Analysis of the Multipass Approach for Collection and Processing of Mobile Laser Scan Data

Abstract

The standard method in surveying practice for adjusting mobile terrestrial laser scan (MTLS) data to correct for global navigation satellite system (GNSS) positioning errors consists of placing a detailed network of surveyed control targets along the corridor being scanned. Although this approach is easy to understand and implement, it is suboptimal with regard to accuracy, efficiency, and safety. Fortunately, the rapid data acquisition that characterizes MTLS enables the user to quickly obtain repeated independent measurements, providing a simple method to examine potential errors that may be present in an individual pass. These multiple passes can be statistically combined and input with GNSS and inertial measurement unit (IMU) data to allow adjustment of the vehicle trajectory. This paper investigates this new multipass approach (MPA) of collecting and processing MTLS data, which reduces control requirements, resulting in significant improvements in accuracy and economic and safety benefits. In this paper, two case studies using MPA are discussed, and the obtained data are analyzed to demonstrate the effectiveness of the MPA. In one of the case studies, GNSS conditions were poor; in the other case study, GNSS conditions were ideal. From these cases studies, the appropriate intervals for control targets were determined based on the desired level of accuracy. In both cases, the multipass approach was shown to be effective in significantly improving accuracy and reducing the need for dense control target networks.