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Survey Capabilities Comparison Chart

Unexploded Ordnance Survey Capabilities

Technology
Description
Capabilities
Limitations
Magnetrometry
Magnetometry locates buried military munitions by detecting irregularities in the earth's magnetic field caused by materials in munitions. This is a completely passive system that emits no electromagnetic (EM) radiation.
1 Can detect larger ferrous objects at deeper depths than EMI methods.
2 Can detect small ferrous objects at or near the surface better than EM sensors with large sensor coils.
3 Multiple systems can be linked together in an array to enhance production rates and increase efficiency.
4 Data can be analysed to estimate target size and depth.
1 Detects only ferrous materials
2 Influenced by high concentrations of surface munitions fragments, background magnetic noise, and site-specific soil properties
3 Commonly used magnetometers are less sensitive than most EM sensors.
4 Instrument response may be affected by nearby power lines and cultural features.
Ground-penetrating radar
GPR systems transmit short pulses of electromagnetic energy into the ground; buried objects reflect the signals back to the receiving unit, where they are recorded and may be processed into an image.
1 GPR responds to both ferrous and nonferrous materials.
2 Multiple systems can be linked together in an array to enhance production rates and increase efficiency.
1 Extremely site specific with minimal applicability to MRSa; generally not recommended for most sites.
2 Performance is severely degraded by conductive and metallic soils.
3 Saturated soils can attenuate signal response.
4 Limited by vegetation and steep terrain.
5 Can be computationally intensive.
6 Susceptible to clutter from a wide variety of sources.
Electromagnetic induction
EMI systems induce an electromagnetic field and measure the response of objects near the sensor. These systems measure the secondary magnetic field induced in metal objects either in the time domain or frequency domain. Conductive objects such as UXO have very different EM properties from soils.
1 Detects both ferrous and nonferrous metallic objects.
2 Advanced systems have multiple frequency and time gates.
3 Additional data can provide information on target shape, orientation, and material properties.
4 Multiple sensors can be linked together in an array to enhance production rates and increase efficiency.
5 EM systems are less susceptible to cultural noise sources, such as utilities, fences, etc. than magnetic methods.
1 Influenced by high concentrations of surface munitions fragments.
2 Limited depth of investigation because the signal falls off with distance - 1/R² vs. 1/R³ for magnetometry. EM radiation may be a hazard around electro sensitive munitions, particularly certain fuses.
3 Limited by vegetation and steep terrain.
4 Although less susceptible to cultural noise, EM systems may still be affected by nearby power lines and cultural features in close proximity to the sensor.
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