Volume 38, Issue 1 (January 2010)
Position Reporting Error of Intelligent Compaction and Continuous Compaction Control Roller-Measured Soil Properties
A field investigation was conducted with four intelligent compaction/continuous compaction control rollers to characterize the spatial reporting of vibratory roller-measured soil properties and to investigate global positioning system (GPS)-based position reporting error. The key reporting characteristics examined include the spatial resolution of roller measurement values (MVs) and the volume/area reflected in each MV. Each vibration-based roller MV investigated is a reflection of soil properties over spatial dimensions that vary across manufacturers. The reporting resolution of roller MVs also varied across manufacturers. Three sources of GPS-determined position error were observed, namely, (1) accuracy of GPS, (2) unaccounted for physical offset of roller-mounted GPS receiver from the drum center, and (3) the spatial averaging of vibration data during roller MV calculation coupled with possible computational latency. The physical offset error was found to be as great as 1.0–2.0 m, while the error due to spatial averaging of vibration data coupled with latency ranged from 0.4 to 0.8 m. Both of these errors are significant but can be estimated and corrected by using a validation procedure described in the paper. Left uncorrected, these errors have a significant adverse effect on the analysis and interpretation of roller MV data when used in quality control/quality assurance specifications.