Meeting Tighter Navigation and Data Qc Requirements for Mec Investigations

Currently, good DGM implementation for MEC can get 1 to 2-ft radii navigational accuracies<br>during production and better during demonstration surveys. The differences between a 1-ft and a 2-ft<br>implementation are the selection of appropriate navigation systems, up-front thought in survey design,<br>and rigorous QC including inspections, audits, and failure analysis.<br>At two sites at the former Seneca Army Depot, where the performance objective was to detect<br>small (down to 20mm) target items, Shaw Environmental (Shaw) used an EM-61MK2 towed array with<br>robotic total station navigation that reliably got close to 1-ft total positional error site-wide. Keys to the<br>implementation included optimization of the form factor (deployment system and geometry) to<br>minimize bounce, pitch, roll, and yaw, software and logger selections to minimize latency issues, and<br>establishment of many QC control points.<br>The volume of DGM production data, QC data, QC assessments, and documentation can be<br>overwhelming. Although fixed calibration site data were good indicators of field data quality, the most<br>time efficient indicators of positional data quality were known location QC points.<br>The operational demands of navigation, logging, and monitoring multiple simultaneous data<br>streams on the equipment operators are a challenge. Audits and failure analysis are performed to ensure<br>compliance with operating procedures and, equally important, to optimize those procedures to minimize<br>the potential for incidental or catastrophic errors.