MIT Technology Review has an interesting article on a new type of GPS spoofing going on in Shanghai which has the experts puzzled.

Nobody knows who is behind this spoofing, or what its ultimate purpose might be. These ships could be unwilling test subjects for a sophisticated electronic warfare system, or collateral damage in a conflict between environmental criminals and the Chinese state that has already claimed dozens of ships and lives. But one thing is for certain: there is an invisible electronic war over the future of navigation in Shanghai, and GPS is losing.

Strava data makes an appearance as a way of figuring out whether only shipping is affected.

Perhaps bugs or malware in the ships’ AIS or GPS systems were causing the effect? To rule that out, they sought data from another form of transportation completely: cycling.

China has about as many bicycles as the rest of the world combined, with nearly 10 million in Shanghai alone. Some of the city’s cyclists use smartphone fitness apps to track their rides. One in particular, Strava, shares a global heat map of anonymized activities from the previous two years.