USING DIFFERENTIAL GPS TO DETERMINE RANGE ACCURACY AND PRECISION OF TERRESTRIAL LASER SCANNERS

Building on results and methodology determined during the 2015 NSF-funded Geo-Launchpad (GLP) Internship Program on Terrestrial Laser Scanning (TLS) accuracy and precision range dependency of the RIEGL VZ-400, the 2016 GLP participants tested the efficacy of using differential GPS to determine TLS accuracy. Generally, manufacturers of terrestrial laser scanners only provide accuracy and precision data at a distance of 100m, but field areas scanned for scientific study usually encompass data collected between 0 and 500m, and sometimes beyond 1000m. Researchers must know how precision and accuracy of TLS systems vary with range in order to determine and report rigorous results. The 2015 GLP participants determined that accuracy and precision decreased with range, however an exact trend could not be determined as dusty environmental conditions at the field site created significant degrees of error in some of the measurements. The testing protocol for the 2016 TLS accuracy and precision experiment, seeking to identify an exact trend of accuracy over range, utilized differential GPS measurements capable of sub-centimeter resolution to determine the exact location, in global coordinates, of a target center point at 100m range intervals from 100m to 500m. A comparison of the GPS- determined location and the scanner-determined center points allowed the accuracy of the scanner to be determined. Despite the various environmental and internal sources of error inherent to all TLS surveys, preliminary results suggest GPS can be successfully incorporated to aid in measuring the accuracy of TLS systems.