The study discusses the testing conducted by a SPH Engineering and SENSYS team at the GeoMIL test range using the RadSys Zond Aero 1000MHz NG GPR system. The goal was to assess the viability of GPR as a tool for UXO and landmine detection, considering the specific testing conditions.
GPR is a non-invasive geophysical technique that uses radar pulses to image the subsurface. It emits electromagnetic waves into the ground, and the reflections from subsurface objects are analyzed to create images. This technology has been widely used in various applications, including archeology, utility detection, and environmental assessment. However, its application with UAVs in detecting buried UXOs and landmines has gained attention due to its potential to identify metallic and non-metallic objects in the ground.
The testing occurred at the SENSYS GeoMIL test range, where disarmed UXO, landmines, and scrap objects were deliberately buried. The flight mission was planned and executed using UgCS EXPERT. The data was acquired using RadSys Zond Aero 1000 MHz NG GPR fixed to DJI M300 RTK drone, employing True Terrain Following system with laser altimeter to maintain a fixed flight altitude. SkyHub onboard computer made by SPH Engineering controlled the flight and gathered the necessary data. The survey was completed in three flights with a speed of 1 m/s and a maintained altitude of 0.6 meters. The average flight line separation distance was 0.5 meters.
Of the 45 valid buried targets, 14 were accurately recognized as actual target signals, and their location and depth were previously known. Some of these targets were even detected in multiple profiles, occasionally extending up to one meter beyond the profile.
A noticeable pattern emerged favoring detecting predominantly uniformly shaped targets, such as anti-tank mines and helmets. Oblong targets were generally less detectable, except in certain instances. This observation aligns with the inherent characteristics of the GPR system, which typically performs best when the flight path is perpendicular to the long axis of oblong targets.
The study emphasized the importance of testing conditions in performing Airborne GPR for UXO and landmine detection. The data gathered in ideal conditions allowed for reliable identification and depth estimation of buried objects. The report acknowledged the limitations of the study's conditions and cautioned against assuming similar results in more challenging terrains or heterogeneous soils.
The study highlighted the potential of GPR as a secondary sensor for UXO and landmine detection, mainly when used with magnetometers or electromagnetic induction (EMI) tools. GPR's ability to provide trustworthy estimates of depth and, in some cases, object size positions it as a valuable addition to detection workflows. However, the report stressed that its primary usefulness might be in conditions similar to the testing range – flat land, low vegetation, and uniform soil.
The study provided valuable insights into applying Airborne GPR for UXO and landmine detection. The use of a drone-based GPR system as a stand-alone tool for UXO detection is not recommended; however, using it as an addition to the drone-based magnetometer or EMI system might be beneficial to determine the depth to target, although this requires two separate systems and at least twice the amount of survey time.