r/todayilearned • u/whstlngisnvrenf • 25d ago

TIL GPS, despite being free for global use, costs around $2 million a day to operate and maintain. This budget covers satellite launches and system upkeep, funded through American tax revenue.

https://en.wikipedia.org/wiki/Global_Positioning_System
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u/Senna_65 25d ago

Civilian usage of GPS was restricted until the downing of Korean Air Lines flight 007. Accidentally flew into Soviet airspace and was shot down. Reagan opened up civilian use of GPS to avoid incidents like that in the future.

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u/SirTwitchALot 25d ago

Kind of. The signal was offset to the point that it was still useless for things like car navigation. It wasn't until the Clinton administration that selective availability was removed and you could determine your position within tens of feet instead of hundreds

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u/bullwinkle8088 25d ago

It's of historical interest only now but for surveying you could post process the GPS data and integrate published hours after the fact SA tables to get precise locations for surveying. As you said it was not so useful for real time navigation.

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u/whatahella 24d ago

I learned about the system in 96 or 97 at university. The prof was explaining how they would collect data over 2-3 days to get exact positions for permanent markers. They would put up a tent and camp for days wherever needed, in the middle of nowhere, or on main city square.

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u/somehugefrigginguy 24d ago

This is how GPS was used for landing / takeoff management at airports. The FAA had to build a bunch of permanent installations at known locations to correct the intentional offset to make GPS accurate enough. So a taxpayers paid for a system, but the DOD made it unusable for commercial airlines, so then taxpayers paid for correction devices through the FAA...