Background
In April 2024, a field in Latvia was identified as a potential site for unexploded ordnance (UXO) contamination. Given its historical significance as part of a World War II battlefield, a detailed survey using SPH Engineering’s UAV-mounted magnetometer system was initiated.
Magnetometers detect variations in the Earth's magnetic field caused by ferrous objects, making them highly effective at identifying buried metallic items. They are used for UXO detection because usually, unexploded ordnance contains metal, allowing the magnetometer to locate it even if it is buried deep underground. A UAV magnetometer survey is particularly advantageous as it is the only approach with zero risk for field personnel, keeping them away from potentially hazardous areas.
Survey Details and Findings
SPH Engineering’s team employed the magnetometer system for scanning the 6-hectare field. The drone was equipped with MagNIMBUS magnetometer, SkyHub and a true terrain-following system. The flight altitude was set to a low clearance of 20 cm between the ground and sensor to provide better detection capabilities. The team conducted the survey over six hours, with the drone flying in parallel lines spaced 1 meter apart.
The survey revealed that the entire field was contaminated with metal objects. Using Geosoft Oasis Montaj software for data processing, over 30 anomalies classified as metal objects of greatest interest were identified.
However, since the farmer was actively cultivating crops in spring, the excavation of the detected anomalies was postponed until autumn.
During the checking of the marked sites in September 2024, a variety of metallic objects were found, including plow teeth and shrapnel, confirming all anomalies detected using magnetometer. Among the findings, a 76 mm World War II artillery shell was discovered at a shallow depth of 30 cm. To ensure safety, the local police were called to excavate and dispose of the artillery shell.
Conclusion
The drone system with the magnetometer became an invaluable tool, enabling the team to safely and quickly survey the field without risking personnel exposure to potential hazards. Its efficiency in detecting anomalies and covering large areas in less time makes it an ideal solution for UXO detection in high-risk environments.
In addition, the discovery of the artillery shell highlights the existing risks posed by remnants of the wartime conflicts. Although the area was considered safe for agricultural use to a certain depth, the presence of UXO underscores the importance of continued monitoring and potential collaboration with authorities for future detection and disposal efforts.
