DON’T take your satnav for granted. Existing satellites are ageing, and replacements are behind schedule and over budget, according to from the US Government Accountability Office (GAO).
Satnavs and other GPS devices calculate their position by comparing time signals from at least four satellites. To keep that many within range at all times requires a fleet of at least 24. For now there are 31 operating, but 13 of them are more than four years past their design lifetime.
The first replacement “block IIF” satellites are not due to launch till November, three years behind schedule, and…
