This paper focuses on the generation of three dimensional models of large urban/suburban environments. Previous work on the reconstruction of particular environments is based on multiple overlapping aerial or street level images. Unfortunately these approaches do not extend well to large environments. The main reasons for this are that they require expensive high-resolution aerial images and a labour intensive modelling or data capture procedure. Consequently methods have been developed to generate large urban environments based on environmental data such as elevation data or building footprints. This permits the model to be based on actual data for the area being modelled and at a cost far less than that of aerial images. By reducing the data given to the model generation procedure various parameters are undetermined. These include roof style and textured appearance. This paper focuses on the use of building footprint information to construct a three dimensional model. It uses LIDAR data to give the buildings a height value and assigns them a roof using new techniques for roof modelling

a b s t r a c tArchive cartography and archaeologist's sketches are invaluable resources when analysing a historic town or city. A virtual reconstruction of a city provides the user with the ability to navigate and explore an environment which no longer exists to obtain better insight into its design and purpose. However, the process of reconstructing the city from maps depicting features such as building footprints and roads can be labour intensive. In this paper we present techniques to aid in the semi-automatic extraction of building footprints from digital images of archive maps and sketches. Archive maps often exhibit problems in the form of inaccuracies and inconsistencies in scale which can lead to incorrect reconstructions. By aligning archive maps to accurate modern vector data one may reduce these problems. Furthermore, the efficiency of the footprint extraction methods may be improved by aligning either modern vector data or previously extracted footprints, since common elements can be identified between maps of differing time periods and only the difference between the two needs to be extracted. An evaluation of two alignment approaches is presented: using a linear affine transformation and a set of piecewise linear affine transformations.

Particulate deposition experiments were performed in a turbine accelerated deposition facility to examine the effects of flyash particle size and trench configuration on deposits near film cooling holes. Deposition on two bare metal Inconel coupons was studied, with hole spacings (s/d) of 3.4 and 4.5. Two sizes of sub-bituminous coal ash particles were used, with mass mean diameter of 4 and 13 μm, respectively. The effect of a cooling trench at the exit of the cooling holes was also examined in this deposition facility. Experiments were performed at different angles of impaction. Particles were accelerated to a combustor exit flow Mach number of 0.25 and heated to 1183 °C before impinging on a target coupon. The particle loading in the 1-h tests was 160 ppmw. Blowing ratios were varied in these experiments from 0 to 4.0. Particle surface temperature maps were measured using twocolor pyrometry based on RGB signals from a camera. Deposits generated from finer particles were observed to stick to the surface more tenaciously than larger particles. The capture efficiency measured for the small particles was lower than for the larger particles, especially at low blowing ratios. However, the finer particles exhibited a greater variation in deposition pattern as a function of hole spacing than seen with larger particles. The effect of trench configuration on deposition was examined by performing deposition tests with and without the trench for the same hole spacing and blowing ratio. The effects of trench configuration on capture efficiency, deposition pattern, and surface topography are reported. Deposition experiments at impingement angles from 45°to 15°s howed changes in both deposit thickness and temperature. The trench increased cooling effectiveness, but did not change the particulate collection efficiency because the trench acted as a particulate collector.

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Traveling through a single virtual environment only tells part of the story; a particularly interesting aspect is to illustrate how an area has developed over time. This article presents a unified approach to illustrating four-dimensional data concerning a cultural heritage site. The proposed framework provides a semi-automatic approach to both reconstructing the environment and bringing all the time-dependent models into an intuitive visualization package. For each time period considered for reconstruction, the system requires a set of building footprint maps depicting the layout of the environment plus a few statistics. The statistics govern the construction of three-dimensional building models, allowing each building's architectural style, typical building height, and roof style to be altered. This information is automatically processed and converted into a form that can be visualized. By integrating high quality landmark buildings from laser scanning or interactive modelling packages into the automatically generated scene, the cultural heritage site is realized both in a spatial and temporal context. The visualization is achieved via a 4D navigable movie which is presented using two concrete implementations written using Flash and OpenGL. The OpenGL-based implementation allows a collection of 3DS Max scenes to be automatically visualized requiring only a set of camera paths identified by the user.