Significance of Photogrammetry in 3D Visualization and Building Reconstruction

Usman KHAN
GIS Researcher
Monash University-School of Geography & Environmental Science, Australia
ukha1@student.monash.edu.au

Abstract :
Three-dimensional textured urban models are becoming more popular with growing importance in geo-visualization. The word “Geo” exclusively means geographical representation of GIS data in real world coordinate system, which differentiates it from movie world arbitrary coordinate system. For many years, the most challenging issue in spatial sciences has been handling of 3D Geo-Information, which has resulted in development of many software applications.

This paper presents the technical processes in the creation of 3D visualizations of urban environments, using buildings in Central Business District Adelaide, South Australia, as an example. The steps involve the 3D measurement of buildings and other 3D objects using stereo Photogrammetry, the measurement and creation of the 3D surface on which the objects are located, the editing of 3D data and the evaluation of various methods of 3D image construction, from building footprint extrusion to full textural rendering, using terrestrial images of the buildings. The addition of objects such as tress, sign posts, etc to the 3D world is illustrated and the various methods of generating walk or drive-through of the 3D environment is both discussed.

While, the research in 3D GIS was progressing, it soon became a 3D spatial project, utilizing Photogrammetry as a fundamental data collection technique. In this context Photogrammetry is used as both a geometric data-gathering tool and also as a remote sensing tool for information extraction. Field surveying prevailed in obtaining control points utilized in aerial triangulation and block adjustment used for processing of the data. Consequently, with resources and knowledge available from three separate but interlinked fields in spatial sciences, a GIS was created while explicitly concentrating on 3D Geo-Visualization.

The goal of the research was to develop a 3D realistic city model. This was carried out through the creation of footprints, reconstruction of buildings, photo realistic rendering and transformation to perspective fly-through and web based applications with Virtual Reality Modelling Language (VRML). The results of the research contribute to (1) the creation of 3D realistic models (2) updating and managing existing GIS footprints (3) 3D geographical visualization and (4) storing original measurements on commercially available systems. In addition, the project explores Virtual Reality Modelling Language (VRML). Just producing visualization is not enough; it should be ensured that what is being produced is based on results and facts of appropriate information analysis.

The major conclusions of the project were:
„X A 3D Geo-approach for urban object visualization is better than creating simple extruded 2D footprints.
„X Stereo photogrammetry can be effectively used to update current 2D footprints.
„X It is possible to work within a geographical coordinate system rather than an arbitrary coordinate system.
„X Complexity of urban topographic objects presents significant issues for their measurement and rendering
„X Proper orientation and triangulation of faces for purpose of visualization of the model is important. Maintenance of a geographic coordinate system through all of the above steps is highlighted, as the project further research aims to link 3D visualizations with GIS and GPS data.