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Waas

Deva Duo

By Deva Duo
in United Kingdom and Ireland

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Haggis Hunter

+Haggis Hunter

Posted
Posted

Apparently WAAS isn't available in the UK or Europe but EGNOS is, your WAAS enabled GPS will pick this up automatically, if you have WAAS switched on.

 

This however will be picked up by a certain cacher that appears to know all about WAAS & EGNOS, I wouldn't like to give you his name, as you may send him an email asking about it. He may then get a bit shirty about being Spammed :lol::lol:

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Team Ullium

+Team Ullium

Posted
Posted
My GPS is WAAS enabled, but the last I heard - some time ago, admittedly - this system wasn't available in the UK and Europe.

Does anyone know any different?

Hi Deva Duo :lol:

 

just ignore that couple of scallywags :D:lol::lol:

(btw it is not me that they are referring to ... I hope? LOL)

 

If you go to the bottom of the forum you will see a search facility...if you select 'United Kingdom' and '90 days' and enter 'WAAS' in the enquiry box you will get loads of previous threads on the subject!

 

Cheers,

Ullium.

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Deva Duo

Deva Duo

Posted
  • Author
Posted

:) Thanks for your help.

 

The following is from the European Space Agency website:

The highly accurate navigation information coming from European Geostationary Navigation Overlay Service (EGNOS) is available to those with a GPS-EGNOS (or WAAS) enabled receiver. Consisting of three geostationary satellites and a network of ground stations, EGNOS will achieve its aim by transmitting a signal containing information on the reliability and accuracy of the positioning signals sent out by the Global Positioning System (GPS) and the Global Orbiting Navigation Satellite System (GLONASS). It will allow users in Europe and beyond to determine their position to less than 2m compared with about 15m at present and also be informed about the quality of the signal received.

EGNOS is a joint project of the European Space Agency (ESA), the European Commission (EC) and Eurocontrol, the European Organisation for the Safety of Air Navigation. It is Europe’s contribution to the first stage of the global navigation satellite system (GNSS) and is a precursor to Galileo, the full global satellite navigation system under development in Europe.

EGNOS will start operations in 2005 for the general public while it is planned to have the signal certified for safety-of-life use in 2006. In the meantime, a test signal, broadcast by two Inmarsat satellites, allows potential users to acquaint themselves with the facility and test its usefulness. Some of the current applications of EGNOS include minimising traffic congestion, maritime navigation and indoor positioning for firefighters.

 

 

Deva Duo

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wildlifewriter

+wildlifewriter

Posted
Posted
How would I know if I'm recieving WAAS signals?

I heard that on my satellite display it was when satellites with numbers above 33 were showing as having a signal. This does happen occasionally.

Is this different for EGNOS?

 

There are two issues, here...

 

1) Receiving the EGNOS signal.

2) Making use of it.

 

On "mainstream" handhelds (Garmin/Magellan) the signal strength bars may indicate that a signal is present, but not necessarily that the signal is being used to apply differential corrections. Some units will display an upper-case "D" in or over the signal bars, when the latter is happening.

 

The latest schedule for EGNOS to go live appears to be "Q1-2005" - that's now two years behind the original target... :)

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Stuey

+Stuey

Posted
Posted
<_<

Try going to cornwall on the north coast,logged it there recently.

Had 10 D's on the gpsr!! :lol:

Will try it out next time I'm down in the The Gower, thats about as close to North Cornwall as I can get these days :blink:

It was very selective though, geographically speaking. Davy Boy was about 40 miles away from me when he called me on the phone to see if I could get WAAS as well. I was quite high up on a Tor, but still couldn't receive the WAAS signal.

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Fangsy

+Fangsy

Posted
Posted
It was very selective though, geographically speaking. Davy Boy was about 40 miles away from me when he called me on the phone to see if I could get WAAS as well. I was quite high up on a Tor, but still couldn't receive the WAAS signal.

Strange, I wonder if it is possible that the signal was being transmitted in a much more confined direction for testing purposes, might be quite a narrow beam.... <_< now where did I put that tin foil hat... :lol:

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davy boy

+davy boy

Posted
Posted
It was very selective though, geographically speaking. Davy Boy was about 40 miles away from me when he called me on the phone to see if I could get WAAS as well. I was quite high up on a Tor, but still couldn't receive the WAAS signal.

Strange, I wonder if it is possible that the signal was being transmitted in a much more confined direction for testing purposes, might be quite a narrow beam.... :unsure: now where did I put that tin foil hat... :unsure:

I was with 2 other cachers at the time of logging waas and they had the same gpsr's and they could not log it either!!!!

(Woodbury walker and Wadders)They were very frustrated to say the least.

Garmin etrex vista,how can one log waas and the other two not? The only thing i can think of is they were running later software.

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Pharisee

+Pharisee

Posted
Posted
It was very selective though, geographically speaking. Davy Boy was about 40 miles away from me when he called me on the phone to see if I could get WAAS as well. I was quite high up on a Tor, but still couldn't receive the WAAS signal.

Strange, I wonder if it is possible that the signal was being transmitted in a much more confined direction for testing purposes, might be quite a narrow beam.... :unsure: now where did I put that tin foil hat... :unsure:

I was with 2 other cachers at the time of logging waas and they had the same gpsr's and they could not log it either!!!!

(Woodbury walker and Wadders)They were very frustrated to say the least.

Garmin etrex vista,how can one log waas and the other two not? The only thing i can think of is they were running later software.

A very obvious question but I suppose you did actually have WAAS 'enabled' at the time?

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Stuey

+Stuey

Posted
Posted
It was very selective though, geographically speaking. Davy Boy was about 40 miles away from me when he called me on the phone to see if I could get WAAS as well. I was quite high up on a Tor, but still couldn't receive the WAAS signal.

I was with 2 other cachers at the time of logging waas and they had the same gpsr's and they could not log it either!!!!

(Woodbury walker and Wadders)They were very frustrated to say the least.

Garmin etrex vista,how can one log waas and the other two not? The only thing i can think of is they were running later software.

A very obvious question but I suppose you did actually have WAAS 'enabled' at the time?

Obviously :unsure:

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The Hokesters

+The Hokesters

Posted
Posted

I don't suppose there is a definitive answer here but here goes...

 

Is there any point in enabling WAAS if WAAS and EGNOS (or EGGNOGG or whatever its called) is not yet available?

 

Or is it available? I can't make head nor tale of all the various topics on this issue.

 

All I do know is that my Garmin Geko 301 manual says that WAAS uses more battery power so I turned it off. The most accuracy I get is 15feet and that is when there was a full screen of visible satellites.

 

Si

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wildlifewriter

+wildlifewriter

Posted
Posted
Thought 30 minutes plus would be long enough.

 

Not nessescelery. My understanding of these things is like that of a hamster contemplating a new and very complicated wheel, but here goes...

 

When WAAS-mode is first enabled on your GPSr, it has to download a set of parameters from the EGNOS system, before being able to apply corrections. BUT... this data is only transmitted at intervals. If your receiver misses a segment, it has to wait for it to "come round again".

 

(This is a gross over-simplification of what is really happening, but it's good enough for us hamsters.)

 

It's very easy for a data string to be missed, first time round, because the IOR satellite is low on the horizon (from the UK) and its signal isn't very strong.

 

The only time I tried the experiment for myself, it took between three and four cigarettes for my GPSr to make sense of the EGNOS signal. :P

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wildlifewriter

+wildlifewriter

Posted
Posted
So which came first? EGNOS or Bronchitis? :P

 

Neither. This (according to Michael Green) is related to the method used to measure distance by Arabian camel drivers...

 

"How far to Inshalah, O Son of the Desert?"

"Twelve cigarettes, Effendi..."

 

An advantage of this system is that it adjusts automatically to the event being timed. For instance: it takes me 4 cigs to write 500 words on any given topic; 2 cigs to read a forum post by "The Forester", 8 cigs for the taxi to arrive when they say it'll be here in ten minutes; 6 cigs to watch an episode of "Inspector Morse", and 0.004 cigs to change channels when a programme comes on featuring Mr. Jeremy Clarkson.

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The Forester

+The Forester

Posted
Posted (edited)
What only 2?

Perhaps WLW is one of the literati of the hamster world who knows his possessives from his plurals and can read without moving his lips and doesn't need to track every word of text with his forefinger when reading.

 

That, and perhaps a generous habit of letting his ashtray smoke one cig while he smokes another, might explain the apparently fast reading time of 2 cigs to ingest a non-carcenogenic post?

 

Sounds reasonable to me.

 

I'm typing this v-e-r-y slowly for the slow reader.

 

Now, about WAAS ....

Edited by The Forester
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The Forester

+The Forester

Posted
Posted
Is there any point in enabling WAAS if WAAS and EGNOS (or EGGNOGG or whatever its called) is not yet available?

 

Or is it available? 

Seriously could anyone answer my question or am I wasting my breath [cough]!

 

Pardon me for dragging the thread back onto topic.

 

Yes, the EGNOS flavour of wide area augmentation is available, from most places around Europe and North Africa and Asia Minor and for most of the time.

 

EGNOS is available ("live") right now and is useable for all except safety-critical tasks such as precision approaches by aircraft. In geocaching, GPS is not a safety critical factor.

 

WAAS is not available to you unless you enable WAAS on your GPSr! Just switch it on and use it wisely.

 

To see the improvement in acccuracy for yourself, go to a conveniently accessible trigpoint (or any other trigpoint!) and note the co-ordinates which your GPSr indicates with WAAS enabled and then with WAAS disabled.

 

To find a suitable trigpoint, I recommend www.trigpointinguk.com/trigs/

 

To obtain the official co-ords of a trigpoint, I recommend www.gps.gov.uk

 

Be sure to use the ETRS89 co-ordinates, which are functionally identical to WGS84 for our purposes, for this test and be sure that your GPSr is set to WGS84 datum.

 

For this test, which will probably show you an accuracy of something like 3 metres (better if you can average lots of fixes) don't use the GPSr's internal conversion to/from OSGB36. That conversion is a lot less accurate than a good WAAS-assisted fix.

 

Cheers, The Forester

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Team Ullium

+Team Ullium

Posted
Posted

I understood that EGNOS was only opperational in test mode at present and wouldn't be fully up and running until sometime next year?? And even then, because it would be so low in our sky (the UK being so far north) our reception at best might be hit and miss!! Now correct me if I'm wrong but unlike the normal satellites the EGNOS satellite is a geo-stationary one!?

 

Also, because it is at present only transmitting in test mode it is not transmitting continually?...and in any case that the resulting positional corrections might not even be as accurate as the present readouts we are at present receiving purely because it was using test mode and they might be making special adjustments??

 

Now at the beginning of this year this was the state of affairs that the Rambler's forums were discussing...of course things might have changed since then....but certainly around April I and a French walker did some tests along the lines that Forester suggested and we found it was not worth a curdy (sorry it was less accurate LOL).

 

Now am I being told that if I can get the EGNOS corrections on my GPSr then it will be worthwhile leaving my Garmin set to receive it all the time???

 

(Remembering of course that my specially tuned Garmin 76 now kicks down to inches and not feet like the rest of you poor cachers have to live with LOL LOL LOL.)

 

Ullium.

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wildlifewriter

+wildlifewriter

Posted
Posted
I understood that EGNOS was only opperational in test mode at present and wouldn't be fully up and running until sometime next year??

That is correct...

 

And even then, because it would be so low in our sky (the UK being so far north) our reception at best might be hit and miss!!

... and so is that.

 

Now correct me if I'm wrong but unlike the normal satellites the EGNOS satellite is a geo-stationary one!?

Well, there are several EGNOS vehicles - they're all (more or less) geostationary.

 

Also, because it is at present only transmitting in test mode it is not transmitting continually?

Right again.

 

and they might be making special adjustments??

They might do anything during the test phase - including transmission of correction data which is hours out-of-date.

 

It's a matter of choice, whether or not you choose to use a system which is still being tested and adjusted.

 

I, personally, choose not to. :blink:

 

Wlw. (Post time: 1.8 cigarettes.)

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davy boy

+davy boy

Posted
Posted

Can anyone work this one out,was at Lynton today up on the coast path and turned on the waas and there it was lots of d's and sats.

But i hope someone can answer this question,why is it when waas was enabled i had acc on gpsr of 35ft and when disabled i had acc of 15ft???????

What happened to the 3ft acc it is supposed to give?????

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Team Ullium

+Team Ullium

Posted
Posted (edited)
QUOTE 

and they might be making special adjustments??

 

They might do anything during the test phase - including transmission of correction data which is hours out-of-date.

 

The reason for that could easily be explained by what Wildlifewriter said about the signals being just 'test' signals at the moment!

 

Ullium.

I thought I better add the quote in case you missed the point :D

Edited by Ullium
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The Forester

+The Forester

Posted
Posted
correct me if I'm wrong but unlike the normal satellites the EGNOS satellite is a geo-stationary one!?

 

There are two satellites which transmit EGNOS's WAAS data. They are both InMarSat sats, which are mostly used by homesick mariners to chat to their wives (or eachothers wives or other wimmin :D ) or to call the office on the beach. Neither sat is part of the NavStar constellation.

 

One is positioned in the Clarke belt above the equator over the Indian Ocean. That one is extremely low above the horizon from Govan (55° 50.35'N 04° 20.22'W).

 

The other one is hovering above the North Atlantic. That's the one which we in Scotland can 'see' and use usefully. It's well above the local horizon for us in Scotland and can be received from most places which have a good view of the SouthWest.

 

The testers are mostly based in Italy, from where the Indian Ocean Region InMarSat is easily 'seen'. They use that one for most of their calibrations of the EGNOS system, but they are not testing the IOR sat as such.

 

For a Govanite (no! not a hardrock mineral!!) the best waas sat to look for is the Atlantic Ocean East one. That's the one which gives us our lovely cheap differential data.

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Alibags

+Alibags

Posted
Posted
why is it when waas was enabled i had acc on gpsr of 35ft and when disabled i had acc of 15ft?

GPS view of the staellites occluded by face pressed in close to admire all the Ds on the screen perhaps?

 

I have mine enabled, my sometime geocaching partner, with the exact same GPS has his enabled too. He NEVER gets any little Ds and so gets frustrated. I don't think it makes a blind bit of difference to our GPS's which always seem to point in the same direction/distance.

 

We are further South than Govan, by the way.

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Team Ullium

+Team Ullium

Posted
Posted
We are further South than Govan, by the way.

 

Hahahaha....I dearly wish I was further south than Govan as well Alibags LOL

 

Yes I must admit that I fail to see any improvement in accuracy when I have WAAS switched on and manage to receive the signal...in fact quite the contrary...for some odd reason I have always noticed a worsening of accuracy rather than an improvement....I daresay it could be that with the WAAS switched on I am receiving a more accurate readout of accuracy....but I don't think so :lol:

 

At the moment I am more than satisfied with the accuracy of my Garmin 76 which never fails to surprise me with its non-corrected accuracy!!

 

Ullium.

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The Hokesters

+The Hokesters

Posted
Posted (edited)

Had 'distance to co-ords' down to less than 1 ft (on and off) yesterday with WAAS on. As we were watching the arrow we didn't have the page where it tells you what the accuracy is but I am glad to say we were only 2ft from the actual location. Taking into account the cache placer's GPSr accuracy I thought this was pretty bl**dy good.

 

Still took us 15 minutes or so to find though!

 

Moronic Atomic 2 - Oxford

Edited by The Hokesters
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Team Ullium

+Team Ullium

Posted
Posted (edited)

As one cacher pointed out....unless the placer of a cache had been using WAAS when they recorded the co-ords for the sheet....then it becomes irrelevant :lol:

 

We all need to be singing the same song in this respect....and for the moment anyway...I would think that one stands a better chance of being reasonably close to the placers co-ords with WAAS switched off than we are likey to be with it switched on!?

 

Ullium.

Edited by Ullium
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The Forester

+The Forester

Posted
Posted
why is it when waas was enabled i had acc on gpsr of 35ft and when disabled i had acc of 15ft?

How did you measure the accuracy?

:lol:

Eerrhh!! Tells you on the display!!

A much perpetuated fallacy seems to be self-generating there.

 

Your GPSr cannot tell you how accurate it is.

 

If it knew what the accurate position was, it would tell you so. It does not know what the accurate position is. It can only tell you where it thinks it is.

 

The fallacy that the quality indicator shown on GPSrs is an indication of accuracy is based on ignorance:- both of what accuracy means and an ignorance of how GPS works.

 

Accuracy is an expression of closeness to the true value. Your GPSr does not know the true value, so it cannot tell you how close it is to the true value. Therefore, it cannot tell you how accurate it is.

 

The quality indication figure which your GPSr shows you is a quite different thing.

 

If you ask Garmin how they derive their quality indication figure, I think you'll probably get the same answer I did when I asked them. They said that it's proprietary information which they choose not to disclose. I used to have a Garmin95, which is functionally identical to the G12 other than the top-level software. It has the lovely advantage that there are some undicumented features which allow you to download the pseudorange data if you know how to do it.

 

I disassembled some fixes from that machine and picked apart the quality indication figure. I reckoned that a very good approximation was the 2Sigma value of the standard deviation of the residuals of the fix.

 

Now, let's leave aside the techy jargon and lemme explain this stuff in simple terms.

 

Imagine an idealised fix, in which you have four satellites, each low on the horizon at the four cardinal points of the compass.

 

Let's say that on the first day of your observation the ionospheric and tropospheric conditions are such that each satelllite's pseudo-range over-indicates by 10 metres. That overage is called a 'residual' in the jargon. That overage will be indicated in the quality indication of the fix.

 

Now, let's take another day, when the same four sats give an overindication of just 5 metres each.

 

The Northern satellite is counterbalanced by the Southern one. The Western by the Eastern one.

 

Are the two daily fixes better or worse than eachother?

 

Does the quality indicator give an indication of which is the more accurate fix?

 

NO!!!

 

The only way you can judge the actual accuracy of your GPSr is by plonking it on a known location, such as a trigpoint, and noting the indicated co-ordinates.

 

Cheers, The Forester

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Team Ullium

+Team Ullium

Posted
Posted (edited)

What Forester says makes a lot of sense....and I must admit I always assumed that the accuracy figure shown on any GPSr was mathematically calculated on assumed error factors accrued from the information output by each individual satellite being received....and it was calculated on much the same principles as one would calculate the assumed error accrued within a mathematical computer program given the value of the inputs!

 

I really think the title of this particular readout should be 'Expected Accuracy' or even 'Optimistic Accuracy' :lol::lol::lol:

 

But that is just my thoughts on the subject :huh:

 

Ullium (whose brain cells are dying off faster than the Autumn leaves :mad: )

(and can't spell for toffee....then what do you expect from a Govanite :huh: )

Edited by Ullium
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The Forester

+The Forester

Posted
Posted
I always assumed that the accuracy figure shown on any GPSr was mathematically calculated on assumed error factors accrued from the information output by each individual satellite being received....and it was calculated on much the same principles as one would calculate the assumed error accrued within a mathematical computer program given the value of the inputs!

I don't know exactly how either Garmin or Magellan do their quality indication figure, but I've got a good idea.

 

I'm sure that it's a scalar quantity of the error ellipse.

 

I think that Garmin does something freaky with the residuals to make up their weight matrix in their formulation of the least squares solution. I just don't know what. I'm just not clever enough for that stuff.

 

Cheers, The Forester

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LordLucan

LordLucan

Posted
Posted

Thank you Forester and Ullium, I have just started caching in Perthshire and have only found one cache so far. The descriptions of accuracy will indeed now help me as i believed what the Garmin was telling was correct I will allow for an error radius. The caches I have been looking for by Perth Pathfinders AllieBallie and Snaik appears to be Dastardly and Devilish. Myself, Beverly and the canines Sherlock and Moriarty have thoroughly enjoyed the forays so far, thank you again. LL

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Team Ullium

+Team Ullium

Posted
Posted
(and can't spell for toffee....then what do you expect from a Govanite  :lol: )

A wee non-waas cache maybe, hidden somewhere between Govan and Perth

 

:lol::lol::mad:

I get the same feeling when I used to take the kids to the zoo and they were all in the back of the car saying.....

 

"Are we there yet?...are we there yet?...are we there yet?....are we there yet? ...."

 

:):):huh::huh::o:):D:)

 

Mark you ...on reading one of your logs Snaik...I see you like to bypass all the working out of puzzle caches and go straight to the container and log the find....and a couple of days later do all the calculations for the co-ordinates? B)

 

So I can see my first cache had better be something really special to challenge a man of your skills ;) I am consulting a witchdoctor and a medium for some advice :P

 

Ullium.

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Team Ullium

+Team Ullium

Posted
Posted
Thank you Forester and Ullium, I have just started caching in Perthshire and have only found one cache so far. The descriptions of accuracy will indeed now help me as i believed what the Garmin was telling was correct I will allow for an error radius. The caches I have been looking for by Perth Pathfinders AllieBallie and Snaik appears to be Dastardly and Devilish. Myself, Beverly and the canines Sherlock and Moriarty have thoroughly enjoyed the forays so far, thank you again. LL

Ah LordLucan I can see your problem and I can sympathise as you are up against three dastardly clever opponents there :lol::lol::lol:

 

Welcome to the madhouse LL :huh:

 

I have no doubt your numbers will quickly increase....especially with the help of Sherlock and Moriarty :mad:

 

Ullium.

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Haggis Hunter

+Haggis Hunter

Posted
Posted

Well I am glad some people can understand all of this jargon, I must be thick as I haven't got a bloody clue what you are trying to explain.

 

When The Forester said -

Now, let's leave aside the techy jargon and lemme explain this stuff in simple terms.

 

I thought great i'll be able to understand now, but I didn't notice any difference in the explanation.

Think i'll just rely on my ignorant ways and trust the findings of my GPS, I mean 217 caches can't be that far ignorant??

 

Thanks for trying to explain it anyway.

 

Oh yeah Snaik, Great Avatar :lol::lol::lol:

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