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EGNOS declared operational


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At last EGNOS is actually officially "switched on" to give Europe the equivalent systems to the US's WAAS

 

"Ongoing monitoring of the augmentation signal shows it improves the accuracy of GPS to within one to two meters and is available more than 99 percent of the time."

 

see

http://www.insidegnss.com/node/1652

 

and

http://www.gpsworld.com/gnss-system/galile...en-service-8972

 

I've had it switched on my Garmin eTrex Vista HCx for a while and it usually reports an accuracy of about 2m.

 

Anyone noticed an improvement in accuracy (assuming you have GPSr that support EGNOS of course!) ?

 

Magpie Guy

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Being well fick how do I know if I am receiving an EGNOS signal, or the American signals? and how do I switch from one to the other or does my GPS decide?

Egnos augments the (US) GPS satellite signals. On my garmin you select DGPS (differential GPS) or some such in the settings and when it's receiving them then the signal bars have a little D in them. You need a clear view of the southern sky to get it.

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how do I know if I am receiving an EGNOS signal, or the American signals? and how do I switch from one to the other or does my GPS decide?

 

It depends on your specific GPSr - I can only speak regards my Garmin Etrex Vista HCx:

 

Main Menu -> Setup -> System -> WASS/EGNOS = Enabled (think you also need to set GPS = Normal too).

 

To check accuracy

Main Menu -> Satellite and in the top Location shows +/- x meters/feet

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As far as I am aware, EGNOS (Europe) and WAAS (USA) are the same where a gps receiver is concerned.

 

I also understood that EGNOS was turned on a few years ago, for testing purposes.

 

I know my Garmin 60CSX has been showing the 'D' for WAAS on the satellite page for as long as I have had it (approx 18 months), and my Vista before that could receive the enhanced signal.

 

Ivan

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I have had the little D's for years as I always had WAAS turned on, I just wondered it there was a way to switch from the US to the European systems, but reading ivanidea's posting it seems the GPS sorts itself out. I have noticed the D's seem to be displayed a lot more these days so maybe I am benefitting. Although I still keep posting the odd DNF :drama:

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how do I know if I am receiving an EGNOS signal, or the American signals? and how do I switch from one to the other or does my GPS decide?

 

It depends on your specific GPSr - I can only speak regards my Garmin Etrex Vista HCx:

 

Main Menu -> Setup -> System -> WASS/EGNOS = Enabled (think you also need to set GPS = Normal too).

 

To check accuracy

Main Menu -> Satellite and in the top Location shows +/- x meters/feet

 

Thanks for that!

I've just switched it on, on my Vista......... Looking forward to see if it makes any difference!

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EGNOS has indeed been working for quite a while now. What they've now done is to certifiy the signal is accurate for 'safety of life'. Previously if you got lost at sea died and blamed the signal they'd have said sorry but not our fault we've not certified it!!

 

If you want to know how it works, where the satelites are (RIMS and so on) then have a look at my resource website at www.follow-the-arrow.co.uk where I've put some technical information in a non-technical about GPS accuracy, EGNOS and so on.

 

Differntial GPS (DGPS) is slightly different and requires a ground base station broadcasting a signal that the GPS picks up. You need a DGPS receiver to get the signal to pass it to the GPS. With EGNOS the GPS picks up the corrected signal directly from the geo-stationary satellites.

 

Chris (MrB)

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I just wondered it there was a way to switch from the US to the European systems
The EGNOS and WAAS satellites are geo-stationary (i.e. in a much higher orbit than the GPS satellites) so your GPSr should choose the one that is appropriate to the location. With the eTrex I don't think there is any way to know which one it decides to use.

 

Rgds, Andy

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... With EGNOS the GPS picks up the corrected signal directly from the geo-stationary satellites.
That could be misinterpreted - though the EGNOS satellites broadcast a ranging signal, that's not enough to give you a location and you still have to pick up the ordinary signals from GPS satellites just as before. What EGNOS does is broadcast corrections to the satellite data and information about the atmosphere so that the receiver can fine tune the information from the regular GPS satellites.

 

While the corrections allow it the improve accuracy when everything is working correctly, EGNOS also lets the receiver know if a satellite has lost the plot completely. This function is intended to avoid gross errors in a fault situation and is subtly different to increasing accuracy in a fully working condition. I think this aspect is probably the more important in many critical applications, whereas the fine tuning of a fully working system is more significant to us.

 

It's also important to remember that the figures they quote are for perfect reception such as you would expect standing on top of a tor on Dartmoor, and any obstructions, reflections and so on mean in most situations we won't see that level of accuracy. I do see an improvement with EGNOS, but mostly it's not as dramatic as the published figures suggest.

 

Rgds, Andy

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Hi All

I had a look at the settings on my Oregon and the "Select GPS Mode" only allows for "normal""WAAS"or "Demo Mode"

so my question is, is WAAS mode the same as EGNOS?

or will there be an update to the firmware somewhen?

i ask because as yet i have not seen the "D"

hope this is not a silly question :lol:

 

Yes, EGNOS is the same as WAAS (as far as your GPSr is concerned) - they're both the same method of receiving differential corrections, but in different geographic areas. I think there's another one planned for the Pacific area, but don't know what it's called.

 

Because the satellite is in geosynchronous orbit, it is over the equator, so your GPSr may not 'see' it depending on your sky view. When you are receiving it, the satellite view will show Ds in the signal bars.

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Isn't that a bit like Advocaat? :lol:

 

Joking aside, won't it just reduce the margin of error, rather than the actual accuracy? I've found caches on a limestone pavement near hear where there's thousands of potential hiding places in all the grykes in a 10 foot radius, but I've always been taken to the correct place within inches, despite the margin of error being a lot bigger than that. What it'll do is improve the confidence that the position is correct, rather than necessarily improve the actual accuracy.

 

Well, that waffle makes sense to me. :)

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The 3 EGNOS/WAAS satellites we can pick up in the UK (Artemis 37, Inmarsat Indian Ocean West 39 and Inmarsat Atlantic Ocean East 33) are quite low on the horizon, typically only some 20 to 30 degrees high. This means if you have a hill, trees or buildings on your south eastern, southern or south western horizon you may not pick up the corrected signal and thus not see the D's in the display.

You can see a map of the satellite coverage here.

 

Chris (MrB)

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Quite excited when I read this so decided to give it a go. I left my Oregon 400 on top of my tower above everything for miles, completely clear view of sky. Enabled WAAS but didn't get any D and no better than the usual 6m I get in such good conditions.

 

Is the system on permanently?

 

Any other suggestions?

 

Ta

 

Paul

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Quite excited when I read this so decided to give it a go. I left my Oregon 400 on top of my tower above everything for miles, completely clear view of sky. Enabled WAAS but didn't get any D and no better than the usual 6m I get in such good conditions.

 

Is the system on permanently?

 

Any other suggestions?

 

Ta

 

Paul

 

If you've just switched it on it can take 20 minutes sometimes to download the information from the EGNOS satellites before the D's appear.

 

Chris

Graculus - Volunteer UK Reviewer

Resource website for UK and Ireland Geoacachers - www.follow-the-arrow.co.uk

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If you own a 60CSx or one of the variants and are running software version 3.90 then you sould be aware that there is now a new version 4.00 available that, amongst other things

QUOTE from Garmin:-

 

Fixed WAAS information not showing 'D' in satellite bars. Error was introduced in 3.90.

Edited by Pharisee
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If you own a 60CSx or one of the variants and are running software version 3.90 then you sould be aware that there is now a new version 4.00 available that, amongst other things

QUOTE from Garmin:-

 

Fixed WAAS information not showing 'D' in satellite bars. Error was introduced in 3.90.

 

Where did you get this info? I'm wondering if there is a similar issue with the oregon (although I have the most current update)

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If you own a 60CSx or one of the variants and are running software version 3.90 then you sould be aware that there is now a new version 4.00 available that, amongst other things

QUOTE from Garmin:-

 

Fixed WAAS information not showing 'D' in satellite bars. Error was introduced in 3.90.

 

Where did you get this info? I'm wondering if there is a similar issue with the oregon (although I have the most current update)

From the Garmin download website.

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Oh dear! The Garmin marketing wonks really do have a lot to answer for.

 

Your GPSr does not indicate the accuracy of a fix because it does not know the accuracy of the fix.

 

In the science of position fixing the word "accuracy" has a very specific meaning. It means the degree of closeness to the true value. If your GPSr knew the true value, then surely it would display that value and the "accuracy" would always be zero.

 

If you want to display and observe the accuracy of your GPSr then you can do it. Input the true co-ords of a known point such as a trig pillar as a waypoint, select the distance to go page and plonk the device exactly on top of the surveyed mark. If possible, try to observe the so-called "accuracy" paramateter simultaneously with the DTG figure which really is a measure of accuracy. Notice that the two numbers are actually quite disconnected and don't even wander in sync with eachother.

Edited by The Forester
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I think I read somewhere that Garmin's position is that "if the unit says 10 feet, there's a 95% chance that you are within 30 feet" (3 times the distance). Maybe they meant 2 times the distance, which would correspond to 2 standard deviations, but then maybe the errors are not normally distributed. (Indeed, given that 6-sigma seems to happen quite a lot, I'd say that the normal distribution almost certainly doesn't apply.)

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I think that if you were to mention Six Sigma to Garmin people they'd have a pink fit. Anything that smacks of proper QA/QC seems to be anathema to them. They seem to have adopted Clive Sinclair and Alan Sugar's philosophy that the buying public are the cheapest QCers you can ever hire, so give 'em a replacement if they ask for one and do so on a no-quibble basis.

 

In terms of the FigureOfMerit(FoM) which is so crassly mislabelled as "accuracy" it's actually a crude representation of the average residuals of the least-squares best fit of the pseudo-ranges measured by the receiver. A fix might be very accurate, but if it has high residuals, even mutually cancelling ones, the FoM will show a large estimated error. The reverse can also be true.

 

Magellan is more intellectually honest by naming their FoM as "Estimated Position Error". Unfortunately they are so honest about the squirrelly nature of the FoM that they suppress it altogether when you get down to using WAAS.

 

Once you get down to an actual accuracy of a couple of metres the FoM is just noise. A vastly better estimate of actual accuracy then becomes the number of fixes you've averaged into a static fix and the length of time over which you have been averaging.

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I have to say that I have recently noticed a greatly improved accuracy on my Vista HCx. I was wondering only today of someone had switched on some extra satelites in the Kernow area or something. Haven't noticed a D in the signal bars but TBH, I don't pay too much attetion to those anyway. For the last few caches though I've been trusting the GPS more than my failing eyesight though and getting within a sniff most times.

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I have to say that I have recently noticed a greatly improved accuracy on my Vista HCx. I was wondering only today of someone had switched on some extra satelites in the Kernow area or something. Haven't noticed a D in the signal bars but TBH, I don't pay too much attetion to those anyway. For the last few caches though I've been trusting the GPS more than my failing eyesight though and getting within a sniff most times.

 

No, same satellites! But if you look at the satellite screen you'll find on some days you may have no satellites 'overhead' and if your horizon is a bit obscured by trees/buildings the ones you can pick up will give you reduced accuracy. Other days, several satellites overhead and a strong signal. On bad days I sometimes find I struggle to get better than 30feet indicated.

 

Chris (MrB)

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