Overcoming the level bubble : terrestrial laser scanning reference frame transformations

Graduation date: 2011Terrestrial Laser Scanning (TLS) is an efficient, effective, and precise measurement tool rapidly growing in popularity in a wide variety of fields. Use of TLS data often requires aligning multiple scans for a more complete model of a scene or object, a procedure known as scan registration. Each scan setup must be transformed (i.e., rotated, scaled, and translated) and adjusted to match the other setups as closely as possible. This research investigates and compares the traditional least squares method against a rapid, noniterative technique recently proposed and develops possible solutions to achieve the strengths of both methods.\ud Additionally, modern TLS instruments are commonly equipped with an inclination sensor to measure deviations from a level setup in order to simplify the registration process. This thesis investigates the reliability, usefulness, and limitations of these sensors. In particular, the concept of a "stability threshold" that ensures reliable inclination measurements in modern, rapid scanners is introduced and sources of inclination sensor error, and procedures to minimize that error, are investigated. While level and unlevel setups appear to produce consistent results, full 360° scan windows measured in both the clockwise and counter-clockwise direction are recommended.\ud Finally, some field applications of TLS reference frame transformations are presented and discussed, including the development of a coordinate system in a large-scale research laboratory and steps toward the development of real-time change detection