It is estimated that there are currently the same number of satnav receivers on Earth as there are people. Positioning, navigation and timing signals from space-based constellations such as Galileo and GPS form an invisible, essential infrastructure, underpinning numerous modern aspects of modern life: communications, power and transportation. A new monitoring system developed through an ESA-backed project works like a ‘bodyguard’ for satellite navigation in use at strategic or safety-critical sites. Known as GIDAS, the scalable system immediately detects, identifies and pinpoints satnav interference sources in its vicinity.