How can you pinpoint your location with GPS on your phone without service on the ground, but can’t do the same on an airplane?

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How can you pinpoint your location with GPS on your phone without service on the ground, but can’t do the same on an airplane?

In: Technology

In a purely satellite based GPS, it can take minutes to acquire a signal and position. And this doesnt work well if you’re moving fast. When you’re on the ground, there are many assisted methods of acquiring a GPS signal.

It works in plane too….if you have an unobstructed view of the sky with at least 4 satellites.

Given cramped space and metal ceilinge of typical airliner body this is 50/50 chance of working if you’re in window seat. But if you do it on a private small plane with a big plastic window, it works just fine.

The first issue is the speed you are traveling with, at 250 meters per second the consumerbased hardware and software isn’t suited for this scenario.

The second issue is that you are in the middle of a metal cage, which shields the weak signals from arriving at your receiver.

GPS works by satellites sending a message with a time and location of when the message was sent, your phone can then work out how far away the satellite was when it sent the message by knowing how long it took for the message to get to it. if your phone has a message from 4 or more satellites it can know where it is in 3d space. There is no need for cell service and you can get dedicated GPS devices that have no connectivity abilities.One of the things that the US military (the developers of what most people use for GPS) have put limitations on most domestic GPS chips so that they no longer function when traveling faster than 1,000 knots (1,900 km/h; 1,200 mph) and/or at an altitude higher than 18,000 m (59,000 ft) which would explain why you can’t get a GPS lock on an airplane
Edit: aircraft do not normally reach these speeds and altitude therefore somewhere I have gotten my info wrong, I was told this was why domestic gps might not work on aircraft by a more authoritative source than a random Redditor (although I can’t remember who) and just grabbed the numbers off a [wikipedia page](https://en.wikipedia.org/wiki/Coordinating_Committee_for_Multilateral_Export_Controls#Legacy) believing they were talking about the same thing.

One of the reasons GPS was made available for civilian use is that an airliner was shot down after accidentally wandering into Soviet airspace in the 80’s. So obviously, GPS does work on planes. The reason a phone has trouble has more to do with the lack of sky visibility in the cabin when you’re not at a window seat.