Keywords: digital urban model, scans, information management system.

This paper describes an on-going project with the purpose of building a digital urban landscape, of Gongguan Taipei, for academics and practitioners. Precise urban data around sites are provided and professional practices can use the data to evaluate the environmental impact of new projects. Scans were made of a street and surrounding buildings in the center of Taipei city, based on as-built environmental information. A three-dimensional long-range laser scanner was used to record buildings, plants, and open spaces in a static configuration, as well as the records of pedestrians, vehicles, objects in a dynamic form. As the scan tolerance can be controlled at less than 4 mm/50m, the final urban information management system creates a precise description of objects with colours and textures feasible for internet browsing as well as for infrastructure dimensioning and construction monitoring.

The interaction between designers and environments which used to be studied using design data can now can be made in as-built three-dimensional form. The reality of urban scenes can be reached at a higher level, typically in terms of human figures and trees. The trees in a university campus are presented with more realistic details and shapes than the symbols found in common three-dimensional software. The mass, proportion, and details appear to be the most realistic ever made. Facades and skylines are the major identifiers of a city. Skylines are not only made by roofs, but also the installations on them.

Scan data, in terms of point clouds, were retrieved to represent the as-built geometric information. The digital models were used as the references for chronological comparisons to discover possible configuration changes or construction processes. While the study of the scope was extended from a building, street blocks, to a whole street, the mutual relationship between individual buildings is included to provide a more precise description of the environment for design and planning control. The relationship helps to put together aerial photographs and scan data. The integration is life-cycle-aware and is feasible for future construction reference. With the whole area scanned, the model not only defines a city's appearance, but also makes the data available for code checking.

Compared with photogrammetric modelling, more visual details can be seen with the scanned model. However, the precision level is decreased and building components are less identifiable than the corresponding three-dimensional scanned parts.

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