Author Topic: Galileo, the USian GPS and GLONASS  (Read 3737 times)

Galileo, the USian GPS and GLONASS
« on: October 22, 2011, 12:44:32 am »
Been reading about the launch of the Galileo sats, which will eventually form the third constellation of satellites for navigation. What benefits/advantages are there in having another such constellation?

Freer

woollypigs

  • Mr Peli
    • woollypigs
Re: Galileo, the USian GPS and GLONASS
« Reply #1 on: October 22, 2011, 12:47:05 am »
Not sure but this last lot is European so independent from the US and from what I understand more accurate. But I'm sure that out in house rocket fella would tell us soon. 
http://www.letusbeheard.uk March in London on October 19th and on the 12th Rally 4 Our Rights

andygates

  • Peroxide Viking
Re: Galileo, the USian GPS and GLONASS
« Reply #2 on: October 22, 2011, 10:53:38 am »
GPS and GLONASS have about the same accuracy, because they're about the same tech.  10m, say. 

Galileo aims for accuracy around the single metre level, which is a step change.  (The satellites have even more accurate clocks)  It means you can tell what lane you're in, can use it to steer robots with greater precision, hell, you could track players on a pitch sensibly. 

To we the punter, a multi-system bit of kit can munge the GPS and GLONASS satellites together in its calculations and refine your position more.
It takes blood and guts to be this cool but I'm still just a cliché.
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frankly frankie

  • I kid you not
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Re: Galileo, the USian GPS and GLONASS
« Reply #3 on: October 22, 2011, 06:01:33 pm »
Like this.  The green bars are GPS (except no.37)  and the blue ones are GLONASS.  The ones with a 'D' are EGNOS-corrected.
This is an Etrex 30, supposedly all future Garmins (and probably other makes too) will have this capability.



The 'accuracy' of 3m is a fairly meaningless figure in itself, but serves as a basis for comparison.  This was obviously on high open ground - and it was also facing south which is significant because it allows EGNOS to kick in.  Travelling north on a bike you probably wouldn't get any EGNOS reception in the UK (for which reason I usually have it turned off - the above was just testing out the new GPS).

I have seen this unit show an accuracy of 2m - and that was with far fewer satellites received, but with more of them EGNOS-corrected.  I deduce that EGNOS, where it is available, has more impact on 'accuracy' than sheer numbers of satellites.

Where the extra sats score is in areas of poor reception, but I think unless you are relying on GPS to navigate across London, or through dense woodland off-road (neither of which is a particularly likely scenario) then this is more of a theoretical advantage than an actual one.
"This is a complex subject, with a need for more than one highlighter pen."

LindaG

Re: Galileo, the USian GPS and GLONASS
« Reply #4 on: October 22, 2011, 06:03:08 pm »
It comes into its own when tracking across oceans, apparently.

frankly frankie

  • I kid you not
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Re: Galileo, the USian GPS and GLONASS
« Reply #5 on: October 22, 2011, 06:37:47 pm »
Galileo aims for accuracy around the single metre level, which is a step change.  (The satellites have even more accurate clocks)

But I don't think the current 'leisure' GPS system utilises the full accuracy of the existing clocks.
"This is a complex subject, with a need for more than one highlighter pen."

Re: Galileo, the USian GPS and GLONASS
« Reply #6 on: October 22, 2011, 09:26:47 pm »
Strictly speaking, they're all GPS. The USian one is really Navstar, but nobody calls it that.

There are more in place or on the way.

Beidou, which is Chinese & regional.

Compass or Beidou-2, which is a global Chinese GPS. Several Compass satellites have been launched.

QZSS - Japanese, regional, first satellite launched last year.

India is developing its own regional system, IRNSS.

They don't really want foreigners, e.g. the USAF, to control the navigation systems over & around their territories.

NB. Two of the three Navstar ground antennae & two of the five monitoring stations are on British territory.
"A woman on a bicycle has all the world before her where to choose; she can go where she will, no man hindering." The Type-Writer Girl, 1897

Re: Galileo, the USian GPS and GLONASS
« Reply #7 on: October 22, 2011, 09:38:11 pm »
Where the extra sats score is in areas of poor reception, but I think unless you are relying on GPS to navigate across London, or through dense woodland off-road (neither of which is a particularly likely scenario) then this is more of a theoretical advantage than an actual one.
The highlighted one is quite a likely scenario, as this is prime getting lost territory. Been there, used the GPS.
"A woman on a bicycle has all the world before her where to choose; she can go where she will, no man hindering." The Type-Writer Girl, 1897

border-rider

Re: Galileo, the USian GPS and GLONASS
« Reply #8 on: October 22, 2011, 09:52:14 pm »
Where the extra sats score is in areas of poor reception, but I think unless you are relying on GPS to navigate across London...

I use my GPS for that

frankly frankie

  • I kid you not
    • Fuchsiaphile
Re: Galileo, the USian GPS and GLONASS
« Reply #9 on: October 23, 2011, 01:02:29 pm »
I would suggest that most people who cycle in London know their way already.
"This is a complex subject, with a need for more than one highlighter pen."

Panoramix

  • 50 61 6E 6F 72 61 6D 69 78
  • Suus cuique crepitus bene olet
    • Some routes
Re: Galileo, the USian GPS and GLONASS
« Reply #10 on: October 23, 2011, 02:57:49 pm »
I would suggest that most people who cycle in London know their way already.

I sometimes put my bike on the train and cycle to a meeting (can't stand the tube) and never ever had a problem using my GPS in London. I would struggle to find my destination without GPS.

LittleWheelsandBig

  • Whimsy Rider
Re: Galileo, the USian GPS and GLONASS
« Reply #11 on: October 23, 2011, 02:59:56 pm »
I am not one of the 'most people'. It seems like every ride (except for a couple of 'tram track' regular rides) involves plenty of stops to peer at a GPS/smartphone and U-turns to get back on track.
Wheel meet again, don't know where, don't know when...

Re: Galileo, the USian GPS and GLONASS
« Reply #12 on: October 23, 2011, 04:13:25 pm »

The 'accuracy' of 3m is a fairly meaningless figure in itself, but serves as a basis for comparison.  This was obviously on high open ground - and it was also facing south which is significant because it allows EGNOS to kick in.  Travelling north on a bike you probably wouldn't get any EGNOS reception in the UK (for which reason I usually have it turned off - the above was just testing out the new GPS).

I read this before going out so paid special attention to EGNOS.  I'm at 63.5deg North so way further North than the UK.   I had good Egnos reception travelling north, provided my gizmo could see the Egnos satellite to the SE - SW.  Its hilly here so no EGNOS when there was a hill in the way. A reported "accuracy" of 2m was the best on my Oregon.
I'm not sure if anything is gained by turning EGNOS off, as far as I can see it is just seeking an extra satellite. (33,37 and 39) for me today.

andygates

  • Peroxide Viking
Re: Galileo, the USian GPS and GLONASS
« Reply #13 on: October 23, 2011, 05:32:12 pm »
I would suggest that most people who cycle in London know their way already.

I sometimes put my bike on the train and cycle to a meeting (can't stand the tube) and never ever had a problem using my GPS in London. I would struggle to find my destination without GPS.

All this, +1.  I get map-blind in London -- no proper horizon, you freaks -- and GPS is the difference between happy and sad.  And it works fine.  Really, once you've got a starting lock, you can have pretty crappy reception and still be fine. 
It takes blood and guts to be this cool but I'm still just a cliché.
OpenStreetMap UK & IRL Streetmap & Topo: ravenfamily.org/andyg/maps updates weekly.

frankly frankie

  • I kid you not
    • Fuchsiaphile
Re: Galileo, the USian GPS and GLONASS
« Reply #14 on: October 23, 2011, 06:35:04 pm »
I'm sorry if most people don't like feeling grouped under 'most people' - I forgot I was writing in a cyclists' forum  :P

But Andy's point is my point too - more sats is "more of a theoretical advantage than an actual one".
"This is a complex subject, with a need for more than one highlighter pen."

Re: Galileo, the USian GPS and GLONASS
« Reply #15 on: October 23, 2011, 07:04:33 pm »
GLONASS + GPS receivers are markedly quicker to get an initial fix than GPS-only receivers, and perform better with obstructed sightlines such as in a heavily wooded area or an "urban canyon" of tall buildings. That's simply due to the greater number of satellites available. Power consumption is slightly higher, but the next generation of receivers should be able to intelligently turn on GLONASS reception only when needed.

GLONASS is largely a political project and is in many respects worse than GPS, but Galileo will bring a lot of big advantages.

The core navigation system should be significantly more accurate than GPS or GLONASS, but there will be a paid service available with even greater precision - this will be a boon for surveyors and the like who need precise location data, but also for scientists or digital broadcasters who need an extremely accurate time reference. Galileo will have two-way messaging, which will be a big improvement for emergency tracking devices like SPOT. We should see cheaper, more effective search-and-rescue transponders, possibly even being integrated into standard GPS receivers. Unlike GPS, the system will transmit integrity warning messages if there is a chance that erroneous data is being transmitted; This will be a big improvement for seafarers and aviators, for whom an inaccurate signal is worse than none at all.

I expect to see real benefits from Galileo, but perhaps the biggest of all is that it will be under civilian control. Availability will be based on safety of life, not political or strategic reasons. The emergency services will get access to the jam-resistant Regulated Service, not just military users.

Re: Galileo, the USian GPS and GLONASS
« Reply #16 on: October 23, 2011, 08:51:00 pm »
In addition to advantages mentioned above Galileo is claimed to give better reception at more northern latitudes, and also more satellites should give better coverage in canyons (urban or natural !).
But be aware they will operate on a different frequency to GPS (this was forced on Europe by the USA), so I guess will require new kit :-(

frankly frankie

  • I kid you not
    • Fuchsiaphile
Re: Galileo, the USian GPS and GLONASS
« Reply #17 on: October 24, 2011, 11:35:14 am »
GLONASS is largely a political project and is in many respects worse than GPS, but Galileo will bring a lot of big advantages.

If GLONASS is known to be 'worse' then perhaps it is better to turn it off, to see best accuracy figures.  But then again, maybe satellite availablity is more valuable than the last word in accuracy.

Since a large part of the point of these alternative systems is to achieve independence from the US-run system, it's a bit unfortunate that the new Garmins don't have a 'GLONASS only' menu option.  But maybe not surprising, given that Garmin are an American company.  The question is, whether the new chipsets can actually offer this option, so that, for example, future Memory-map GPS units could offer US-free navigation, I can think of a few yankophobes who would go for that!
"This is a complex subject, with a need for more than one highlighter pen."

Re: Galileo, the USian GPS and GLONASS
« Reply #18 on: October 24, 2011, 08:16:59 pm »
But I don't think the current 'leisure' GPS system utilises the full accuracy of the existing clocks.

Commercial GPS can get to 1m on WAAS/EGNOS, and down to 10cm with (subscription) reference station signals. The bloke that did the demo said that the leisure chipsets (eg SIRF III) didn't handle WAAS/EGNOS properly.

frankly frankie

  • I kid you not
    • Fuchsiaphile
Re: Galileo, the USian GPS and GLONASS
« Reply #19 on: October 25, 2011, 12:17:49 pm »
Prompted by this thread I set out to do some comparisons yesterday - taking the E30, the Vista HCx and (just for interest) the older Legend Cx, first to high open ground and then to the bottom of a steep wooded valley in search of really poor reception conditions.  The latter was a total failure - even under dense canopy and beside a rocky escarpment, none of the GPSs had any trouble maintaining a fix, either stationary or at walking pace.  (And IME, at cycling speeds the GPS generally perform better in forest, than at lower speeds).   I suspect that, this far into autumn, the leaves may be quite dry (even though they still look quite green) and so not giving the testing conditions I was looking for.

So I had to fall back on comparisons indoors, where it's easy to control the amount of sky view but it isn't really quite representative of real-world conditions.

On high open ground, nearly a full hemisphere of sky -
Legend Cx,  9 satellites (ie 8 + EGNOS),  8 marked as EGNOS-corrected,  'accuracy' 6 metres.
Vista HCx,  11 sats (10+1), 10 marked as EGNOS-corrected,  'accuracy' 2 metres.
E30,  17 sats (10+1+6), 10 marked as EGNOS-corrected,  'accuracy' 3 metres.

I would suggest that 'accuracy' can only really be used as a self-reference - different units will probably use different algorithms to calculate this.

On my windowsill - facing north, but still with a very good sky view so nearly a demi-hemisphere, so to speak -
I chose a situation that was marginal for the weakest unit, the Legend Cx -
Legend Cx,  5 satellites (no EGNOS),  'accuracy' 6 metres.
Vista HCx,  9 satellites (no EGNOS),  'accuracy' 3 metres.
E30,  14 sats (8+5, no EGNOS),  'accuracy' 8 metres.

In terms of sensitivity (to GPS sats) the new E30 is a close match for the older 'H' types, in fact from continued observation of both while doing this testing, I'd say slightly better.  Personally I don't see this as necessarily a good thing, but it does make for very fast start-up.

Without switching them off, I then went down to the basement, still facing north, a much more restricted sky view.  Probably not even a hemi-semi-demi-hemisphere  ::-)
I didn't bother to put my lovely old Cx through this torture.
In this photo, the unit on the left has a slight advantage in terms of sky view, though with this particular grouping of satellites I don't think it makes any difference.

Vista HCx,  4 satellites,  'accuracy' 12 metres.
E30,  10 sats (6+4),  'accuracy' 12 metres.  Makes me suspect the 'accuracy' is being computed only from the GPS sats.

(The E30 continues to get a fix anywhere in my house, even in the middle by the chimney breast.)
Note in the picture above, the E30 shows an 'elevation' figure - on this screen this is the 'true' elevation as derived from GPS, not the barometric one - and in this example it's 25m adrift.
"This is a complex subject, with a need for more than one highlighter pen."

Panoramix

  • 50 61 6E 6F 72 61 6D 69 78
  • Suus cuique crepitus bene olet
    • Some routes
Re: Galileo, the USian GPS and GLONASS
« Reply #20 on: October 25, 2011, 12:44:25 pm »
This is interesting, you could also let them run side by side for say 6 hours and then plot the recorded tracks, it would give us a good idea of the real world accuracy.

May be in a shed with a wooden roof as this would simulate a not so good signal without being too onerous.

AndyK

Re: Galileo, the USian GPS and GLONASS
« Reply #21 on: October 25, 2011, 12:49:36 pm »
GPS and GLONASS have about the same accuracy, because they're about the same tech.  10m, say. 

Galileo aims for accuracy around the single metre level, which is a step change.  (The satellites have even more accurate clocks)  It means you can tell what lane you're in, can use it to steer robots with greater precision, hell, you could track players on a pitch sensibly. 

To we the punter, a multi-system bit of kit can munge the GPS and GLONASS satellites together in its calculations and refine your position more.

See if a ball crossed a line..?  :demon:

Re: Galileo, the USian GPS and GLONASS
« Reply #22 on: October 25, 2011, 12:55:48 pm »
This is interesting, you could also let them run side by side for say 6 hours and then plot the recorded tracks, it would give us a good idea of the real world accuracy.

May be in a shed with a wooden roof as this would simulate a not so good signal without being too onerous.

Garmin Forerunner 405 on a bedside table (not on my wrist) of a first floor flat (with a flat above it) recording me asleep:-

http://greenbank.org/misc/sleep.jpg

Red plot is HR, green plot is elevation which has a huge range of values (probably as the satellites come in and out of visibility).
"Yes please" said Squirrel "biscuits are our favourite things."