Application Of Digital Photogrammetry And GIS In Virtual City Construction

In recent years, considerable development has occurred in the fields of digital photogrammetry, GIS, as well as the field of Virtual City Construction. This advancement has mainly been possible as a result of increasing computer power, refinements in feature and area based image matching algorithms and the reduction in cost of equipments capable in producing near real-time images in digital format. A major goal of Virtual Reality (VR) however, has been to make the graphics displayed by VR systems so realistic, the equipments less bulky and the control tools also so easy to use so that the user can think he or she is completely in another world. A major limitation however, in the widespread application to digital photogrammetry concerns the small format size of the CCD sensor itself, and consequently a limitation in the number of pixels on the sensor. Much time and effort has therefore been expended in recent times, trying to improve coverage through hardware solutions such as producing imaging sensors with increased number of pixels.This paper gives an overview of the main concepts and application of digital photogrammetry in the extraction of geometric and physical information in digital format into a geo-database. It as well describes the workflow process of the VirtuoZo digital photogrammetric system software as applied to scanned photographs from the XuanWu lake Area in the UNIX environment. It also discusses a case study of the XuanWu Lake area of Nanjing with the utilization of data from digital photogrammetry through GIS into virtual city construction.With respect to the case study, the paper analyses the process of data transfer from the VirtuoZo digital photogrammetry system format to the MultiGen software system format. In the MultiGen system, the digital elevation data (DED) and digital feature data (DFD) are used to generate the terrain and feature characteristics respectively. It also outlines the process of generating buildings in the MultiGen system and as well the phenomenon of texture mapping. In the process of texture mapping, photographs from the project site were taken and placed on the generated buildings for them to look as real as they are on the site. The process of data interoperability whereby data can be created in universal standard format for easy accessibility by all users, irrespective of the kind of system they use, is also mentioned. This paper also describes the process of data integration into the Vega Prime software for simulation in a 3D environment and finally outlines some plausible future developments in virtual reality.