Three dimensional (3D) mapping has been used widely in the spatial industry as a powerful technique
for rendering artificial objects and their surrounding topography. However, an accurate and effective
3D modelling of complex features e.g. feature rich buildings and trees, is still challenging. The aim of
this study is to develop an efficient framework to obtain a high-accuracy 3D model of urban buildings
using Airborne Laser Scanning (ALS) data and aerial ortho-imagery. First, building outlines and a
digital surface model are extracted from ALS data. Aerial ortho-imagery is then integrated to improve
the accuracy of building outlines. Digital photos of building facades are patched to the 3D model for
texture mapping. The accuracy analysis is conducted by assessing the heights and outlines of extracted
features. As far as the authors know, this is the first accuracy evaluation of constructed 3D models. The
digital surface model (DSM) shows vertical errors of less than 12 cm. Building heights are less accurate
than the DSM, with errors of less than 22 cm. This difference is explained in the paper. In order to
examine the building model more closely, the buildings are classified into three categories: simple
rectangular objects, complex polygons, and curved outlines. The horizontal accuracy of the three
categories ranges from 42 to 64 cm in Easting (1 σ) and 16 to 48 cm in Northing (1 σ). The results show
that the horizontal coordinates of simple rectangular buildings are more accurate than those of complex
polygons or circular-shape buildings. Mean errors and root mean square errors for each category are
presented in the paper. |
