Unexploded ordnance or UXO are potentially dangerous munitions of all sizes that remain buried in the earth from wars – even to this day. Many countries have UXO detection issues, including the UK, Australia, SE Asia, the Middle East and the United States. The real issue with UXO comes when a use is proposed for a site, such as an infrastructure or construction project. Then, the requirement becomes finding the UXO through surveying and performing UXO clearance activities until the site is clear and it is approved for safe use.
Magnetometry locates buried military ordnance by measuring differences in the earth’s magnetic field arising from ferrous content in the target ordnance. In addition, magnetometry can be enhanced by using electromagnetic methods which reflect the object’s metallic conductivity. Both methods are valid and can be used individually or in combination.
The use of magnetometers for UXO detection is predicated upon numerous positive factors:
Disadvantages, such as the effects of surface clutter on magnetic readings and magnetic background in certain geological terrains, may be offset by the positive factors noted above and by the implementation of sound field practices including surface cleaning and test surveys. Each unexploded ordnance survey must be treated individually to optimize the methodologies and results generated from the surveying program.
Magnetometer surveys use both individual sensors and multiple sensors (gradiometers). Individual sensors acquire total field data that may exhibit “characteristic signatures.” Sensors in gradiometer mode (i.e. multiple sensors deployed) record mappable gradients or differences that focus specifically on shallow depths of investigation. They are effectively “tuned” to the near surface in which many UXO are located.
The current interest in magnetic technologies for UXO focuses on the use of single and multiple axis sensors, and integration of magnetic and electromagnetic devices. Integration of magnetic and electromagnetic (EM) sensors is or has been adopted as a standard technique by different groups, and reflects an interest in overcoming the limitations of each technique. Magnetics, for instance, works for detection and mapping of UXO due to its ferrous content but may not operable in areas of highly magnetic geology.
Ultimately, the goal is to have a one-pass system that will enable the resolution of each of the six parameters identified in the next section using both magnetics and EM. The rationale is that integration of magnetics and EM (i.e. data fusion) reinforces interpretations of UXO targets. In addition, data fusion can help in developing maps suitable for regulatory agencies responsible for ensuring that the danger to the public is minimized.
Drone magnetic surveys are the next generation in UXO detection and clearance. GEM’s DRONEmag™ sensor can be used to help determine six key survey parameters — including x and y position, depth, type of UXO, and inclination and declination of the UXO. In addition, a magnetic survey will also show buried infrastructure, such as pipes, that could affect the UXO remediation efforts.
The drone survey is an innovative and advanced approach – enabled by the development of new platforms and GEM’s high sensitivity DRONEmag™. Recent surveys by one of GEM’s clients led to the successful delineation of three potentially hazardous targets that had not been found with previous ground surveys at a facility in the Pacific northwest.
GEM has focused on providing UXO contractors with systems that are effective for walking surveys, vehicular surveys and integration with EM instruments. Many new developments have occurred over the past several years – providing a window of opportunity to take advantage of new technologies from a leading R&D organization.
For vehicular surveys, GEM recently launched the world’s only commercial optically pumped Potassium (K) magnetometer / gradiometer. The K-Mag delivers 20x per second sampling rates, 10x higher sensitivity than cesium, improved gradient tolerance, low heading error and advanced software features.
There are numerous key requirements in UXO detection and characterization, whether performed from the ground or on a drone.
A main requirement is the ability to detect small isolated magnetic signatures (i.e. sensitivity) from background signals. With an extremely low noise floor, GEM’s Potassium magnetometer (K-Mag) was designed especially for the detection of subtle signatures, such as UXO with high sampling rates.
Fast sampling is a need as data must be acquired at very high sample density. The K-Mag samples 20 times per second, making it an ideal sensor for both drone and ground applications.
Built-in ease-of-use and optional memory enhancements ensure that surveys are performed efficiently, and that data acquisition of high quality data is achieved on every survey.
But the real difference is in the data. With the development of new UXO modeling and inversion algorithms, it is increasingly important to have noise-free, high-quality results that preserve the magnetic anomaly “shape” information that assists in locating and characterizing UXO. GEM’s ongoing research and development programs are designed to continuously enhance data quality through implementation of new signal processing algorithms and technologies.
Gradient configurations are often optimal for UXO applications – eliminating diurnal effects and enhancing near surface results. GEM’s magnetometers are based on a “true” gradiometer model where measurements are made simultaneously for highest quality calculation of gradients. The Potassium system can be operated in horizontal survey gradient mode to increase survey efficiency by a factor of two.
In addition, GEM’s magnetometers can be configured with multi-sensors on different platforms (backpack or towed / mounted) as required. This capability further enhances productivity as well as the amount of UXO diagnostic information generated from each survey.
The K-Mag and other series of magnetometers are designed for UXO survey companies who need to become familiar with data acquisition, data dumping via high speed connection, and digital maps and dig charts — for remediation and regulatory compliance — as quickly as possible.
Specific features add to the benefits for each UXO program, include fully georeferenced readings so that all locational information is digital, and it is easy to recover ground positions for removal of UXO. Searches can be random or linear – it is at the operator’s discretion and the project’s objectives. And, at a technical level, GEM’s magnetometers and gradiometers do not suffer from increased noise due to the orientation of the sensor in the earth’s magnetic field. GEM’s sensors are free from these effects in comparison with caesium versions so that the data is cleaner and more reliable. Caesium systems also require recalibration which represents considerable downtime on an unpredictable basis.
And lastly, another element required for UXO is simply “toughness” and ruggedness. GEM’s sensors have been tested in the harshest of conditions globally and perform well in the field as well as being the lightest in the industry.
The tragic situation around the world is that people today continue to be injured from unexploded ordnance left behind from WW1 in France and WW2 in Britain and Germany and many other countries. Unexploded ordnance is a significant problem in Laos and Vietnam resulting from conflict in years past.
In Laos, UXO clearance activities have been sponsored by many organizations and proceed meticulously by foot for UXO detection. In future, perhaps solutions, such as drones with high sensitivity DRONEmag™ magnetometers will be part of the solution – allowing for fast and secure unexploded ordnance detection and clearance.
GEM’s advanced magnetometers offer a variety of benefits for UXO applications including high data quality, enhanced productivity, and the ability to effectively detect UXO and phenomena that may affect UXO remediation efforts, such as buried drums or underground storage tanks.
Acquisition of high-quality magnetic results is one of the crucial components of a well-managed UXO remediation project; advances in UAV lightweight magnetometers span a whole new field for cost effective and safe UXO detection.
For UXO applications, GEM’s knowledgeable staff are available for a callback so that we can match your requirements exactly. For a Callback, please click here and we’ll be back to you soon.BACK
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