apeowl OP t1_j5qj86h wrote
Reply to comment by TWiesengrund in TIL that the European Union developed a satellite navigation system called Galileo, which can provide an accuracy of up to 20 cm (0.7ft) on smartphones, while GPS only reaches around 3 meters (10ft) by apeowl
Yeah, but to achieve (sub-)millimeter accuracy with Galileo you need much less complex technology than for GPS, also Galileo only needs a few minutes for that, while with GPS, such accuracy can only be achieved with long-term measurements.
Also, Galileo's high accuracy service which provides said 20 cm was just released to public today
Volcan_R t1_j5qlbgq wrote
The technology for accurate GPS measurement isn't particularly complex or expensive. You just need a GPS receiver in a fixed location to log the fluctuations against the GPS you are determining the location of. You would use the same strategy for Gallileo I assume but there isn't the intentional addition of innacuracy for non military use.
MrWrock t1_j5rcfvg wrote
In another thread I read that that intentional accuracy drop was removed 20 years ago but there still is a second frequency in the military can use for higher accuracy than consumer grade
Volcan_R t1_j5rmigc wrote
Looks like you're right. I guess the 10-15 foot distortions I was getting 10 years ago when I was working with it were atmospheric distortions from the single frequency.
bdesign7 t1_j5u60bl wrote
Yep. When I was in the Army in the late 90’s/early 00’s we would hold our military gps and a consumer gps (probably a garmin, I would guess) and you could see instantly how much more accurate the military one was.
Shillforbigusername t1_j5rjl7x wrote
Isn’t that additional inaccuracy a thing of the past? I googled it because I was unfamiliar with the concept and came across this:
> Doesn't the government degrade civilian GPS accuracy?
>No. During the 1990s, GPS employed a feature called Selective Availability that intentionally degraded civilian accuracy on a global basis.
>In May 2000, at the direction of President Bill Clinton, the U.S. government ended its use of Selective Availability in order to make GPS more responsive to civil and commercial users worldwide.
>The United States has no intent to ever use Selective Availability again.
bellendhunter t1_j5sng78 wrote
There is indeed a more precise GPS signal for military use. It requires crypto keys to use it. Can’t remember the specifics but I think GPS has a completely separate signal for it.
SupFellar t1_j5qp7hm wrote
"but there isn't the intentional addition of innacuracy for non military use." there is, it's at 20cm
[deleted] t1_j5rliny wrote
[deleted]
ggrieves t1_j5qqi4n wrote
GPS, as I understand it, was intentionally throttled because of concern it could be used to guide a weapon. But technology has improved so much since then that GPS isn't the limitation any more.
seamustheseagull t1_j5txdsg wrote
Nevertheless, I believe GPS devices sold in the US are still required to shut off above a certain speed/altitude, much to the annoyance of amateur rocket/balloon people.
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