The Use of Laser Scanner Data for the Extraction of Building Roof Detail Using Standard Elevation Derived Parameters

3D city modelling is a rapidly growing research area in the field of feature extraction. As the demand for 3D data increases, so does the necessity for higher detail building models. The use of aerial imagery and photogrammetric processing has been dominant in the field of feature extraction for several decades. Recently this dominance has been challenged by laser scanning techniques which offer direct 3D data capture at high resolutions. This paper investigates the use of laser scanning data for roof detail extraction. This has already been considered by Maas and Vosselman (1999) who used data with a sample spacing of more than five points per m. The data set in this paper was created using an Optech Airborne Laser Terrain Mapper 1020 LIDAR sensor with 2.5m point spacing which was interpolated onto a 2m regular grid. The aim of this paper is to explore the extent to which useful roof detail can be extracted using this relatively low resolution LIDAR data. A 2D building outline database was used to define the roof boundaries. The ability of the LIDAR data to extract roof detail was tested using algorithms based on LIDAR elevation and derived slope and aspect parameters. An industrial area and a residential area were selected as test sites. Results show that the LIDAR aspect parameter was the most successful at reconstructing building roofs. Using LIDAR aspect data, the results show a percentage correspondence of derived roof ridges to actual ridges of around 33% for the residential area (86% for the industrial area). The amount of roof detail extracted is greater for the industrial study area due to the simpler, larger roof structures. The report concludes that relatively low resolution laser scanning data can be used to extract roof detail, but that results are only significant for large, simple roof buildings.