Airborne Magnetometer Data Reduction and Evaluation at The former Eod Area (Naad 01) Camp Navajo, Northern Arizona

This paper discusses the results of the field activities conducted to evaluate airborne<br>magnetometer data collected over the Former Explosive Ordnance Disposal (EOD) Area (NAAD<br>01) at Camp Navajo, located near Flagstaff, Arizona. Airborne magnetometer data, collected by Oak<br>Ridge National Laboratory (ORNL), was ground validated at selected anomaly locations. The<br>anomalies evaluated were selected based upon sensor height above ground surface (altitude),<br>geology, signal strength, and the ORNL “UXO likeness” model.<br>A land surveyor reacquired the reported location of the selected anomalies in the field. Then,<br>an 8- by 8-meter investigation area was delineated around each selected airborne anomaly location.<br>The grid was re-surveyed with ground-based cesium vapor magnetometer (CVM) and time-domain<br>electromagnetic sensors (EM61). Surface materials were documented and removed and a second<br>survey with both sensors was conducted. Anomalies identified from the ground-based surveys that<br>were considered the most likely cause of the airborne magnetometer anomaly were excavated. Data<br>documented included material density, size, and distance from the declared airborne magnetometer<br>anomaly location.<br>In areas of optimal altitude (below 3.5 meters) and favorable geology (minimal basaltic<br>interferences), there was excellent correlation (>95 percent) between the airborne and the groundbased<br>surveys. In most cases the airborne magnetometer platform was able to detect heavy<br>fragmentation items as small as 10 by 20 centimeters with a positional error of less than 2-meters.<br>Additional evaluations of the ground based CVM and EM61 data, shows similar geophysical<br>response from the regionally predominant basaltic formations.