When he was a fresh-faced doctoral candidate, one of my university professors was involved in the early stages of civilian GPS application.
His work centred on how to utilise this remarkable tech outside the secretive military domain. I remember him telling us about when, one morning in the 1990s, he had woken up to carry out his usual checks and discovered they were all over the place. Overnight the Americans had shifted the constellation (at this time not yet at its full strength of 24 satellites sitting 13,800 miles above us) to focus on the Persian Gulf.
