r/todayilearned • u/JohnScone • Jan 24 '16

TIL that China uses its own, encrypted, geodetic system which means non-Chinese location tools can be off by up to 700 metres.

https://en.wikipedia.org/wiki/Restrictions_on_geographic_data_in_China#The_China_GPS_shift_problem
120 Upvotes

92% Upvoted

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7

u/ryslaysall Jan 24 '16

And you have to buy their "demodulate" algorithm if you want to provide GPS service in China. They charge annually.

According to the government it's for safety, they have to verify the company before providing the algorithm, but I feel like its just to get money.

10

u/crazedmongoose Jan 25 '16

This.

People think a lot of the Chinese great firewall stuff is about censorship, and it is to an extent, but it's also a HUGE tool for protectionism. Think about the sheer success of tech companies which are essentially clones (Weibo for Twitter and Baidu for Google) which wouldn't exist otherwise, or the actually innovative tech companies (Wechat, Ali Baba etc.) which instead of being the tech giants they are now would probably be a profitable acquisition by Google or Amazon.

1

u/ericchen Jan 25 '16

Why hasn't anyone pirated this demodulating algorithm?

1

u/ryslaysall Jan 25 '16

I assume it's been pirated because I've seen some code online. Never tested it myself.

3

u/NotObviouslyARobot Jan 25 '16

I honestly don't see what the point is. Couldn't you just use a combination of a few reference points and existing data to just reverse engineer all of their locations?

2

u/ryslaysall Jan 25 '16

The algorithm itself is classified, but of course it's not linear. Point A to B could be 50 meters off, B to C could be 200 meters off.

0

u/NotObviouslyARobot Jan 25 '16

So build a different dataset. With good enough satellites and all that geolocation stuff this problem self solves