MINE CLEARING OPERATIONS are traditionally based on the use of metal detectors designed for underground inspections. They are an indispensable detection instrument for personnel engaged in mine clearing operations, which have seen a constant development, especially with regard to sensitivity, ability to operate in mineralised or conductive terrains and in the maintaining of these characteristics over time and under harsh ambient conditions.

Starting from the first decade of this century the diversification of explosive devices used for mining areas, which are often improvised and, for this reason, cannot be foreseen and are even more dangerous, has generated interest in the detection of new types of targets, such as, for example, non-metallic conductive contacts present in pressure plates (carbon rods), cables for remote activation of explosive charges (command wires) and connection conductors between components of a local explosive system (short wires).

CEIA has answered this need with a family of metal detectors, each equipped with specialised multiple sensors, which allow the individual operator to control and signal different types of targets in a selective and unambiguous manner.

CEIA ALIS-RT is a component of this new family which incorporates three detection technologies, which can be used individually or in combination:

• MD :METAL DETECTION
• CRD: CARBON ROD DETECTION
• GPR: GROUND PENETRATING RADAR

ALIS-RT is the Real Time version of the ALIS detector, which has been developed since 2003. ALIS-RT generates real-time alarms on the targets detected, in a similar way to Metal Detector devices, whilst ALIS provides synthetic images, using an Android app and SAR (Synthetic Aperture Radar) processing software designed by ALISys Ltd – Tokyo, Japan.

Triple sensor technology

SENSOR 1 MD

• Low metallic targets
• High metallic targets

SENSOR 2 CRD

• Carbon Rods based IEDs
• Non-Metallic Conductive
• Devices of IEDs
• Short, Single and Multi-Strand Wires

SENSOR 3 GPR

• Dielectric anomalies, soil discontinuities such as: explosive charges, plastic mines, tanks, crates, cavities

ALIS-RT description

The equipment consists of three main parts: an electronic control unit, with an integrated battery compartment, an adjustable two-piece telescopic pole and a compact detection sensor, housing the inductive and high frequency antennas. All the connecting cables between the component parts are installed inside the equipment, to protect against accidental damage.

The electronic control unit is fitted with an operating handle, equipped with an intuitive control keypad and an extremely high contrast transflective display, which is clearly visible even under strong external lighting conditions.

The search head, the inclination of which can be adjusted, is supported by a ball joint in a central position, thereby guaranteeing a high level of stability during detection operations. The equipment has been carefully designed to reduce the weight, thickness and surface area of the sensor, which are usually complex parameters to obtain in a GPR system.

The polymers used guarantee higher mechanical characteristics and dimensional stability over a wide range of operating temperatures and ambient humidity values.

Operating mode

The SUPERVISOR can manage and assign the desired operating mode and the sensitivity of the individual sensor units by means of a setting on the control keypad:

• MD (Metal Detector)
• MD+CRD (Metal Detector & Carbon Rod Detector)
• GPR (Ground Penetrating radar)
• MD+GPR (Metal Detector & Ground Penetrating Radar)
• MD+CRD+GPR (Metal Detector, Carbon Rod Detector & Ground Penetrating Radar)

The intensity of the detection signal is indicated to the OPERATOR visually, by means of a specific bar graph, and acoustically, by means of specific tones for each type of target: metallic, non-metallic conductive, plastic and voids. The acoustic alarms are emitted by an internal loudspeaker, with a high psophometric pressure, or by means of a monaural earphone with a high robustness and a high level sealing. The alarm signalling of the MD sensor is static, with a change of tone when passing above the metallic target, whilst the CRD and GPR signalling are dynamic. The two-tone signalling system allows precision pin-pointing, regardless of the actual operator. The unit is equipped with a comprehensive self-test system.

The ALIS-RT GPR sensor

The GPR sensor offers two special functionalities: TARGET ENHANCEMENT: signalling on anomalies of particular intensity such as cavities or buried insulating containers, becomes static. EXPERT MODE: it provides a display of the GPR target echos in a graph of "depth” Vs “size” on a normalised scale (A-Scan).

The range of the GPR exploration depth can be selected by the operator, by entering the programming menu, using the START Depth and STOP Depth parameters, which identify, respectively, the minimum and maximum depths of interest, or simply by using the control panel, shifting the START and STOP cursors by means of the “Right” and “Left” arrows.

This functionality is particularly useful for concentrating the sensitivity of the GPR on the particular depth of interest and for eliminating the spurious reflections from the ground surface or those due to irregular rocky structures at depth.

The modern digital signal analysis algorithms implemented by the ALIS-RT enable the sensitivity of the MD and CRD section to be optimised even on heavily mineralized and conductive terrains and provide an interpretation of the reflections of the radar signals of the GPR section which automatically determines the acoustic alarm condition and simplifies the use for the operator, who can concentrate exclusively on the visual inspection of the terrain.

In the case of an alarm, the operator can examine the signal by means of the A-Scan (Expert Mode) display, which enables the position, depth and dimension of the target of interest to be estimated.

The GPR physics is not able to determine whether the reflections come from targets made of insulating, conductive or metallic material but cross-referencing with information provided by the MD and CRD sensors enables the situation to be defined and to characterise with greater precision the nature of the detected object.

Integrated GPS

An integrated GPS receiver and a flash memory recording system allow the storage of position data (date, time, latitude and longitude) and detection data (type of target and signal intensity) in real time, during the operations.

Interface capabilities

SERIAL INTERFACEThe serial interface is used for firmware updating operations, for example in the case of modification or implementation of new functionalitiesBT INTERFACEThe Bluetooth interface is used for remote signal reading and maintenance operations assisted by PC.WI-FI INTERFACEThe Wi-Fi interface is used for exporting measurement data towards external processing and display devices, as in the case of the ALIS (ALISys Ltd – Tokyo, Japan) system.

FPK-Setting key

This key allows the programming of the unit only while connected to the detector socket. Once the key is unplugged, the equipment programming is disabled and only a reduced set of parameters can be performed by the operator.

The equipment is supplied by the factory unlocked (full access to programming functions ). After the first use the detector turns once and for all to a dual level mode:

• Operator level, with not allowed or limited programming;
• Supervisor level, having a full access, available only while the setting key is plugged in.

ALIS – DUAL SENSOR MD & GPR DETECTOR WITH SYNTHETIC APERTURE RADAR (SAR)The CEIA ALIS-RT detectors can be converted into ALIS systems by means of a conversion kit available from ALISys Ltd (www.alisys.co.jp).

The most unique feature of ALIS is its visualization function of the metal detector and GPR. Operators can easily identify buried mines on the visualized image. The hand held PC color LCD display provides the survey results both from the metal detector and the GPR as images. The Dual-Tone Metal Detector Audio alert is also available as indication. The dual sensor technology using metal detector and GPR provides discrimination capability of mines from metal clutters. The metal detector and the GPR in this system are supposed to be used as primary and secondary sensors, respectively.

First, the metal detector detects and pinpoints all the objects containing metal pieces, and then the GPR depicts shapes of the objects. Small pieces of metals do not appear in the GPR images, while objects whose size is comparable to mine are visible. Operator can find those shapes in resulting images of the GPR, which are horizontal slices of the underground at different depths, and can compare with the image from the metal detector.