G-tek’s geophysicists have up to 30 years experience in the use of various techniques for the interpretation of geophysics data. Much of this experience has been captured in computer software used throughout the company.

Key areas of competency are:

• Removal of geological false alarms from magnetic data;
• Interpretation of UXO data in difficult terrains and environment;
• Modelling of signals from most types of UXO;
• Using a database of signals from a wide variety of objects gathered in many countries to define detection depth in any geological conditions;and
• Interpreting data of poor quality or containing noise from external sources.

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• Advanced data processing using proprietary techniques to interpret the complex information from a SAM survey;
• Removing noise from external sources, such as helicopters and power lines.

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• Use of magnetic, electromagnetic and SAM techniques to identify complex underground networks;
• Detection of pipes where only one end is visible;
• Detection of underground objects in the presence of reinforced concrete slabs and other significant sources of interference;and
• Determining the location of hard and soft rock, igneous intrusions, faults and shear zones to help interpret geotechnical data for highway cuttings and major buildings.

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• Determining the sub-surface geology to identify potential flow paths for contaminants;
• Detection of groundwater levels;
• Detection of burial pits and the extents of landfill;and
• Detection of underground storage tanks

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The major problem in preparing to remediate UXO-contaminated land is the discriminating between UXO and other items of waste, including cultural debris and explosive ordnance waste.

Over more than 20 years, G-tek has developed and extensively tested ways to identify detected objects and decide whether they are likely to be UXO.

By using market-leading discrimination techniques, it is possible to:

• Reduce remediation costs because there is no need to dig individual holes to relocate objects which are not UXO;and
• Safely use earth-moving equipment and sieves to remove the non-UXO waste and fragments, where the removal of all metal debris is required.

G-tek generally uses magnetic detection for discrimination surveys because of the rich amount of information they provide.

G-tek’s surveys operate at extremely high sample rates and can collect very high resolution data, with external noise filtered from the data stream and to extremely high positional accuracy. This allows G-tek’s advanced data processing techniques to identify information that might be included within the noise threshold of other devices.

This provides good detection capability (the ability to find as many objects as possible) and clean signals for discrimination analysis. False signals caused by geology can generally be eliminated without removing a genuine UXO signal interleaved with the signal from the geology.

These high quality signals are then compared with the anticipated UXO types. Theoretical analysis is carried out on each detected object to assess whether it is UXO.

Magnetic data is preferred in all cases where signals from background geology are small or confined to a small number of locations. Whenever geology is a problem, G-tek uses electromagnetic detectors to allow removal of background geology from the digital signal.

Electromagnetics is used to detect non-ferrous metals, because magnetic systems detect only ferrous items.

For quality control, G-tek recommends that customers ‘seed’ the survey area with suspect objects at various depths and orientations consistent with the expected depths for UXO.

All seeded items must be detected as UXO before an area can be passed.

G-tek’s operators, data processors and geophysicists are not made aware of the location, depth or type of the seeded objects, guaranteeing the highest quality discrimination and the lowest chance of UXO being overlooked.

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The two most effective detection technologies are magnetometers and electromagnetic detectors. Each has its own advantages and disadvantages.

With ready access to both magnetic and electromagnetic detectors, G-tek is in the ideal position of being able to use both sensors in any area where the most critical outcome is required.

While the electromagnetic detector will not register geological anomalies and the magnetic detector will not detect non-ferrous metals, the use of both systems ensures ferrous and non-ferrous UXO will be identified with minimal false alarms.

Dual sensor technology often is used for re-locating objects that have been surveyed by a single technology. The use of multiple sensor technology can give an even greater degree of certainty in detection and effective discrimination.

Currently dual sensor technology means two separate surveys, but SAM technology is undergoing US government-sponsored trials for the detection and discrimination of UXO.

Using SAM, magnetic and electromagnetic data are recorded simultaneously and in full registration with the ease of a magnetometer-only survey. This breakthrough will provide a major step forward in G-tek’s detection performance and discrimination capabilities.

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Two issues play an important part in discrimination:

• Detection; and
• False Alarms.

Conventional wisdom suggests that as long as a sufficient number of holes are dug to relocate and identify detected objects, it is possible to claim 100% detection. But it is still possible that a piece of UXO might be deeper than an instrument is capable of detecting. In this case no amount of digging of holes will achieve100% detection.

G-tek’s equipment offers higher levels of detection because of its better signal quality, elimination of noise at source and data gathering techniques that are most appropriate to the equipment, terrain and environment.

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G-tek provides the lowest possible rate of false alarms and the highest possible detection rates.
In controlled tests in the USA, G-tek has achieved False Alarm Rates of 5:1 with detection levels considered to be 100%. Refer to Limestone Hills, Montana.

G-tek is continuing to develop its techniques in this area and is confident that soon it will be able to obtain False Alarm Rates consistently and considerably lower than 5:1.

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