InSAR

Ground subsidence, uplift and slow deformation around mines, tailings dams, tunnels, bridges and other infrastructure are hard to track with on-site surveys alone. Geoimage's InSAR service measures this movement from space using Interferometric Synthetic Aperture Radar: two or more radar images of the same area, taken from slightly different positions, are combined into an interferogram whose phase differences show where the surface has moved, and by how much and in which direction.

Geoimage states that vertical movements can be measured to a precision of 1–2 mm, with repeat observations roughly every 11–12 days, so solid surfaces such as bunds, open pits and sparsely vegetated ground, as well as structures such as tunnels and bridges, can be monitored over months and years. Ground resolution depends on the satellite sensor used, from 20 m down to 1 m; Geoimage cites the Sentinel-1 satellites as InSAR-capable radar. Because radar sees through cloud and smoke, day or night, monitoring is not interrupted by weather.

Results are delivered as colour-coded velocity maps in mm/year with secure online access, and Geoimage says processing typically takes about 7–10 days after acquisition. Its published example shows InSAR results over the Cadia mine tailings dam in New South Wales in January and February 2018, a month before the dam wall breach, with subsidence visible along the top of the wall. Geoimage's team supports clients from initial setup through interpretation and analysis of the data.