Hacker News Reader

Comment by ck2 | Hacker News Reader

not just space weather, I am pretty sure the atmosphere is being disturbed by toxic human activity both by accident and on purpose

I've run outside every morning for decades and used Garmin with GPS since 2015, I've never had so much trouble

Garmins finally supports dual-band (L1+L5) and BeiDou on newest models but it's still not enough to compensate, I have to use a Stryd footpod to guarantee accurate distances/speed

btw BeiDou GPS blows away US GPS for number of sats and precision but despite Russia's GPS being legal in US, technically BeiDou is not

* https://warontherocks.com/a-signal-point-of-failure-integrat...

* https://payloadspace.com/gps-faces-growing-competition-from-...

* https://en.wikipedia.org/wiki/BeiDou#GPS_vs._BeiDou_Capabili...

View on HN

For resiliency reasons alone, it's been proposed to allow (stop software-disabling) BeiDou in the US, but the last time this was brought up, the administration ran out of time. It's a shame, because when there is precise coverage, it enables things like lane-level city navigation.

https://warontherocks.com/a-signal-point-of-failure-integrat...

yup that was my first link

but of course this administration is never going allow China-anything like low cost electric cars even if it means saving people a fortune in gas

so hopefully in 2029 it can be looked at again

or maybe Dems will also get the Senate too and can be petitioned if they run out of corruption investigations before 2029

it is critical to explain to everyone who isn't technical that GPS is "read only" and no data is being sent to China via BeiDou (just like it's not sent to Russia's Glonass) because that apparently is some kind of weird misunderstanding

on that same note if they somehow made Starlink into a lower resolution GPS backup I'd even trust that too despite personally being anti-Musk everything

Read only or not, relying on Chinese or Russian gps data for increased accuracy even in civilian increases dependency no? That seems like a bad idea to me. I’ve thought for about 20 years that increasing our dependence on anti democratic regimes was a risk, no matter what the benefits for global development etc. It’s not isolationist to want to only rely on your friends and not enemies. (Which is why Europe needs to disentangle itself from the US as fast as possible).

It decreases dependency on GPS and thus it decreases risk because if there's an attack on a GPS system by an adversary, it's likely that they will not be attacking their own system at the same time. I'd rather have my enemy's open source, perfectly functional clock in my back pocket than be without the time. Enjoying that the competing clock has a sub second display is optional.

If you are relying on it without a graceful fall back then it would be a problem. If you take it as a boost on top of existing capabilities then it is a pure win. In practice it can be hard to parse the two scenarios. People get used to thinking that something is available and it turns out that it was always leverage against them.

Whoops I don't know how I missed that in your links!

The weird part to me is that Glonass was not approved either, yet it's as openly as allowed as Galileo that went through a tedious FCC approval process that was invented later. Grandfathered or not, we're clearly not in a worse place using Russian tech for the last 15 years.

> BeiDou GPS blows away US GPS for number of sats and precision

Both BeiDou and GPS are supposed to be limited to 10m precision for civilians.

But, going down a rabbit hole, I found that BeiDou is way more accurate than 10m--3.6m and 2.6m outside and inside the Asia-Pacific region, respectively [1]. And that's with the most simple algorithm. It goes down to ~2.5m using dual-frequencies to account for atmospheric error.

[1] https://www.nature.com/articles/s41598-022-12012-y

> Both BeiDou and GPS are supposed to be limited to 10m precision for civilians.

Maybe in 1998, but Selective Availability was turned off in 2000, and here in the modern era: https://rtklibexplorer.wordpress.com/2024/04/28/dual-frequen...

Oh interesting, I think I conflated two things; Selective Availability and the military-only bands on GPS. While it's true that access to the military band could improve accuracy with dual-band receivers, consumer devices can use dual-band as well (as your link shows), since there are multiple unencrypted bands from navigation satellites nowadays.

I am not sure how to interpret your link, though. It doesn't measure accuracy on it's own, and doesn't include a number for precision between the two units.

My understanding is that the encrypted military-level GPS is much more robust against jamming and spoofing. There's probably a lot of capabilities we don't know that's classified, too.

That is my understanding as well. But having another band allows for error correction as a side benefit.

Called M-Code.

Has a fascinating history.

https://odimpact.org/case-united-states-opening-gps-data-for...

M-Code is a new encrypted signal that is not fully operational yet. OCX was supposed to enable it.

GPS has always had the P(Y) code, which is an encrypted signal, at a higher chip rate than the C/A code that has been broadcast on L1 forever. The P(Y) code has its own interesting history of (semi-)codeless processing. If the US military is lucky, the history books will close on that by 2030: https://www.gps.gov/codelesssemi-codeless-gps-access-commitm... . (Currently, 21 GPS satellites broadcast L5.)

I think the new US GPS satellites have ability to do a spot beam of increased strength in a region of interest.

There are a couple of points:

The L1 signal had selective availability in the 90s, and it no longer does. SA had the real-world accuracy around 30m in practice; the "up to" 100m rarely happened. Without SA, plain L1 with good skyview (low DOP) gets you around 10m, or down under 5m if WAAS is having a good day.

Availability of multiple civilian bands, and cost-effective dual-band receivers, allows an ionosphere-free (no need for WAAS) solution in the 1-2m range, with a single receiver.

Ubiquity of internet connections makes it trivial to apply RTK correction data without having to set up your own base station, and/or, availability of affordable medium-range data radios makes it easy to set up your own base station. In either case, it's easier to run RTK than ever before, and dual-band RTK gets you down into the low centimeters, limited mostly by how accurately your base station was surveyed-in.

And none of that touches the military signals.

With a base station in a known position you can get to cm resolution with somewhat pricey but decidedly hobbyist-accessible gear: https://www.sparkfun.com/sparkfun-gps-rtk-sma-breakout-zed-f...

It seems that all the device manufacturers (they mention Apple, Samsung, and Google) are using BeiDou anyway. I don't know if that includes Garmin watches, though.

https://www.reuters.com/technology/us-agency-probes-risks-fo...

AGPS also helps if you have cell towers nearby.

This is only to make getting a fix faster - A-GPS downloads the almanac data via the internet (fast, but needs internet) instead of directly from the GPS satellites (slow but works everywhere). It doesn't make it any more accurate.

Reply on news.ycombinator.com