Airborne Measured Analytic Signal For Uxo Detection
T. Jeffrey Gamey, James Scott Holladay, Reinhold Mahler · 10th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems · 1997
The Altmark Tank Training Range north of Haldensleben, Germany has been in operation since WWI. Weapons training and testing has included cavalry, cannon, small arms, rail guns, and tank battalions. Current plans are to convert the area to a fully digital combat training facility. Instead of using blank or dummy ordnance, hits will be registered with lasers and computers. Before this can happen, the 25,000 ha must be cleared of old debris. In support of this cleanup operation, Aerodat Inc., in conjunction with IABG of Germany, demonstrated a new high resolution magnetic survey technique involving the measurement of 3-component magnetic gradient data. The survey was conducted in May 1996, and covered 500 ha in two blocks. The nominal line spacing was 10 m, and the average sensor altitude was 7 m. The geologic column consisted of sands over a sedimentary basin. Topographic relief was generally flat with approximately 3 m rolling dunes and occasional man-made features such as fox holes, bunkers, tank traps and reviewing stands. Trees were sparse and short (2-3 metres) due to frequent burn off and tank activity. As such, this site was nearly ideal for low altitude airborne surveying. The geophysical sensors included four Cesium vapour magnetometers in a irregular tetrahedron (Figure 1). The average spacing between sensors was 1.5 metres. Reading from these sensors provided the basis for measuring three components of gradient (G,, G,, G,). The vector sum of the gradients was calculated to create a measured total gradient (G), or analytic signal (AS). A real time differentially corrected Global Positioning System (RT-DGPS) was used to provide navigation and data positioning information. A laser altimeter provided height control, and a multi-antenna GPS unit monitored system attitude.