
Ghost ships, crop circles, and soft gold: A GPS mystery in Shanghai - yoloswagins
https://www.technologyreview.com/s/614689/ghost-ships-crop-circles-and-soft-gold-a-gps-mystery-in-shanghai/
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Pick-A-Hill2019
There is / was a working solution to this called LORAN-C that is being phased
out. The accuracy isn't all that great (60 ft / 18 metres at best) but can be
used to provide a 'disagree' alert to navigation systems. (
[https://en.wikipedia.org/wiki/LORAN-C#The_future_of_LORAN](https://en.wikipedia.org/wiki/LORAN-C#The_future_of_LORAN)
)

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rbanffy
I'd think the circular pattern comes from slight timing differences (they look
like a regular sine-wave-like oscillation) between the multiple satellites
being spoofed as if the transmitters were not completely in sync.

Disclaimer: it's a guess - this is _NOT_ my expertise.

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Pick-A-Hill2019
A pretty darn good guess rbanffy. The spoofed signal is a 'hacked' re-
transmission of a valid GPS signal rebroadcast by local high powered ground
based stations. The basic concept is that you (via a Sat dish) receive a valid
GPS signal while blasting out a wide band RF signal to mask/overwhelm a local
GPS receiver. 'Splatting' the airwaves and then retransmitting a delayed GPS
signal is enough to flick a location by miles. Being able to decode, alter and
then re-transcribe (including checksums) the GPS data stream to an over
saturated local receiver is .... doable (at a nation state level). The
circular patterns are a rounding of the reflection from three (possibly four)
retransmitting stations.

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basicplus2
perhaps they need to start using something like the Airborne Collision
Avoidance System

[https://en.m.wikipedia.org/wiki/Airborne_collision_avoidance...](https://en.m.wikipedia.org/wiki/Airborne_collision_avoidance_system)

