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Determining slope stability in a mining operation is an important task. This is especially true when the mine workings are close to a potentially unstable slope. A common technique to determine slope stability is to monitor the small precursory movements, which occur prior to collapse. The "slope stability radar" has been developed to remotely scan a rock slope to continuously monitor the spatial deformation of the face. Using differential radar interferometry, the system can detect deformation movements of a rough wall with sub-millimeter accuracy, and with high spatial and temporal resolution. The effects of atmospheric variations and spurious signals can be reduced via signal processing means. The advantage of radar over other monitoring techniques is that it provides full area coverage without the need for mounted reflectors or equipment on the wall. In addition, the radar waves adequately penetrate through rain, dust and smoke to give reliable measurements, twenty-four hours a day. The system has been trialed at three open-cut coal mines in Australia, which demonstrated the potential for real-time monitoring of slope stability during active mining operations.

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and Cooperative Research Centre for Sensor Signal and Information Processing Ph: $61 7 3365 3697, Fax: +61 7 3365 3684,Abstract-Spatial filtering to reduce noise is an important process to improve phase measurements in interferometric imaging. Currently these techniques are predominately based on filtering the interferometric phase. However the amplitude, which is ignored or only used to a minimal extent in conventional filtering, holds useful information about the nature of the phase measurement. When combining multilook images, adding the full complex vectors produces a least mean square estimate of the interferometric phase. Utilising this principle, a new spatial filtering technique is introduced. In this technique, a compromise is suggested where the square-root of the interferometric amplitude is taken prior to summing the spatially weighted vectors. To deduce the weights for the filtering function it was necessary to utilise a Monte-Carlo approach, which calculates the filter weights via an iterative minimisation procedure. The main application for this filter is to improve the quality of displacement maps obtained by a ground based interferometric radar system that monitors rock slope movement in a mining environment. For this application high SNR is expected, however, due to speckle, large errors can stdl be present in the image. The filter is designed to reduce these errors. Using simulated data and C-Band ERS images, the new spatial vector filter is shown to produce improved phase measurements compared with conventional filtering techniques.

NM-GPR is a new technique which allows the creation of high performance GPR arrays, with the cost and simplicity of an impulse system and the performance of a stepped frequency system. Radar Portal Systems (RPS) had previously developed a prototype high speed 3D GPR system for road assessment based on this technique. This system demonstrated the effectiveness of this approach, allowing penetration to a depth of 1.2 meters for roads, at a speed of lOOkmlh on 24 channels. Since then, RPS has worked to improve the technique, adding features to improve system performance and allow full channel calibration. As a result, we now have an extra SOdB signal performance in comparison to the previous units, allowing deeper penetration. These new units can also be daisy chained to produce virtually unlimited GPR arrays, while still maintaining full synchronization. This paper describes the features and the performance of these new units.