UXO DETECTION

THE METHOD

NAEVA Geophysics has successfully demonsrated that a synthesis of geophysical methods is best suited for ordnance detection. The electromagnetic method (EM) discriminates conductive earth materials from very conductive metallic targets. The magnetic method measures variations in the earth's magnetic field. Localized variations in the magnetic field are magnetic anomalies, caused by subsurface geologic conditions, surface cultural features, or buried ferromagnetic objects. 

NAEVA recognizes that site conditions or cost constraints may prohibit the application of both the electromagnetic and magnetic methods. However, NAEVA's experienced staff can proficiently determine the most appropriate and cost-effective strategy for each site.

EQUIPMENT

NAEVA Geophysics typically relies on two different instrumentations in order to detect buried ordnance. NAEVA employs a Geonics EM-61 metal detector to resolve small shallow features or non-ferrous metallic ordnance, and the Scintrex Smartmag SM-4 total field cesium vapor magnetometer for the detection of larger and deeper ferromagnetic ordnance. The integration of these systems achieves better results than using either of the above applications independently.
DATA PROCESSING AND INTERPRETATION

NAEVA processes and analyzes EM-61 and magnetic data using Geosoft's UXO Analysis system. This software uses analytic signal functions as peak-picking algorithms to determine target location, and Euler deconvolution to aid in determining apparent depth and mass of the buried ferrous and metallic objects. 

In addition, NAEVA utilizes a proprietary computer program, MAGFIT, to yield model fit contours in either plan view or in cross-section.


UXO Targets, EM-61 data
TOP PERFORMER AT JPG

In September of 1996, NAEVA Geophysics participated in the Phase III Advanced Technology Demonstration at Jefferson Proving Grounds in Madison, Indiana to locate and identify unexploded ordnance. Using a synthesis of sensor technologies, NAEVA achieved a percent detection (PD) OF 94%. Furthermore, NAEVA had one of the lowest false alarm rates, 24.8 false alarms per hectare. NAEVA Geophysics attained the overall highest score, achieving the rank of top demonstrator at JPG. Moreover, NAEVA is one of only six companies that have been selected to participate in Phase IV of JPG, which is an endeavor to characterize and discriminate UXO from non-ordnance items. 

Ganged EM-61's employed in UXO detection.