[HN Gopher] GPS Independence: Japan plans expansion of QZSS netw...
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GPS Independence: Japan plans expansion of QZSS network to 11
satellites
Author : throw0101b
Score : 64 points
Date : 2023-05-13 14:18 UTC (8 hours ago)
(HTM) web link (asia.nikkei.com)
(TXT) w3m dump (asia.nikkei.com)
| nimbius wrote:
| Not to rain on the parade but GPS and glonass already offer
| superior coverage, and chinas beidou constellation blows both of
| these out of the water as well.
|
| Are we looking to add QZSS to phones? Do a lot of phones already
| support it?
| SllX wrote:
| QZSS is supplementary GNSS coverage that can service Japanese
| territory if it needs to.
|
| Only issue with BeiDou is it is controlled by the PRC. QZSS is
| already supported by at least iPhones. Someone else can check
| Android device compatibility.
| nimbius wrote:
| Fascinating, I didn't know this. My "old" oneplus 7 doesn't
| support QZSS or BeiDou :/
| SllX wrote:
| There seems to be a couple of different ways Apple's
| written out the specs for different iPhone years under the
| location section, but going back to the iPhone 12 Pro it
| has read the following:
|
| Built-in GPS, GLONASS, Galileo, QZSS, and BeiDou Digital
| compass Wi-Fi Cellular iBeacon microlocation
|
| Officially, I think all of the non-GPS stuff isn't supposed
| to work inside of the United States (enforced by the
| vendor), but don't quote me on that as I saw someone in a
| different comment chain mentioning that they've received a
| QZSS on their phone in SoCal at some times of the day under
| some conditions; but I think the tact most manufacturers
| take (and this could be a Qualcomm thing too) is if it's
| out there, may as well support it in an omnivorous fashion.
| throw0101b wrote:
| FCC officially allowed Galileo signals to be used in the
| US in 2018:
|
| * https://www.fcc.gov/document/fcc-approves-galileo-
| global-nav...
|
| * https://www.fcc.gov/document/fcc-approves-galileo-
| global-nav...
|
| Of course the actual signal was present in the US, but by
| not 'officially' blessing its use, the FCC reserved the
| right to use those frequencies for other things. By
| giving approval the FCC has basically agreed never to
| itself assign uses to the same frequencies, and folks
| don't have to worry about future conflicts.
| Rebelgecko wrote:
| Phones have already supported QZSS for years. Maybe a decade
| for Nexus phones and 5 years for iPhone.
|
| The constellation is designed to help with some Japan-specific
| problems. Eg Glonass is optimized for polar environments, not
| helpful in Japan. For geopolitical reasons, Japan is also not
| crazy about depending on Russia/China.
|
| GPS assumes you'll usually be able to see a satellite when it's
| at an oblique angle, not helpful in big cities with skyscrapers
| where oblique birds can cause issues with multipath reflections
| and all-around bad signal in urban canyons.
|
| QZSS does it's best to make sure there's always a satellite
| _above_ you, not off by the horizon. It plays nice with GPS and
| has a very precise signal similar to the FAA 's WAAS )
| throw0101b wrote:
| Given the orbit used:
|
| * https://en.wikipedia.org/wiki/Quasi-Zenith_Satellite_System
|
| * https://en.wikipedia.org/wiki/Tundra_orbit
|
| Australia, Indonesia, and Papa New Guinea will also benefit.
| bragr wrote:
| My phone regularly picks up QZSS here in southern California
| for what it's worth. At least at certain times of the day with
| a good western view of the sky.
| trillic wrote:
| How do you know this???
|
| Is there an app for displaying the exact signals your phone's
| GNSS receiver is getting? I've played with cgps and am
| familiar with it on the desktop side but never on mobile.
| Rebelgecko wrote:
| On Android you can read the raw NMEA sentences. Or just use
| an app that parses it out and tells you which
| constellations/augmentation sources are being used
| bragr wrote:
| I've used this app [1] for years. It has some paid features
| you probably don't need or want, but the free version will
| show you all kinds of constellation info.
|
| [1] https://play.google.com/store/apps/details?id=com.chart
| cross...
| astrange wrote:
| It's not likely to benefit unless it's near directly overhead
| afaik. It's hard to use GNSS satellites at those angles, and
| if you have a wide open view then most likely you've got
| better angles to something closer in.
| placesalt wrote:
| comment retracted
| icegreentea2 wrote:
| Dunno who down-voted you - but what environment are you
| operating in? One of the claims for the Japanese system (you
| can see it in its orbital design) is that it specifically
| provides more opportunities for overhead signal coverage,
| increasing reliability/accuracy in mountainous and heavily
| urbanized (ie, skyscraper canyons) terrain.
|
| That all being said, I'm also of the opinion that this is
| more of a defense play. QZSS has the nice property have using
| geosync/geostationary orbits - I'd imagine that makes ASAT
| work a bit harder.
| [deleted]
| throw0101b wrote:
| > _In peacetime, at least_
|
| That's a huge proviso given recent geo-politics (and the
| possible change of that premise may be why Japan is hedging).
|
| * https://news.antiwar.com/2023/04/16/defense-official-
| confirm...
|
| * https://gpsjam.org
|
| See also:
|
| * https://www.zdnet.com/article/criminals-are-using-gps-
| jammer...
| kortilla wrote:
| GPS is shit in Japanese cities because of the angle. Read the
| article on QZSS.
| MichaelZuo wrote:
| The majority of the population in japan just lived with bad
| GPS for the last 2 decades?
| johnwalkr wrote:
| In a place like Ginza or Shinjuku it can be really
| frustrating to navigate using GPS when you exit a station
| and your location is off by 20m and your compass is also
| wrong by 90 degrees (I guess because of all the steel
| buildings). I haven't read up on it in a while but I think
| local augmentation for GPS, including indoors in malls, etc
| will eventually arrive once we figure out how to provide it
| as a public service instead of a bunch of companies
| competing to make a proprietary services that serve
| location-based ads.
| myself248 wrote:
| Isn't that essentially what we landed on with Wigle and
| the various wifi location engines?
| astrange wrote:
| GPS doesn't work in dense cities without specific
| corrections because it reflects off the buildings, which
| means you don't know how long a signal took to get to
| you.
|
| QZSS helps but the receiver still has to be designed for
| this specific situation.
| photonbeam wrote:
| Looking at the picture of the orbit, its a lot wider around
| Australia, is that a benefit given the shape of the country or
| happenstance
| bewaretheirs wrote:
| It's a consequence of the orbit's eccentricity - the perigee
| (low point) in the orbit is to the south. The satellite is
| moving faster around the perigee, and slower near the apogee
| (high point) over Japan.
|
| More info here: https://gssc.esa.int/navipedia/index.php/QZSS
| throw0101b wrote:
| Per that _Navipedia_ article, the Centimeter Level
| Augmentation Service (CLAS) of QZSS also allows for
| ionospheric correction data for the Indian and Pacific
| Oceans, which could be helpful for other GNSS systems:
|
| * https://gssc.esa.int/navipedia/index.php/QZSS#Centimeter_
| Lev...
| shagie wrote:
| It's a version of the tundra orbit (
| https://en.wikipedia.org/wiki/Tundra_orbit )
|
| In https://en.wikipedia.org/wiki/Tundra_orbit#/media/File:Ani
| ma... its the green orbit.
|
| The figure 8 shape can be seen in
| https://commons.wikimedia.org/wiki/File:Qzss-01-120s2.gif
| though it isn't quite as extreme in its eccentricity as
| orbits that are trying to service further north.
|
| The shape is based on what is known as "apogee dwell" - that
| from the ground perspective a satellite at apogee (the
| furthest distance from earth) will be moving the slowest
| compared to the ground view. When the satellite is closer to
| Earth that same velocity will be covering more ground
| distance (there will also be some actual change in velocity
| based on how far down Earth's gravity well it goes in and out
| of, though I haven't done enough orbital mechanics to say
| with certainty). Judging by
| https://en.wikipedia.org/wiki/Quasi-Zenith_Satellite_System
| it changes by about 10% as it gets closer to earth.
|
| The main issue (and you'll see this if you use GPS in a city)
| is that GPS can have difficulty in canyons - either urban or
| natural.
|
| https://www.traffictechnologytoday.com/news/connected-
| vehicl...
|
| You need line of site to GPS in order to get an accurate fix.
| If there's mountain or building in the way, it can have
| difficulty. Japan's cities are susceptible to this.
|
| The QZSS system is designed to have a satellite directly
| overhead of Japan so that when you are in a city there is a
| satellite visible.
|
| > The primary purpose of QZSS is to increase the availability
| of GPS in Japan's numerous urban canyons, where only
| satellites at very high elevation can be seen. A secondary
| function is performance enhancement, increasing the accuracy
| and reliability of GPS derived navigation solutions. The
| Quasi-Zenith Satellites transmit signals compatible with the
| GPS L1C/A signal, as well as the modernized GPS L1C, L2C
| signal and L5 signals.
| [deleted]
| dkjaudyeqooe wrote:
| It's the narrow bit over Japan that is intended, but as it
| happens the orbit tracks closest to the most populated parts
| of Australia, on the coast. The central parts (tan on the
| map) are more or less unpopulated.
| [deleted]
| baybal2 wrote:
| [dead]
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(page generated 2023-05-13 23:02 UTC)