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by mannykannot 2828 days ago
GPS is not typically used to confirm a position that is known accurately by other means, and that is not its purpose. Only in those cases where there is a manifest conflict with independent spatial information will the problem be evident.
2 comments
wongarsu 2828 days ago
>GPS is not typically used to confirm a position that is known accurately by other means

I am not so sure about that. The most common use of GPS is in satnav in cars. Satnavs typically show a map, and typically it is very easy to confirm your position on a map. Any inaccuracy by more than the usual few meters would be quickly noticed by the majority of GPS users.

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Rapzid 2828 days ago
People are going to notice a 300m deviation due to landmarks and their eyes.
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mannykannot 2828 days ago
Rarely, if you are navigating at sea or in the air or in the woods... and even on the road, it is not uncommon for my GPS device to be clearly off without justifying the conclusion that there is a fault in a satellite.
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Rapzid 2828 days ago
Here are some users that have a high chance of noticing visually and in aggregate would probably produce a lot of noise:

* Air and sea port operators and navigators

* Military personal running supply lines

* Military personal on foot in operations and training

* Space-X

* NASA

* River boats

* Fresh water fishermen

* Etc

Out of all the possible users who would notice a 300m deviation just based on visual reconciliation, I personally would not say it would be so rare that the USAF would not find out very quickly. Of course, this is ignoring the equipment that would likely detect the issue way before somebody in the Army started phoning the USAF.

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emiliobumachar 2828 days ago
Come on, in urban traffic a 300m error will easily place one in a parallel street.
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gregdunn 2828 days ago
Unless I'm woefully off base here, if the satellites were incorrect, you would basically be permanently 300m off, not just temporarily.

There's not so many GPS satellites out there that you're going to be bouncing around them all the time - even if only one is affected, it would be very noticeable for extended periods of time.

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