Factors to be considered when applying atmospheric corrections to prism monitoring measurements: a case study of the Leica GeoMos installation at Orapa Letlhakane and Damtshaa mines [OLDM]

Abstract

When taking measurements for slope stability analysis using prism monitoring systems, there are various measurement errors which could result in incorrect analysis and subsequent reporting and decision making. As measurements are taken across the open pit, rapid fluctuations and spikes in data are introduced due to changes in atmospheric conditions through which the EDM signal travels. The changes in atmospheric conditions across the open pit affects the slope distance measurements to monitoring prisms and adjustments or corrections to the measured distances must be made. The challenge is that the ambient temperature and atmospheric pressure readings used for computing the atmospheric corrections can only be measured at the transfer beacon, and not at the monitoring prism since it is impractical and costly. To achieve optimal prism monitoring results using atmospheric corrections, there are factors which should be considered. These include the suitable position of the meteorological sensor, suitable monitoring times, mitigation of the effect of mining activities and prism monitoring equipment protection. The objective of this research report is to investigate factors which need to be considered when applying atmospheric corrections to prism monitoring measurements. Trial work was carried out to evaluate the method of adjusting slope distance measurements using GNSS generated reference scale factors. This method also has its limitations, however it is a viable option for adjusting slope distances as the open pit becomes wider and deeper. The method of correcting the slope distances using meteorological data is also an acceptable solution, especially when measurements are taken over short distances. This research report should serve as a guide in making decisions for a suitable method for adjusting slope distance measurements for prism monitoring in an open pit mine environment.