Authors: Coetsee, S; Greyling, N; Narshai, P


Cite As:
Coetsee, S, Greyling, N & Narshai, P 2021, 'Accumulated movement data and the amplitude dispersion index: a collation alarm', in PM Dight (ed.), SSIM 2021: Second International Slope Stability in Mining, Australian Centre for Geomechanics, Perth, pp. 247-258,

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When the return (amplitude and phase) of the electromagnetic signal transmitted and received by the radar antenna for a specific scatterer for the selected resolution is deemed poor quality, a number of processes are set in motion to inform the user that the data for that point or points have lost integrity in the form of badĀ flags. This may be due to the fact that the scatterer properties have changed sufficiently enough to not be able to provide a strong and stable enough return. The scatterer may have moved significantly in three-dimensional space, or the speed at which the scatterer is moving has met and exceeded the phase limit between consecutive scans. The phase limit is determined by the frequency or wavelength utilised by the system, onsite atmospherics, the scan time and the speed at which the pit slope is deforming. If scatterer points on the pit slope cannot be measured consistently during instability, the ability for the system to alarm, based on user selected movement or velocity thresholds, is compromised. These measurement values are dependent on the correct derivation of the true movement from the full phase shift between consecutive scans. This paper discusses the concept of scatterer identification, tracking and the qualification of the consistency of the phase return for movement data accumulation, in collation with the amplitude dispersion index (ADI) for pit slope monitoring purposes. The collation alarm is a representation of both the accumulated movement up until the point whereby the integrity of the scatterer is flagged, and the ADI for a selected area threshold is compromised. This alarm informs the user that the slope is either deforming considerably from a dimensional perspective, or that the pit slope is in an ambiguous state of movement.

Keywords: scatterer, resolution, ADI, phase limit, slope monitoring

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