GPS Glitched Across The US by as Much as 33 Feet.

[rcjordan]

' That's significant enough to disrupt precision agriculture and autonomous vehicles, the researchers say.'

https://www.sciencealert.com/gps-glitched-across-the-us-by-as-much-as-33-feet-scientists-have-never-seen-this-before

[ergophobe]

Interesting how we have become dependent on that degree of accuracy.

Prior to 2000, accuracy of civilian GPS was about 100m. Fine if you're lost in the woods and need to get home, but not very good if you're trying to sow your field and not your neighbors'.

When they stopped adding the time delay to throw off civilian GPS, accuracy was still on the order of 10-20m.

I've wondered for some time how it got better so this post made me dig deep, roll up my sleeves and ask Claude.

Answer
- ground stations that allow for correction in systematic errors - that alone gets you to 2-3m accuracy.

- in 2000 there was one civilian signal. Now there are three. "Having two frequencies lets receivers directly measure and cancel out ionospheric delay,"

- lots of software and firmware upgrades.

So the 10-20m figure from 2000 was really just "SA turned off, everything else unchanged." Everything since then — new signals, new satellites, augmentation networks, multi-constellation chips, and smarter receivers — has been incremental engineering improvement layered on top, which is why a modern phone can often place you within 3-5 meters, and specialized equipment can do centimeters.

[rcjordan]

>ground stations

I was told that some big farms here put in their own 'local' gps well over a decade ago.  I know that one of these farms has its own big IT shop. There's one farm that some of the towers are visible from the highway.

I've mentioned before that it is weird seeing 3-4 combines harvesting on a dark, moonless night in fields known to have a number of ditches.

[ergophobe]

My BIL worked in Lidar/GPS mapping for a long while and he said that they would deploy a ground station, then fly over with a plane and get centimeter accuracy.