Unexploded ordnance (UXO) poses a threat to both human life and the environment. Millions of UXO may be located in the United States on active test and training ranges and Formerly Used Defense Sites (FUDS). Essentially, all investigations addressing UXO involve the use of Digital Geophysical Mapping (DGM). A major hindrance to the use of DGM is accurate navigation for sensor position, which becomes especially problematic with ground vegetation and tree canopies. Accurate, inexpensive, and easy-to-use navigation systems of consistent quality are needed for surveys in all terrain and vegetation cover. Navigation accuracy is critical to acquiring the DGM data required for anomaly discrimination. The primary objective of this project was to demonstrate and compare multiple navigation systems to support DGM.
Phase I demonstrations were performed by selected vendors to determine the capabilities of eight innovative navigation systems. The benchmark for comparison was a typical $250 Garmin Global Positioning System (GPS) III handheld. The handheld unit was easy to use, readily available, inexpensive, and much more accurate than expected. Although ill-suited for direct usage to support geophysical mapping navigation, it did provide a benchmark for navigation performance as a less accurate but inexpensive approach. Future efforts in Phases II and III will develop and demonstrate the navigation technologies integrated with typical geophysical equipment such as the electromagnetic (EM)-61 series and G-858 magnetometer sensors, with development toward commercial, integrated system approaches.
The navigation systems were deployed with varying degrees of success. Phase I demonstrations delineated the relative strengths and weaknesses of each system, the areas of application where each system would be beneficial, and the areas where each system required improvement. Following compilation of the results, the most successful technology with the most value for supporting DGM was the Robotic Total Station (RTS) laser navigation as demonstrated by Shaw Environmental & Infrastructure, Inc. It easily can meet all accuracy needs in the open to permit geophysical data analysis for discrimination. In addition, the integration of geophysical equipment was successfully demonstrated. The Arc Second Inc. System, which is also based on laser positioning, matches the RTS performance, but its use was limited greatly by range. The system as it currently exists is perfectly suited to provide highly accurate three-dimensional data acquisitions for small areas where dense geophysical mapping is desired to interrogate specific anomalies.
Navigation in the open and in obstructed wooded areas was less accurate than expected or advertised by vendors. Additional efforts are needed to develop most systems such that they meet desired accuracies in support of geophysical mapping and reacquisition. Where applicable, the line-of-sight laser-based systems had the best performance for the cost. With post-processing adjustment from known monument points, the inexpensive handheld and card-based GPS units provided reasonable accuracy for initial investigations in which a large search radius could be tolerated. (Project Completed - 2004)