[LINK] Ffx: 'Farmers ‘crippled’ ... as GPS-guided tractors grind to a halt'

[Bernard Robertson-Dunn]

GPS didn't fail, the GPS enhancing systems known as Satellite-Based 
Augmentation System, at least the one used in NZ, failed.

This is from a post on Reddit:

Few people in these comments understand how Ag GPS systems works. My 
systems track GPS And Glonass satellites. I’m tracking anywhere from 10 
to 20 satellites at a time. The more satellites I can track at a time 
the better. To make the solution accurate enough to be useful for 
farming, a correction service is used. That’s what the malfunctioning 
satellite was passing to the farmers. In the US we have a free 
correction system called WAAS that takes it from meters of accuracy to 
something like six to 12 inches. A paid subscription service will get 
you down to an inch of repeatability. These services are usually 
delivered by satellite because it’s normally the most reliable way. You 
can also deliver them by cell or by radio. Rural areas aren’t known for 
great cell coverage and radios are only capable of shorter distances.

Farmers use this to automatically steer their tractors, tell their 
planters where and when to plant, and turn sections of their sprayer 
booms on and off. They’re also used to log where and what you’ve done 
which is very important for crop management. Equipment is so wide that 
the operator can’t just efficiently freehand it without overlapping. You 
can also work late into the night when you just can’t see anymore. Sub 
meter, sub foot, and sub inch levels of accuracy are amazing technology 
that I’d rather not farm without. I can do it, but it makes for a harder 
less efficient day.

This explains how Real Time Kinematic (RTK) GPS works. 
https://www.fjdynamics.com/blog/12-Why-Is-RTK-Essential-to-Agriculture--

There's more about all this at

https://www.reddit.com/r/technology/comments/12u1ugc/farming_satellite_failure_cripples_farmers_as/

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Regards
brd

Bernard Robertson-Dunn
Canberra Australia
email: brd at iimetro.com.au