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Comment by arijun

12 hours ago

> 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

9 comments

arijun

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myself248  12 hours ago

> 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...

  • arijun  11 hours ago

    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.

    • myself248  7 hours ago

      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.

    • hylaride  11 hours ago

      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.

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