number of DBMS to maintain the spatial data together with the administrative data and thus guarantee the consistency. Currently, only the first step is made, i.e. the implementations focus mostly the geometry. Topological representations and operations (especially in 3D) are still only a wish. What are the problems related to development of functional 3D GIS? In this paper, we focus on three major aspects, i.e. Topological model: The design of a 3D topological model is a subject of intensive investigations and several 3D models have already been reported. Each of the models has strong and weak points for representing spatial objects. The consensus on a 3D topological model is not achieved yet. The topological model is closely related to the representation of spatial relationships, which are the fundament of a large group of operations to be performed in GIS, e.g. inclusion, adjacency, equality, direction, intersection, connectivity, and their appropriate description and maintenance is inevitable. Similar to 2D variants, 3D GIS should be capable of performing metric (distance, length, area, volume, etc), logic (intersection, union, difference), generalisation, buffering, network (shortest way) and merging operations. Except metric operations, most of the others require knowledge about spatial relationships. Formalism for detecting spatial