To Level or Not to Level: Laser Scanner Inclination Sensor Stability and Application
Publication: Journal of Surveying Engineering
Volume 138, Issue 3
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.
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Acknowledgments
Partial funding for this research was provided through OTREC under Project 2011-398. The writers would like to thank Leica Geosystems and David Evans & Associates for their generous provision of training, equipment, and software to Oregon State University. Maptek Pty donated licenses and support for Maptek I-Site Studio. Riegl Laser Measurement Systems provided their RiVLib API and technical support for the Riegl VZ-400. Shawn Butcher (OSU CCE doctoral student) and Tim Maddux (HWRL) assisted with data collection and background information. We appreciate the time and comments of the anonymous reviewers. Finally, we appreciate the efforts of Gene Roe of lidarnews.com and administrators of laserscanning.uk to distribute an inclination sensor survey. We appreciate those who participated in the survey and shared their unique insights.
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Information & Authors
Information
Published In
Journal of Surveying Engineering
Volume 138 • Issue 3 • August 2012
Pages: 117 - 125
Copyright
© 2012. American Society of Civil Engineers.
History
Received: Apr 7, 2011
Accepted: Nov 17, 2011
Published online: Nov 19, 2011
Published in print: Aug 1, 2012
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