The paper describes two improvements in the available three-dimensional (3D) data mode lUrban Data Model (UDM) with surface and body objects. The advantages of these improvements reduce size of data storage; reduce the time cost of data show and visualizing data more realistic than the original model. | Journal of Science and Technology Volume 48, Issue 4, 2010 pp. 82-90 ADDING TIME AND LEVELS OF DETAIL IN THE BUILDINGS MODEL ANH NGUYEN GIA TUAN ABSTRACT The paper describes two improvements in the available three-dimensional (3D) data modelUrban Data Model (UDM) with surface and body objects. The advantages of these improvements reduce size of data storage; reduce the time cost of data show and visualizing data more realistic than the original model. The paper also added to the model time class to manage historical of changes on the spatial properties of 1D, 2D and 3D object. The levels of detail added to show buildings at four levels from simple to complex. Event class in the model should record the reasons to create changes on the buildings in their evolution. Keywords. 3D, data model, spatio-temporal model. 1. INTRODUCTION The rapid growth in the field of economy and population has led to the speed of rapid urbanization. People wish to apply information technology in management of urban problems and 3D GIS solutions be discussed. Management issues need attention in 3D GIS: traffic management, land management, management of buildings. . . The management of the buildings considered one of the focal issues. One of the keys in 3D GIS applications is data model design. The designed model will affect how to represent the data, store data, access data and analysis data. Characteristic of these models is more structured, more objects than 2D model. The models are classified by the model on surface, the model under the surface, model of the surface. Objects in the model have both non-spatial, spatial attributes. Over time the value of these properties were changing. The changes can be discrete or continuous and evolutionary history should be stored in the full database to serve many purposes. There are two important purposes: knowing the trend for future mobilization of objects and providing information to support human decision-making. 3D urban information systems
