To Level or Not to Level: Laser Scanner Inclination Sensor Stability and Application

Abstract

Many modern terrestrial laser scanners (TLSs) are equipped with inclination/tilt sensors—also referred to as level compensators—that can correct out-of-level imperfections in an instrument setup. Some users elect to disable the inclination sensor when their scanner is equipped with one. Those who use an inclination sensor may override its leveling data by linking to external control that defines the level plane. Our case study shows that inclination sensor data can be a valuable quality check for the control data and overall point cloud alignment. Quality inclination sensor data requires careful scan planning. Specifically, laboratory tests indicate that scanner rotation speed influences the reliability of inclination sensor readings recorded during rotation. These inertial effects can be canceled to a limited extent by measuring during both clockwise and counterclockwise rotations. A scan duration within a “stability threshold” can also minimize the inertial effects and variability in inclination sensor readings for scanners continuously measuring inclination data during rotation. Finally, inclination sensor readings from a full 360° rotation are recommended to reduce systematic bias.