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OT: OT: China switches off AIS

Started by Jan Panteltje November 24, 2021
On a sunny day (Wed, 24 Nov 2021 12:45:03 -0800 (PST)) it happened Ed Lee
<edward.ming.lee@gmail.com> wrote in
<b8d38d78-8c08-4e34-b4e2-fb5a6c581a02n@googlegroups.com>:

>On Wednesday, November 24, 2021 at 12:39:14 PM UTC-8, Jan Panteltje wrote: >> On a sunny day (Wed, 24 Nov 2021 10:54:54 -0800 (PST)) it happened Ed Lee >> ><edward....@gmail.com> wrote in >> <a76d2909-469b-4829...@googlegroups.com>: >> >On Wednesday, November 24, 2021 at 10:45:07 AM UTC-8, Jan Panteltje wrote: >> >>> On a sunny day (Wed, 24 Nov 2021 06:55:22 -0800 (PST)) it happened Ed Lee >> >>> <edward....@gmail.com> wrote in >> >> <2d1e3950-88b7-4bf8...@googlegroups.com>: >> >> >On Wednesday, November 24, 2021 at 6:31:35 AM UTC-8, Jan Panteltje wrote: >> >>> >> OT: China switches off AIS >> >> >> https://edition.cnn.com/2021/11/24/business/china-shipping-data-mic-intl-hnk/index.html >> >>> >> >> >> >> and not even that, more important: it endagers its own and other vessels >> >>> >> as AIS is used to prevent colisions. >> >> >> So China scores an own goal. >> >> > >> >> >Nop, they have their own version of AIS. They see you, but you don't see >them. You will avoid collision if you pay up the >> >> >insurance premium. >> >> I know they have their own GPS sats >> >> https://en.wikipedia.org/wiki/BeiDou >> >> >> >> But AIS works at 161.975 MHz and 162.025 MHz >> >> https://en.wikipedia.org/wiki/Automatic_identification_system >> > >> >They don't have to follow any standard freq. >> > >> >> Wrote some software for that. >> >> http://panteltje.com/panteltje/xgpspc/index.html >> >> >> >> I am not aware of any other similar system. >> >> Or were you just speculating? >> > >> >Yes, just prudent speculation.
LOOPTHELOOP: >> >> If they had in the RF bands any spectrum analyzer would see it >> >> and decoding would not be such a big thing I'd expect. >> > >> >At the very least, the ships can just report their positions to a central >data center and figure out the mapping. >> That is not so simple, reliable communication from sea to shore and vice versa >over long distances is very hard. >> Even when using satellite, dish aiming or outages when using lower constellations >is an issue. >> The whole idea was to work ship-to-ship on short distances for collision avoidance, >> >basically within the horizon (else earth curvature gets in your way, required >antenna hight then goes up). > >But if you have a big company (China) controlling all their ships, they can >have reliable point to point data links between ships. Including all their >para-military fishing boats, they have a big surface network, not to mention >all the satellites in the sky. GOTO LOOPTHELOOP