User Oriented Calibration Method for Stonex X300 Terrestrial Laser Scanner

Abstract

Terrestrial laser scanners (TLSs) are 3D imaging systems that provide the most powerful 3D representation and practical solutions for various applications. Hence this is due to effective range measurements, 3D point cloud reliability, and rapid acquisition performance. Stonex X300 TOF scanner delivered better certainty in far-range than in close-range measurements due to the high noise level inherent within the data delivered from Time of Flight (TOF) scanning sensors. However, if these errors are manipulated properly using a valid calibration model, more accurate products can be obtained even from very close-range measurements. Therefore, to fill this gap, this research presents a user-oriented target-based calibration routine to compute the calibration parameters of Stonex X300 TLS. The proposed routine investigates range and angular measurements to mitigate mechanical misalignment error sources of this device. Distance and angular index errors were computed, and environmental error sources were considered for optimal modeling estimation. The approach is based to reference measurements in a close-range environment within a 10-meter distance to user-defined ground truth targets. Experiment results show that the errors in the distance are generally increased following the increase in range distance between the laser device and the targets. However, error variations between laser and reference measurements nearly constant relational to the range value. The index error of the Stonex X300 was computed based on mean measurements and found to be equal to 4.6717 mm. On the other hand, the horizontal angular measurements delivered from the TLS device were found to be more consistent with the reference measurements than with thee vertical angular measurements. However, the vertical angular measurements show more significant variations in particular measures compared to horizontal angular measurements. Following this, the angular error index was computed and found to be equal to 0.07 seconds and 0.13 seconds in horizontal and vertical angular measurements, respectively.

Error Analysis of Stonex X300 Laser Scanner Close-range Measurements

“…It is worth mentioning that the geo-referencing process was applied based on the error-free assumption of the reference target measurements that were obtained from the ES-105 total station device. Furthermore, the empirical approach that was implemented in this research was based on calibrating the Stonex X300 device following the user-oriented routine that was explained in [21].…”

“…Similar to most TOF scanners, The Stonex X300 was found to be more relevant for mid-range measurements than it was in close-range measurements due to its measuring principals (which are based on the pulse-ranging technique -as with most similar scanner devices) [4,20]. Even though this laser device is featured in limited range-analysis studies [21], the available studies have revealed the sufficiency of this device for close-range measurements if the measurements have analyzed and signal-to-noise error impacts that are correctly eliminated. For example, [22] presented a practical study to use the Stonex X300 for structural health monitoring (SHM) in a close-range environment.…”