October 2023 | GPSAR
We succeeded in detecting metal APM and AVM dummies buried in depths of 5cm and 20cm in a natural soil environment with dry vegetation. All dummy objects had been placed in spring (March 2023) and measurement was performed in September 2023. So, soil density and vegetation could regenerate over more than 4 months after placing the dummies.
Testfield in Portugal
Dummy Objects
Anti personal mine (APM) dummy: Aluminium cylinder diameter 84mm, height 30mm, buried in 5cm depth referred to the top.
Anti vehicular mine (AVM) dummy: Cookie can, diameter 18cm, height 10cm, buried in 20cm depth referred to the top.
In comparison to prior measurements, we were using a double cross-meander flight path. This allows faster flight speed and more area-throughput by one battery set than previous circular flight paths. In the images on the next page planned and recorded flight paths are compared. During the flight, there were strong winds, so that the realized flight path (right picture) deviated pretty much from the planned flight path (first dummy picture). Despite the deviation, no degradation in evaluation results could be observed.
Flight planning with orthophoto in the background.
Realized flight from localizaon data. Shaded orthophoto in the background.
Results
In the result picture above, CFAR-based detected pixel are overlayed on an orthophoto. The color scale (magenta to red) indicates the focussing depth of the detections relative to the surface
estimated from an optical DEM. As the DEM is not very accurate, focusing depths provide no absolute information on buried depth.
The ground truth of the buried objects is marked with the black squares and names of the buried objects. There is only one AVM dummy in the scenery buried in a depth of 20cm. All other objects are metal APM dummies buried in 5cm depth. The image shows, that inside and close to all squares, there are significant strong detections. So, all buried objects could be detected. There are, however, some equally strong detections outside the black squares, which must be regarded as false alarms.
The following two images provide views on reflection intensity for different focusing depths. Only the lower part of the scenery is regarded, as it contains both APM and AVM dummies. The AVM dummy provides a strong response at a lower focusing depth than the APM dummies. Intensities are color coded in dB relative to the maximum of the area observed. The magenta circle in the image indicates the maximum.
Radar intensity for a focus depth of 1cm below estimated ground level. Target responses of the APM (Papm3/4alu) dummies are very concentrated. The target response of the AVM dummy is not visible, at all.
Radar intensity for a focus depth of 10cm below estimated ground levels. The AVM dummy (top left) becomes visible and gives the strongest response.
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