Radio Imaging
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Radio Imaging
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| Electromagnetic Tomography, also known as Radio Imaging Method (RIM) is a method by which an image of the conductivity distribution of the ground between a transmitting antenna and receiving antenna may be obtained.The method is similar to a medical CT Scan,however our access around the feature of interest is often limited to boreholes or roadways either side of the target.Thus we acquire a 2D image that represents a slice through the target. | ||
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Equipment
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| The RIM equipment is divided into the borehole RIM2 system and the handheld RIM2020 system.This photo shows the RIM2 transmitter probe: | ||
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Both systems contain H field antennas operating at frequencies of 2.5 to 992kHz. The RIM2 system measures both amplitude and phase data by means of a control unit synchronized transmitter and receiver, whilst the RIM2020 system measures only amplitude information.
The RIM2 probes are 4m long and 45mm wide, enabling a wide selection of holes diameters to be surveyed.They are connected to winches via 550m of milspec kevlar reinforced fibre optic cable. The use of fibre optic cable greatly improves the signal to noise ratio and effectively isolates the tools as point source transmitters and receivers. The Queensland and New South Wales Mines Departments certify both the RIM2 and RIM2020 tools Intrinsically Safe. |
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Radio Imaging Theory
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| The transmitted radio signal is absorbed (attenuated) as it propagates through the earth. The signal attenuation is a function of the transmission frequency and the electrical conductivity of the media. By setting up a transmitter at one point and a receiver at another it is possible to measure the signal loss and/or phase change along the path between the two points. By collecting many overlapping raypaths it is possible to invert the attenuation distribution into an image by use of specialised processing software. The diagrams below show how the RIM signal is attenuated. The picture on the right shows typical raypath coverage between 2 boreholes. |
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| A radio signal at a specific frequency travels further through low conductivity media (limestone, coal, potash, meta-sediments, granite) than through materials with high conductivity (shale, mudstone, clay, ore zones etc). Therefore a conductive ore within a resistive host acts as an excellent RIM target. The data are processed using the state of the art Imagewin packed from CMTE in Australia. This package is specifically designed for electromagnetic tomography data and contains algorithms such as weight clamping and central weighting to enhance the tomography dataset. |
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| Applications:
Radio Imaging is used in a wide variety of mine applications.Follow the links to either: |
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Radio Imaging Page
