
Galileo, Europe's own satnav, to go online - flexie
http://phys.org/news/2016-12-galileo-europe-satnav-online.html
======
padelt
Remembering the start of it and seeing the US pressuring enough to alter
Galileo to be US-blockable[1] makes me feel old. Really excited though to see
it finally getting usable.

[1]
[https://en.wikipedia.org/wiki/Galileo_(satellite_navigation)...](https://en.wikipedia.org/wiki/Galileo_\(satellite_navigation\)#Tension_with_the_United_States)

~~~
Loic
The cited Wikipedia page links to a wonderful SVG animation[0] comparing the
orbit levels (do we say altitude?) and speed of GPS, GLONASS and Galileo.

[0]:
[https://upload.wikimedia.org/wikipedia/commons/b/b4/Comparis...](https://upload.wikimedia.org/wikipedia/commons/b/b4/Comparison_satellite_navigation_orbits.svg)

~~~
joosters
Is there a reason why GPS has an orbital period exactly half of that of a
geostationary orbit?

~~~
Rebelgecko
It means that the satellite will be in the same place at the same time every
day (give or take about a hundred miles per day of drift)

------
agumonkey
A list of Qualcomm Galileo ready SoC
[https://www.reddit.com/r/Android/comments/5ib1c4/eus_galileo...](https://www.reddit.com/r/Android/comments/5ib1c4/eus_galileo_satellite_navigation_service_will_go/db6wptf/)

------
tinco
How does the paid system work? Do they broadcast more precise data in an
encrypted format?

~~~
Matthias247
It should be the same as with GPS. I can't remember the exact details since my
study is quite some time ago. But in principal GPS (and most likely also
Galileo) works by correlating in the incoming signal with a locally generated
one. The transmitted sequences and basically look like noise in the spectrum.
You can only decode them with their counterparts. For professional (and
military use) other sequences are generated and transmitted in parallel (could
be on other frequencies). These are longer and therefore allow decoding with a
higher precision. But you have to be aware of the code to be able to use those
signals.

There some info written on the web, but for details you need to be aware of
lots of signal theory:

[https://en.wikipedia.org/wiki/GPS_signals](https://en.wikipedia.org/wiki/GPS_signals)

[http://www.navipedia.net/index.php/Correlators](http://www.navipedia.net/index.php/Correlators)

~~~
rconti
I think the assistance provided by DGPS goes down as your distance from the
correction-factor transmitter increases. Likely it's an encrypted message from
the satellites themselves.

~~~
Matthias247
I did not meant DGPS. The satellites themselfes transmit longer sequences for
the "professional" users which allow for a higher precison through the
correlation process.

------
coob
Does anyone know where I can find out more about the tunnel / high rise
compensation mentioned in the article?

~~~
yaantc
From memory, it's likely related to the presence of pilots / reference signals
in the waveform. This helps initial acquisition in bad conditions, and also
helps with multi-path handling (the problem with high rises / urban canyons).
But don't quote me on this, for confirmation you'll have to look for details
on the Galileo signal waveform.

------
rconti
Can anymore more "in the know" explain why an accuracy increase from "several
meters" to 1m would decrease the SAR time from 3 hours to 10 minutes in the
open ocean? It's not like the precision difference matters here. I could see
it helping in the mountains where there's a lot of signal interference so
Galileo might provide better real-world accuracy, but this doesn't make sense
on the open ocean. There must be some other component to the service that's
not being described.

~~~
elevensies
The SAR feature is more than just positioning, I believe it involves the
beacon transmitting to the satellite and the satellite relaying to a ground
station. So it is another feature of the constellation.

A bit more here:
[http://www.navipedia.net/index.php/Galileo_Search_and_Rescue...](http://www.navipedia.net/index.php/Galileo_Search_and_Rescue_Service)
.

------
rihegher
At last! I thought it would never comes through.

------
nraynaud
do you know if the clocks are in sync with the other constellations? can we
use the carriers of 2 constellations at the same time to get an accurate
position?

~~~
Maken
If you have a recent smartphone, it is already using both GPS and GLONASS'
constellations and maybe it's already compatible with Galileo.

~~~
nraynaud
I know, but I'm talking carrier phase data.

------
webjames
Do any consumer phones already have support for Galileo?

~~~
m_eiman
Only two. I suspect next year's models will all have it.

[http://www.usegalileo.eu/EN/inner.html#data=smartphone](http://www.usegalileo.eu/EN/inner.html#data=smartphone)

~~~
mnx
If Snapdragon SoCs have support, could galileo support be enabled by a
software update in phones that have them?

~~~
m_eiman
I don't think there'd be hardware reasons not to, but I'd be surprised if
anyone did that instead of just selling it as a reason to upgrade to a new
phone :P

------
ommunist
I am probably backward thinking, but GPS (sat) and DGPS (land and naval)
combination for precision applications is pretty good. I pinpointed a euro
coin on a closed circuit of several hundred meters with an ordinary Trimble
receiver which accepted DGPS corrections, and it was about 15 years ago. If
Galileo eliminates need of DGPS around the EU, and is more cost-effective, its
fantastic!

UPD: also, I read back then that GPS signal is very accurate, submeter
accuracy locations by default, but signal is artificially roughened, with
clear data available for military use only.

~~~
UncleSlacky
You're thinking of "Selective Availability", whereby a (random walk IIRC) was
added to the signal to deliberately reduce accuracy. It was turned off in 2000
(though it could be turned back on at any time):
[https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_...](https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_Positioning_System#Selective_availability)

~~~
pacificmint
> though it could be turned back on at any time

That's true right now, but the new GPS-III satellites do _not_ have that
feature anymore, so in the future it will not be possible to turn SA on again.
The link you posted explicitly mentions that.

------
PunchTornado
good. can't wait to have it on my phone.

