The US Military does use GPS, but ordinary civilians don't have access to high accuracy data. Commercial vendors can license for higher accuracy, but its a hybrid civilian/military system with higher quality data for military use cases.
I think that was previously the case, but not anymore. I can get within a couple meters accuracy on my phone, which is plenty good enough for weapons guidance.
GPS was built by the US military. Its existence was first revealed in Desert Storm back in 1990 when the US military used it to drive tanks into the desert, then come out where and when they wanted. The Iraqis were quite surprised, since they knew that desert, and knew that they would get lost if they tried to do the same maneuver.
Parts of the GPS signal are encrypted to be only useful for the military. The result is that civilian systems an average 4.9 meters of accuracy, while the military is precise to something like a meter instead. But that extra accuracy doesn't help if the signal is jammed.
It was revealed earlier than 1990. In 1983 it was publicly announced that it would be made available for civilian use. Hard to do that without its existence being revealed.
GPS was always intended for both civilian and military purposes, dating back to its inception in the 1970s. In response to the downing of KAL 007 by the Russians in 1983, civilian access to satellite navigation became an explicit guarantee. But that wasn't really an operational turning point, just a clarification of policy.
Before KAL 007, GPS was unaffordable to most users, and not widely developed commercially because there was still uncertainty about whether it would remain available in the long run.
I remember the capability coming as a surprise in 1990, but you're right that Reagan announced that civilian access would happen back in 1983.
Now I don't know if I was misremembering, or if Iraq was simply unaware of the technology, or whether that announcement was for access at some future date.
I do remember discussing GPS on sci.physics in the mid-90s though. Where I learned that GPS is the only commercial technology that has to take general relativity into account. Clocks on Earth run measurably slower than clocks at the altitude of GPS satellites, and the effect is big enough that GPS has to correct for it.
No, very much not. It was an article about how shocked the Iraqis were that the US tanks were able to disappear into the desert, organize, and then assault where and when they wanted to.
Looking back at the history, the tanks began to go into the Saudi desert in August of 1990. They then launched their massive assault on Feb 24, 1991. And caught the Iraqis completely flatfooted. With the tanks moving faster than the news of the tanks for several hours.
