Airborne LiDAR technology draws increasing interest in
large-scale 3D urban modeling in recent years. 3D Li-
DAR data typically has no texture information. To generate
photo-realistic 3D models, oblique aerial images are
needed for texture mapping, in which the key step is to obtain
accurate registration between aerial images and untextured
3D LiDAR data. We present a robust automatic
registration approach. A novel feature called 3CS is proposed
which is composed of connected line segments. Putative
line segment correspondences are obtained by matching
3CS features detected from both aerial images and 3D Li-
DAR data. Outliers are removed with a two-level RANSAC
algorithm that integrates local and global processing to improve
robustness and efficiency. The approach has been
tested on 2290 aerial images that cover a variety of urban
environments in Oakland and Atlanta areas. Its correct pose
recovery rate is over 98%.