Earth observation technology applied to mining-related environmental issues

Abstract

The environmental awareness of the global mining industry has increased in recent years, from many standpoints.The use a remote-sensing (or 'earth observation') approach in the investigation of historical mining sites to address such issues as acid mine drainage and subsidence has relied so far on aerial photography. Until recently, satellite imagery has lacked the spatial resolution to compete at the scale of an individual mine or mining district. However, a new generation of satellite and airborne technology offers new opportunities on the basis of data collected both in the optical part of the electromagnetic spectrum (visible, near-infrared and shortwave-infrared) and in the microwave wavelength region. Satellite imagery now offers spatial detail at 1-m ground resolution and, thus, mapping scales down to 1 : 5000. Individual ore trucks are resolvable. Additionally, airborne hyperspectral instruments have a sufficiently high spectral resolution to offer remote operational mapping of secondary surface mineralogy, as surrogates to the mapping of acid drainage-related distributions of polluting heavy metals and indicators of stress in the local vegetation. Radar interferometry from satellites has been shown to detect subsidence in old coal-mining areas in terms of centimetres per month—a quantitative objective approach that complements traditional ground surveying. This development is parallelled by that of aircraft-based precision topographic mapping with laser scanning systems (LIDAR). Such technology can also be applied in estimation of the volume of material removed from open-pits or in detection of morphological change in the surfaces of tailings impoundments. Pre-dawn thermal scanning from aircraft can detect and monitor subsurface fires, identify concealed mine-shafts and map the extent of near-surface workings.The increasing trend to cheaper instrumentation and, therefore, lower costs per square kilometre should encourage a thorough evaluation and validation of these latest-generation tools.