Construction Object Identification from Ladar Scans

Laser Scanning devices (LADAR for Laser Detection and Ranging) are used in construction projects to capture as-built data. They can rapidly generate large unstructured point clouds. This study describes an experiment in which an I-beam on a concrete floor surface is scanned, and the resulting point cloud data used to calculate its pose. Two approaches for segmenting potential target objects are described. Principal axis analysis is used to determine the pose of the I-beam. Bounding boxes are then formed around it and compared to an ideal bounding box generated from the known geometric specifications of the I-beam of interest. A separate laserbased site measurement system (SMS) was used to measure points on the Ibeams to form reference data for estimating the closeness of fit of computed pose of the I-beam to measured pose of the I-beam. Three spheres were used as a means of registering the scan and SMS axes.