Natural hazards such as subsidence, rockfalls and landslides can greatly affect safe travelling. The European Space Agency ESA is now using satellites to monitor hazards across broad areas that could affect road and rail networks.
ESA elaborates: "Traditional monitoring such as photographic mapping to measure changes in the landscape works well for specific locations but is labour intensive and costly. One promising approach is to use maps produced from radar satellites to identify potentially hazardous slopes, followed by repeat monitoring at ground level. By taking regular observations, displacements across large areas can be measured with millimetre accuracy. Any sudden changes in motion indicate a potentially high-risk situation and invite closer scrutiny."