2D and 3D integration |
3D GIS is a relative concept to 2D GIS. 3D indicates the 3D geographic space and the 2D map space based on geographical sphere or ellipsoid. So 3D GIS means the GIS based on the 3D geographic space and the 2D map space which based on geographical sphere or ellipsoid.
3D GIS has advantages in visualization, analysis, and decision making that 2D GIS cannot compete with. 3D GIS can represent the real world without projections. It can represent geographic feature and natural phenomena that 2D GIS cannot represent, in a vivid and intuitive fashion. Therefore it is helpful for making GIS popular among general audience. As for spatial analysis, 3D GIS can not only fully incorporate 2D spatial analysis functions, but also break the limitation of the dull display of spatial information on 2D planes. It is a better alternative for information reading and spatial analysis, and can provide industries with more intuitive assistance in decision making.
However, 2D GIS has been developed since 1960s. Its functions, performance, data, applications, etc., are still popular among old and new GIS users. 2D GIS has simple data models, vast amount of spatial data, abundant mapping functions, various methods for querying, analyzing, and decision making, and mature business application flow. All these merits have determined that, in a long period, 2D GIS will not be completely replaced by 3D GIS which is mainly used for visualization.
Additionally, the retrieval of 3D spatial data is more expensive compared to that for 2D GIS, especially when large 3D scenes are to be modeled. Furthermore, 3D data models are more complicated than 2D data models, making the algorithms for 3D-based spatial queries and analysis functions inefficient. Lastly, 3D GIS has not achieved "real-time" yet due to limitations on network transmission and massive data management.
Considering the advantages of 2D and 3D GIS, people often hope a system has 2D and 3D functions at the same time. In most of the current 3D systems, however, the 3D part and 2D part are independent from each other even they are both included in the system. More specifically, they are separated on data, representation methods, and analysis functions. This has made GIS applications very costly and difficult. The major reason for this problem is that most of the 3D systems nowadays are independent from large mainstream 2D GIS platforms. To solve this problem, 2D GIS and 3D GIS must be integrated from the underlying GIS platform technologies.
When designing the framework, SuperMap UGC added a Realspace technology with 2D and 3D integrated. The 2D and 3D integration technology is designed for developing new generation Realspace GIS software which is integrated with 2D technologies. This software should have capacity to manage massive data as well as powerful analysis functions. This more "GIS" framework design will solve the problems in advanced applications of 3D GIS software. Unlike 2D GIS in which the real space is projected onto a 2D plane for representation and analysis, the 2D and 3D integration technology in SuperMap does not need projections. Instead, it directly loads and displays data in longitude and latitude on a 3D globe, thus provides a real 3d display of the geographical space.
SuperMap 3D focuses on the idea of integrating 2D and 3D, and fully considers the organic integration of the two in terms of both design and specific implementation. More specifically, it has realized: integration of 2D and 3D data, integration of 2D and 3D display, and integration of 2D and 3D service publishing.
Management integrationRealspace adopts the SuperMap SDX+ spatial database technology to store and manage 2D and 3D spatial data in a highly efficient and integrated fashion. The data models and data structures of 2D data and 3D data are integrated. 3D GIS data are compatible with 2D data structures. 2D data have also been adjusted properly so that they can be visualized in 3D scenes with high performance, without the need to convert. The data thus are easier to update and maintain.
With the data integration, Realspace allows for efficiently loading massive 2D data into 3D scenes for display without any conversions. It also supports displaying a snapshot of a 3D model in a 2D window.
As for mapping, Realspace incorporates the 2D thematic mapping functions. Thus it supports making most types of the 2D thematic maps in a 3D scene, such as dot density maps, ranges maps, and label maps, as well as columns and pie charts with 3D effects.
Spatial query and analysis are the basic GIS features. Traditional 2D GIS system is already very mature in terms of those functions, such as buffer analysis, overlay analysis, surface analysis, transportation network analysis, etc. Most of the 3D systems, on the other hand, do not have powerful query and analysis functions due to the lack of support of GIS engines. Many real 3D-based analysis functions have complicated algorithms and low efficiencies, thus are still under development. In this situation, employing 2D-based functions, such as buffer analysis, overlay analysis, network analysis, statistical analysis, etc., in a 3D scene has great practical values.
2D and 3D integration employs spatial analysis and algorithm engines that are integrated with 2D GIS. Most of the query functions (including attribute query and spatial query) and analysis functions of 2D GIS can be used in a 3D system. In the mean time, it also provides some realspace analysis functions such as visibility analysis, flooding analysis, 3D measurements, etc.
SuperMap iServer provides an entire integrated scheme for publishing 2D and 3D services. 2D services are published in the same way as 3D services. The configuration and management are completed with the same methods and interfaces. 2D datasets, 2D maps, as well as the maps' cached 2D and 3D data can be directly loaded into a 3D scene. 2D datasets, maps, and the data in a 3D scene can be saved in the same workspace and published in 3D.