Waas On Or Off

[+spioradsaor]

Hi Peeps,

 

I know this has probably been covered before...But fed up with flyfisherman Bob following my wheelbarrow racks (I use it to move the old magellan around) I have a new smart machine which does not require he wheelbarrow. However should the WAAS signal be on or off.

 

Didnt have this problem with the steam driven magellan I'll tell you.

[+The Forester]

The InMarSat Atlantic Ocean East satellite is not currently transmitting the EGNOS (European equivalent of the American WAAS) data.

 

EGNOS is being transmitted from the Indian Ocean satellite, but that's too low on our horizon for us in Scotland to receive.

 

The plan is for the Artemis satellite to transmit the data, but there was an upper stage launch whoopsie and it's taken many many months for the engineers to nurse her into a useful orbit.

 

The EGNOS data that we used to receive here in Scotland was only in test mode and carried a health warning that it would be discontinued at very little notice and should not be used for safety critial purposes.

 

Don't worry, your new luggable GPS will soon be giving you razor sharp fixes.

 

Watch this space ....

 

Cheers, The Forester

BTW, if you email me an ordinary email address, I'll send you a diagramme which shows exactly why we can't get WAAS/EGNOS at the moment.

Edited August 12, 2004 by The Forester

[+The Forester]

Whoops! Sent the message twice. Sorreee

Edited August 12, 2004 by The Forester

[+sTeamTraen]

There's a hype story on BBC Teletext today about how security people at the Olympics are using EGNOS to zoom in on muggers, accident victims, terrorists, etc. I presume it was written a year ago when everyone thought EGNOS would be up and running by April 2004.

[+The Forester]

EGNOS is up and running, for most practical purposes. It just hasn't completed the certification process for safety critical applications such as airliner instrument landings yet.

 

It is still under the aegis of the ESTB programme and won't be certified until Q4, but it certainly is up and running.

 

The issue for us up here in the top left hand corner of Europe is that we haven't got good line of sight to the only EGNOS satellite which is perched over the Equator and the Indian Ocean. That's a separate issue from EGNOS itself. The testers simply don't need the Atlntic satellite for their tests, so we here in Scotland can't access the service at the moment.

 

For use by the emergency and security services in Athens, EGNOS is fully functioning.

 

It's still in mode 2 (all corrections except orbit ones), but that still gives better than 3 metre accuracy and is a great boon.

 

Cheers, The Forester

[+Haggis Hunter]

I have mine switched on, it makes no difference at the moment, but when it does go live you know you are going to get the facility immediately.

[+Flyfishermanbob]

How am I supposed to find anything now ????????!!!!

 

Re WAAS as has been said Sept 1st is supposed to be the go live date ….current data is being sent with an “ignore bit” set so whether its set on or off on the GPSr wont matter as most GPSr manufacturers check this “ignore bit” and disregard the signal.

 

Except Magellan who read it … hence you could get led a merry dance ( as I did till I switched it off)

So bottom line is unless it’s a Magellan switch it on ..if it’s a Magellan I’ll let you know how to “ disable it” ( it’s a boot up jobbie )

 

Anyway its all hype … 12 feet or 3 feet … wow I’m impressed … and it wont help you unless the cache placer had WAAS and it worked ( remember one of the last caches you did … Waas wouldn’t help… it was a football pitch out )

 

I’m sure there must be a conspiracy old Poots is putting caches in cities and Spiro has got rid of the wheelbarrow …….

[+wildlifewriter]

current data is being sent with an “ignore bit” set so whether its set on or off on the GPSr wont matter as most GPSr manufacturers check this “ignore bit” and disregard the signal

 

There's more to it than that:

 

To understand what's happening at the moment, let's anthropomorphise for a moment and imagine what a GPSr does, when it sees one of the SBAS-type satellites...

 

(These comments generally refer to a Garmin consumer unit, and an eTrex type in particular.)

 

1)I can download the almanac (orbital information) for this satellite. So far, so good.

 

2)I now know which satellite it is, and what it's supposed to be doing. THIS one is supposed to be transmitting SBAS information, for me to use in positional corrections.

 

3)None of the information appears to be any use. I am not going to waste one of my receiver channels listening to this garbage. Ignore it. OR...

 

(4)The information appears useful, but it doesn't apply to the area where I am, now. It might be useful some other time, but ignore it for now. OR...

 

(5)The information is valid, and applies to HERE. However, the satellite is also transmitting the “DO NOT USE” indicator. Maybe it's faulty, or under maintenance. Because I'm a Garmin GPSr, I know not to apply the corrections, 'cos they might be wrong. However, I'll remember THIS satellite for future reference.

 

(6)OK. Now.. lets listen to see if there are any other SBAS satellites which I can use.... (back to (1))

 

Paul

[+sTeamTraen]

Anyway its all hype … 12 feet or 3 feet … wow I’m impressed … and it wont help you unless the cache placer had WAAS and it worked ( remember one of the last caches you did … Waas wouldn’t help… it was a football pitch out )

In general, it would be nice if people would give us an idea of how their GPSr was performing when they placed a cache. I'm already very wary of coordinates when looking in summer for caches placed in deciduous woods in winter !

 

However, I don't agree that better accuracy doesn't help. It's all a question of statistics. The posted coordinates are more likely to be "accurate" if they were done with WAAS, but they might also have been done by taking five readings, walking 20 metres away and coming back each time, and taking the average. This is what I do with every cache I place. In practice (especially if the finder does the same), that gets you a pretty fair chance of being "close".

 

Of course, it also helps if the cache placer types the bloody numbers right; compare the waypoint with the cache description here, it caused some experienced cachers to go a a few km out of their way !

[+wildlifewriter]

In general, it would be nice if people would give us an idea of how their GPSr was performing when they placed a cache.

 

Just a thought (and somewhat OT) but if everyone had decimetre-accurate equipment for placing and finding caches - the whole thing: WADGPS, phase differentials, etc, - would it not ruin the hobby completely...?

[+Team Ullium]

Early this year there was a big debate on whether it was useful to leave WAAS switched on or not and the general feeling was that it was better .. at the moment .. to be left off...for all kinds of technical reasons.

However, in the process of the debate I got this link to the EGNOS news letter and found it very useful :-

see here

or here for the website

 

Ullium

Edited August 13, 2004 by Ullium

[+The Forester]

if everyone had decimetre-accurate equipment for placing and finding caches - the whole thing: WADGPS, phase differentials, etc, - would it not ruin the hobby completely...?

I see your point, but I don't think it would ruin geocaching. In fact it is feasible that it might even tighten and sweeten geocaching still more.

 

For one thing, much of the pleasure of a good cachehunt is enjoying the environment and a good walk. I've been on plenty of cachehunts where the boxfinding was just the cherry on the icing of the cake. Some of the rural sites in such places as Perhshire and the Highlands of Scotlnd are good examples of a great walk. Take a look at some of the lovely ones created by Snaik and Perth Pathfinders to see what I mean.

 

Another point is that many caches are very educational and entertaining, especially some of the walking tour multipoint ones such as Edinburgh's Up the Close and Down the Stairs or Leith's Ships Claret & Golf. In such cases, highly accurate position fixing is almost completely irrelevant

 

Even with razor sharp position-fixing, we would still be guided by geocaching to lovely places which would otherise probably never get round to visiting or might never even become aware of.

 

Then there is the fact that some caches are hidden in locations where there is heavy masking of the GPS signal by terrain or buildings or dense foliage. Remember too that with WAAS you've also got to have a clear line of sight to the relay satellite.

 

Undoubtedly clever cachesetters would factor this into their choice of location to make the hunt more challenging. In fact I already know of one cache which is underground where there is no signal at all.

 

Cachesetters would also spend more time and effort and ingenuity in choosing very difficult to find hidey holes and selecting or even making more inconspicuous containers than the ubiquitous ammo cans and tupperware boxes. I've visited about a dozen caches where I'd been within a metre of the thing several times and for several minutes without spotting it. As the resolution of the third decimal point of a Minute is a couple of metres, the co-ords can only ever get you to within looking or perhaps feeling distance.

 

I think the only caches whose quality would suffer for the seeker with WAAS and good quality co-ords would be the boring carpark/layby ones which are already no particular challenge anyway.

 

Cheers, The Forester

[+sTeamTraen]

Cachesetters would also spend more time and effort and ingenuity in choosing very difficult to find hidey holes

I hope that they would only do that for places which have a year-round clear view of the sky. This cache probably never has accuracy better than 20 metres - it's under thick evergreen tree cover.

 

WAAS, EGNOS, or not, you're still going to have problems if you can only get a signal from three satellites. And if there's a large mountain directly to the south, that'll probably be EGNOS offline, even when ESA do get round to hosting it on a satellite more than 3º above the horizon.

Edited August 13, 2004 by sTeamTraen

[+The Forester]

This cache probably never has accuracy better than 20 metres - it's under thick evergreen tree cover.

 

"I found it in about 30 seconds ! GPS reception was so bad (over 30 metres "accuracy", whatever Garmin's marketing department means by that) that I switched it off and went exploring. The hint was all I needed."

 

There's an important lesson in there!

 

On several occasions I've found the co-ords to be flat wrong. I was only able to really start the terminal phase of the hunt once I switched off the GPS and started reading the ground and looking for sign and using some of the tricks which the experienced cachers use, such as asking myself 'where would I hide it?'

 

It's another reason why I don't think that the sport will be adversely affected by the introduction of WAAS/EGNOS.

 

Actually, I think it will educate some people into learning some of the real arts of navigation. Needle chasing, head down and tail up, carries several hazards quite apart from the obvious one of clonking your head on lamp-posts and tree-trunks. Too much reliance on the GPS distracts you from reading the vegetation and other signs of a nearby cache. I think some people will learn that greater accuracy of the GPS does not necessarily make it a more useful tool. Sometimes it is better to go back to first principles and use a map and a compass and a sharp pair of eyes and a bit of grey matter.

 

That having been said, I'd still rather have WAAS/EGNOS than not!

 

 

Cheers, The Forester

[+Team Ullium]

That having been said, I'd still rather have WAAS/EGNOS than not!

 

Who wouldn't ?...as long as it is not counter productive!?

 

Which it could very well be at the moment according to the hill walkers on the Ramblers forum.

 

Until the EGNOS bird is fully functional I would suggest that it is more prudent to leave WAAS switched off

 

And that advise is from people who are putting their lives on the line ... not just whether they are bagging a geocache or not

 

Ullium.

[Trudge]

What is the problem with using WAAS if the signal is good?

Edited August 13, 2004 by Trudge

[+Team Ullium]

At the moment apparently only test signals are being sent....now these could be good...as you put it...but on the other hand the error factor might easily be greater than normal...purely because it is a test signal

 

Leaving in switched on all the time just means you are adding an extra load on your GPSr processor and for what?....maybe you will get a more accurate readout...and then again maybe you won't

 

At the moment the error factor incurred by not selecting WAAS is not all that bad...certainly good enough for geocaching....and remember that all the caches are set by the co-ords given by GPS units receiving non EGOS signals.

 

Personally until it is up and running fully functional I would suggest it is not worth the trouble....and even if it were....as The Forester points out it will be very low on the horizon for us chappies so far north so it's reception will always be rather iffy

 

Ullium.

[+The Forester]

Until the EGNOS bird is fully functional I would suggest that it is more prudent to leave WAAS switched off

 

Yes. If the signal is not being transmitted, why try to receive it?

 

I'm puzzled why the ramblers are unhappy about WAAS. Any ideas what problem they have with a system integrity assurance monitor? That's part of what WAAS actually is. The Differential corrections which improve the accuracy are a bonus, not a hazard.

 

Did these people also have reservations about SA being switched off? If so, why?

 

Did they have resevations about the old Transit SatNav sytem being replaced by NavStar GPS?

 

Did they find any problem with EGNOS when we had it here in Scotland for all those months last year?

 

I don't understand why an improvement in a navigation system should be resisted by civilians. I understand the military reservations. I was one of many who campaigned for years to try to persuade the Pentagon and the White House not to switch on SA in 1990. They threw a lot of sand in our eyes and came up with some very fanciful and far-fetched reasons to back up their claim that SA was vital for US national security, but they never went to far as to claim that improving the accuracy of GPS would endanger hillwakers.

 

I'm curious to know what the perceived problem is with WAAS. Why don't those people want us to have it? Is it because GPS has deskilled and dumbed down mountain navigation? If so, it is the users who need to be addressed, not the WAAS system.

 

Cheers, The Forester

[+Team Ullium]

I'm puzzled why the ramblers are unhappy about WAAS

 

I see you are aware that the WAAS system was set up for the US military and was intentionally degraded for non-military use!

 

So perhaps you mean EGNOS...which is the european equivalent system being set up as we speak....I realise it piggy backed the WAAS system for a while but if you read the two links I put up you might come to the same conclusion !?

 

We all experienced periods of increased accuracy during the period you referred to ... but that accuracy became very suspect later on this year.

 

No one has any crib about increased accuracy and remember we are not talking about WAAS...which we can't recieve ...degraded signal or otherwise ....but EGNOS which is still being set up and very much in a flux situation....and even when it is up and running as you pointed out it will still be very low on our horizon.

 

The hillwalkers crib was that they ON OCCASION got reduced accuracy....and let's face it ....these guys can't take a chance that the reading they are getting is not one of those occasions

 

Ullium.

[+klaus23]

Just my own 0.02 worth - but I leave WAAS off, as I rarely get a 'D' bar on my GPS - and find that the battery life has improved since I did so...

[+The Forester]

the WAAS system was set up for the US military and was intentionally degraded for non-military use!

EGNOS is a Wide Area Augmentation System (WAAS). So is MSAS, the Japanese equivalent. All three systems are WAAS.

 

They are civilian, not military. The US WAAS was degraded during its testing while SA was still switched on because if it had not been, then it would have make a monkey out of the whole concept of SA, just like DGPS did. It wasn't degraded by the military because the military never operated it.

 

Yes, I occasionally describe EGNOS and MSAS as WAAS because all three systems are WAAS. You can use a WAAS-enabled receiver as easily in the coverage areas of all three WAAS systems. Even the manufacturers such as Magellan refer to EGNOS usage as "WAAS".

 

The US WAAS system is owned by the FAA (actually, the Dept of Transportation), not the DoD, despite the fact that the NavStar (GPS) system itself is entirely a USAF affair. The US WAAS was always a civilian project in concept and execution, never military. With dual fequency receivers using the Precise miltary code, the military didn't really need WAAS. Only the civil sector really needed it.

 

"The hillwalkers crib was that they ON OCCASION got reduced accuracy"

 

Ahh! I see. Now all is clear to me. I misunderstood when you earlier said that "as long as it is not counter productive!? Which it could very well be at the moment according to the hill walkers on the Ramblers forum."

 

I musunderstood, thinking that you meant they thought switching it on could be counterproductive.

 

We were all warned that during the testing phase it could be switched off with little or no notice and that its signal should not be used for safety sensitive purposes. I suppose it is inevitable that some people would ignore the warnings.

 

Actually, I personally believe that any hillwalker ever gets themselves into a situation where his or her safety depends on GPS really needs to reevaluate his or her competence to be navigating in the hills in the first place. GPS, with or without SA and with or without a Wide Area Augmentation System, is an aid to navigation, that's all. It can fail at any time without warning. In fact my own GPSr suddenly failed on a caching trip in Upper Deeside only a couple of months ago. It quite simply stopped working, despite trying several sets of fresh high quality batteries. That put a crimp in my cachehunt, but its loss was never a safety issue for me on the hill.

 

The only substantial risk I can see from making GPS so very handy is that it might possibly encourage some people to take risks without an adequate knowledge of how to navigate by traditional means. The answer to that problem of course is to encourage them to learn how to navigate and to learn how to assess the performance of the navaid by cross-checking its output with the real-world.

 

Actually that last bit equally refers to some very well-intentioned cache-placers who just hold their GPSr up to their face and press a button and when they see a wee cartoon figure plonk a flag in the ground on the lcd screen they think that the fix must be good and so they don't bother to check it or cross-check it, but that's another issue.

 

Cheers, and have a great time on the minicachebash, I wish I could make it there. Rannoch, Glen Coe and Glen Etive are magical places and you're going to have a wondeful day's caching.

 

The Forester

[+Team Ullium]

LOL....I stand corrected The Forester

 

It was my understanding that EGNOS used a slightly different system from the American WAAS and operated entirely independent of it!?...and the whole concept of WAAS was born out of a US militiary requirement!?

 

But you do see what I'm getting at? It is OK to take the high moral ground and say no one should rely on their GPSr readout but you and I know we all take the apparently easy way out when push comes to shove.

 

Yes of course anyone up in the hills...myself incluced should never rely on a GPSr but gee it is just so handy to know exactly where you are when calculating your route in strange surroundings and if I cant see two feet in front of me and my Garmin tells me I am at such and such....it is tempting to believe it rather than bed down for the night

 

I agree that some cache placers do not take enough care in posting their co-ords...fortunately they are in the minority Mostly the cache location is responsible for poor reception and subsequently poor initial co-ords....but hey ...it is all part of the fun eh?

 

Yes I'm off early in the morning to Glencoe....pity you couldn't make it...but these things happen and some things are more important than geocaching....I think

 

Cheers,

Ullium.

[+The Forester]

It was my understanding that EGNOS used a slightly different system from the American WAAS and operated entirely independent of it!?.

 

EGNOS is slightly different for three reasons.

 

One is that it had the advantage of being devised five years after the original WAAS, so the Euros were able to learn from some of the mistakes made by the Murricanes.

 

Another is quite simply that hitech technology in general had moved on in the five years between the inception of the two systems.

 

A third reason is that EGNOS is designed to be forward compatible with the forthcoming Galileo SatNav system which is technologically greatly superior to the 1970s technology of NavStar. An EGNOS position fix is about twice as accurate as a US WAAS one. Galileo will be even better.

 

You are quite correct that EGNOS is operated entirely separately from the US WAAS. The two systems (and the Japanese one too) are, however, completely compatible with eachother. Your GPSr will seamlessly switch from one WAAS to another without any effort by you, the operator.

 

 

"the whole concept of WAAS was born out of a US military requirement!?"

 

 

No, not so.

 

The Precise Positioning System codes are transmitted on the same frequency as the Standard Positioning System codes which we civilians use in our GPSrs. The military units produce an accuracy of about three metres, which is quite enough accuracy for them to deliver a 2,000lb bomb to a selected part of an aspirin factory in Khartoum or a restaurant in Baghdad or a religious school in Kandahar. They had no need for WAAS. Anyway, the US WAAS only covers America, not the countries which America likes to bomb.

 

WAAS was a Federal Aviation Administration (FAA) project. Its purpose is to improve the quality of aviation radio navaids while at the same time reducing the huge cost of maintaining the vast network of ground-based navaids such as VORs, DMEs, NDBs, and perhaps ILSs in the continental US.

 

"Yes of course anyone up in the hills...myself included should never rely on a GPSr but gee it is just so handy to know exactly where you are when calculating your route in strange surroundings and if I cant see two feet in front of me and my Garmin tells me I am at such and such....it is tempting to believe it rather than bed down for the night"

 

GPS is a brilliant tool for such an occasion. As happens so often here in Scotland, the mountain weather can clamp in suddenly and with little warning. Taking a swift position fix is a very good idea. I teach my proteges to write down the co-ordinates and to physically plot them onto the map, also noting the time of the fix and writing that time next to the plotted + on the map.

 

My concern is not so much for experienced navigators such as thee and me. We know how to use GPS to get ourselves out of trouble. My concern is for the inexperienced and uneducated ones who could unwisely use GPS to get themselves *into* trouble.

 

 

Cheers, The Forester

[+Team Ullium]

I'm puzzled why the ramblers are unhappy about WAAS. Any ideas what problem they have with a system integrity assurance monitor? That's part of what WAAS actually is. The Differential corrections which improve the accuracy are a bonus, not a hazard.

 

I think you may have misunderstood me there Forester!?

 

Any rambler that I know would be delighted if EGNOS was up and running and giving improved accuracy....what they were perhaps unhappy about was all the missed target dates and even when it was transmitting it could have the ignore flag set which brought into question which GPS units actually did ignore the signals and which didn't!?

 

I think most have come to the conclusion that, for the moment at least it would be prudent to leave WAAS switched off on their units until EGNOS was properly set up and running!?

 

Certainly, most recently manufactured GPS units have much improved aerials and software and the accuracy of these units are sufficient to satisfy even the most fastidious users....certainly my Garmin Marine GPS 76 is accurate enough for me when it is recieving four or more satelites.

 

Having said that of course...who wouldn't accept improved accuracy if it was there for the taking....and that is the moot point....for the moment it doesn't appear to be there for the taking

 

Cheers,

Ullium.

[+Flyfishermanbob]

A tale for all …might have some bearing:-

 

I purchased a Magellan Sportrak Colour ( Europe) over a year ago , and initially was about to send it back because of the errors ….

The Magellan has lots of functionality, everything I needed and more …but the errors were huge ( 176 feet )

 

The test I used was on the local football pitch …..at each of the corner flags and the centre spot , I allowed the unit to settle and “average” for 1 min and took a waypoint.

I then went back to each waypoint and checked how far it was “out” …worst case was 176 feet and it wasn’t consistent .

 

Did some digging and found this .. Magellan Codes.

 

THIS IS NOT a MAGELLAN DOCUMENT

 

Seems Magellan just process Waas correction info regardless of whether the disregard bit is set or not .

 

I then disabled Waas by booting up as instructed and accuracy miraculously was returned …worst case 18 feet error. And unit has been super ever since.

 

The follow-up to this , is that last week , the Magellan newsletter recommended updating the firmware ( software) to the latest release which I did , only to find there were 2 WAAS satellites showing , WAAS had been re-enabled ,so I checked against the original test and sure enough it was all over the place again.

So WAAS is now disabled !

 

I don’t know why Magellan don’t give the option to disable WAAS , but if you have a Magellan ( WAAS enabled ) try it for yourself …

 

regards FFB

[+Team Ullium]

This is precisely what most of the walkers I know experienced as well FFB ... myself included

 

At least Garmin gives you the opportunity to select whether or not you want to recieve WAAS...which is handy.

 

Also, in the process of the Rambler discussions I was involved in, it was discovered that some very experienced walkers had not selected the proper datum for the particular co-ords they had their unit set to... and that was a big factor in reducing their percieved accuracy....mark you for general walking 'pin point' accuracy is not all that necessary unless you are stuck up something like Ben Nevis in a mist... and in which case you wouldn't be wanting to trust your GPSr with your life in any event

 

Geocaching is of course different...we need the best recieving aerial and the best accuracy we can get....personally I can't wait until EGNOS is transmitting and functioning properly

 

Ullium.

[+sTeamTraen]

The military units produce an accuracy of about three metres, which is quite enough accuracy for them to deliver a 2,000lb bomb to a selected part of an aspirin factory in Khartoum or a restaurant in Baghdad or a religious school in Kandahar. They had no need for WAAS. Anyway, the US WAAS only covers America, not the countries which America likes to bomb.

LOL... and if you select the wrong target (even by those standards), it doesn't matter anyway.

 

I heard a great story, which seems utterly plausible knowing how bureaucrats work (I am one !), about how the Chinese embassy in Belgrade got it. Apparently the planners knew that the Serbian Ministry of <whatever> was at (say) number 65 in a given street, and they had the coordinates of #1 and #99. So they extrapolated between the two ("hell, how far off can we be ?"). Unfortunately the first 25 numbers took up less room than expected, so #65 was half way down, and at 2/3 was #81, the Chinese embassy.

 

As with the pilots who cut the cord on the Italian cable car a few years ago, you can bet that no manslaughter charges will be forthcoming... when will the Americans wake up to the fact that they could still be almost everybody's favourite country, if only they didn't want different rules to apply to them compared to the rest of the planet ?

[+Renegade Knight]

With WAAS enabled I see single digit EPE. I really haven't noticed much difference while seeking a cache insofar as accuracy. However it does noticably slow down my GPS V and that can be annoying.

 

Without WAAS my EPE hoovers at 15-20 feet normally.

[+EraSeek]

With WAAS enabled I see single digit EPE. I really haven't noticed much difference while seeking a cache insofar as accuracy. However it does noticably slow down my GPS V and that can be annoying.

 

Without WAAS my EPE hoovers at 15-20 feet normally.

Slowing of the processing generally comes from running heavy applications together. In other words, this is usually only a problem if you are running auto-routing and WAAS at the same time.

 

WAAS is good, but not a nessecary thing. It is just for us accuracy hounds.

[+Flyfishermanbob]

Hi EraSeek, re the quote which was made my Renegade Night about accuracy.

 

I'm sure most European cachers would be delighted to leave Waas swithed on if this were available.

 

The issue is that Waas correction currently only works in USA and Canada ....by the time you get half way accross the Atlantic ,the Waas corrections are unreliable, hence the waiting for an operational satellite to cover Europe.....

 

( but dont hold your breath...most of us will see at least one more birthday before this becomes fully operational)

regards FFB.

[+The Forester]

The issue is that  Waas correction currently only works in USA and Canada ....by the time you get half way across the Atlantic, the Waas corrections are unreliable, hence the waiting for an operational satellite to cover Europe.....

 

Most of Europe is fully covered by the European WAAS, called EGNOS. They can receive good quality data from the geostationary InMarSat satellite which is parked above the Equator over the Indian Ocean. That satellite has been producing very high quality data for almost the whole of this year.

 

That one is not 'visible' for viewers in Scotland, but I've noticed that for at least the last couple of days we have got good data from our local satellite, AOR-E -- the one which covers Western Europe including us in Scotland.

 

I measured the indicated position of a couple of points near my home in central Scotland, for which I have very high accuracy co-ordinates. My Magellan produced fixes which were within about 1.5 metres of the known position. Not bad for a wee hand-held single frequency GPSr.

 

My advice to those geocachers who have crippled their WAAS-compatible GPSr by switching off WAAS/EGNOS is to enable WAAS and enjoy the accuracy.

 

 

Cheers, The Forester

[JackiePenn]

<snip>

That satellite has been producing very high quality data for almost the whole of this year.

 

<snip>

 

My advice to those geocachers who have crippled their WAAS-compatible GPSr by switching off WAAS/EGNOS is to enable WAAS and enjoy the accuracy.

 

<snip>

My unit was using bird PRN126 in July (on and off) which was great high quality corrections.

 

Last few weeks the almanac update to use PRN124 and PRN120. PRN124 not giving as good corrections as PRN126 did but its still much better than pure GPS.

 

PRN120 is ever present but seems not to boardcasting corrections as of yet, if and when that bird kicks in I think things will be on the up.

 

When I first used my unit it seemed default to use PRN122/PRN120. PRN122 is just in range of the West of Europe but is purely a WAAS SAT (not EGNOS) so no useful corrections were being received even though a good DAT SNR was there.

 

It was suggested to me on the Magellan forums to move the GPSr to a location out of range of PRN122 (but in range of the EGNOS sats with strong signal strength) and leave it static for 15minute whilst the almanac updated. I did this and the alamanic updated to use PRN126/PRN120 and WAAS(EGNOS) was then displayed on the units screen for the first time. With EPE displayed as <3metre error.

[+Cave Troll and Eeyore]

I leave WAAS/EGNOS enabled all the time but have yet to get the Ds and less than 15 ft accuracy despite satellite 37 flashing for 45 minutes

 

Pengy & Tigger live nearby and they have add full lock more than once using the same GPSr (Garmin 60CS).

Edited September 2, 2004 by Cave Troll & Joan

[+Team Ullium]

Just a wee bit of info for those who are not as conversant with these birds :-

 

To find the GPSr Garmin ID of a GPS satellite, you must substract 87 from the prn code. Satellites having a Garmin ID above 32 are involved either in WAAS or in EGNOS

 

Satellite AOR-E (Atlantic Ocean East), prn 120, Garmin ID 33

Satellite Artemis (launched by ESA), prn 124, Garmin ID 37

Satellite IOR-W (Indian Ocean West), prn 126, Garmin ID 39

 

Satellite prn122 is therefore Garmin ID 35

 

Presently (to the best of my knowledge) only one satellite is involved in EGNOS ESTB (test bed) : Satellite IOR (prn 131, Garmin ID 44), which transmitted usable data until earlier on this year but which is very low above the horizon in UK, especially Scotland.

 

If I'm mistaken in any of the above no doubt I will be quickly corrected

 

Stonefisk:

It was suggested to me on the Magellan forums to move the GPSr to a location out of range of PRN122 (but in range of the EGNOS sats with strong signal strength) and leave it static for 15minute whilst the almanac updated. I did this and the alamanic updated to use PRN126/PRN120 and WAAS(EGNOS) was then displayed on the units screen for the first time. With EPE displayed as <3metre error.

 

I'm a bit puzzled as to how you moved your GPSr to a location out of range of PRN122 ??? Can you expand on that a wee bit

 

Ullium.

Edited September 2, 2004 by Ullium

[+Cave Troll and Eeyore]

Just a wee bit of info for those who are not as conversant with these birds :-

 

To find the GPSr Garmin ID of a GPS satellite, you must substract 87 from the prn code. Satellites having a Garmin ID above 32 are involved either in WAAS or in EGNOS

 

Satellite AOR-E (Atlantic Ocean East), prn 120, Garmin ID 33

Satellite Artemis (launched by ESA), prn 124, Garmin ID 37

Satellite IOR-W (Indian Ocean West), prn 126, Garmin ID 39

 

Satellite prn122 is therefore Garmin ID 35

 

Presently (to the best of my knowledge) only one satellite is involved in EGNOS ESTB (test bed) : Satellite IOR (prn 131, Garmin ID 44), which transmitted usable data until earlier on this year but which is very low above the horizon in UK, especially Scotland.

 

If I'm mistaken in any of the above no doubt I will be quickly corrected

 

Ullium.

Thanks for that Ullium.

I am now a little more enlightened on the subject.

I do keep checking the ESTB broadcast shedule site regularly for the latest info.

[+Team Ullium]

No probs Cave Troll & Joan

 

The latest info can be read here

 

or here

 

Ullium.

[JackiePenn]

I'm a bit puzzled as to how you moved your GPSr to a location out of range of PRN122 ??? Can you expand on that a wee bit

 

Ullium.

I'll try to expand.

 

The unit I am using is a Megallen Meridian Platinium, via a secret menu (factory settings menu) you can observe the details of the the WAAS/EGNOS sats. Things like PRN no, Transmit State (SRCH/BIT/DAT), Signal to noise Ratio (SNR), the Az and FI. Also other ungodly things like FAST/Long/long values which I have little understanding.

 

At first PRN 122 headed the line up, never changed for weeks, never seen the unit display "WAAS" to show it was using EGNOS. PRN122 state was often in "DAT" mode and the SNR was very good, but no joy. I went and asked at the Magellan forums.

 

The following was the advice given on the forum.....

 

>Hello I'm in Wiltshire UK, the ERGOS sats my meriplat pick up are:

>

>SAT 122, SNR:132, AZ:238, FI:14

>SAT 120, SNR:125, AZ:196, FI:30

>

>But no corrections are being carried out and I have yet to ever see

>the display show "WAAS" since I have had the unit.

>

>

>

As I reported earlier: I suspect that EGNOS (PRN 120) corrections are

cancelled by WAAS corrections (PRN 122).

and WAAS is not valid for your location.

 

You will only get WAAS reported if... at least 1 sat has fast and long

corrections available AND iono grid is valid.

 

Please try moving your GPSr to a location that has no reception of PRN

122, but still receiving PRN 120, and then you can get an almanac

update (takes 15 minutes of uninterupted reception: SNR bigger than 50,

smaller than 300)

IONO-grid will take 5 minutes. so display of WAAS message can be seen

after that time.

[+Team Ullium]

Thanks Stonefisk

 

I suspect this must just be a Megallen GPSr issue as I haven't experienced any problems with both the Garmin's I have used in picking up any of these birds ...whenever they are available that is !!!

 

Ullium.

[+wildlifewriter]

The following table might help, when finding the direction to 'point' your handheld GPSr, when acquiring these satellites for the first time. The Az/El is approximate for these locations: Edinburgh, Belfast, Manchester, London. (Some of the vehicles have inclined orbits - especially Artemis, so don't beat me up about the exact figures.)

 

Formatting a list is difficult in this forum interface: the columns contain (l to r) Station, PRN no, 'Garmin number', vehicle, current use, Azimuth/Elevation: Edinburgh, Belfast, Manchester, London

 

AOR-E.....120.....33.....Inmarsat3F2.....EGNOS.....195/25-192/27-196/28-199/29

AOR-W....122.....35.....Inmarsat3F4.....WAAS

ART........124.....37.....ESA Artemis.....EGNOS.....148/22-146/22-147/24-149/26

IOR-W.....126.....39.....Inmarsat3F5.....EGNOS.....152/21-148/21-147/22-147/25

IOR.........131.....44.....Inmarsat3F1.....ESTB test..109/4-106/2-109/5-110/7

POR........135.....47.....Inmarsat3F3.....WAAS

 

You can see why we, in the north-west, haven't seen much of the IOR signal since testing began...

[+Team Ullium]

Neatly done Wildlifewriter

 

Though unless there are some budding astronomers out there your table might not make much sense to some .... but having said that it shouldn't be too difficult for them to find the approx co-ords (from their home base) and angle of elevation from your basic information

 

I've taken a copy myself for future reference...thanks mate

 

Ullium.

[+wildlifewriter]

Though unless there are some budding astronomers out there your table might not make much sense to some

Quite right, of course, though in my own defence I suppose that non-techies might find this topic of little interest, anyway.

 

Azimuth: the bearing (in Deg True) on which the satellite lies, from a given location.

Elevation: Angle (in Deg) above an unobstructed horizon.

 

These vehicles are in equatorial (more or less) geostationary orbits, so their bearings do not change - unlike the 'ordinary' GEO constellation.

 

More useless information: the base co-ords used in my calculation were those of: Tower of London; Edinburgh Castle; Belfast Castle; and somewhere in central Manchester that isn't a castle.

 

Viewers in Wales have their own programmes at this time.

[+Team Ullium]

I might have been tempted to complain about the omission of Glasgow (especially Govan !! ) but seeing that I have bagged nearly all the caches in the west and I'm spending more time in the Embra region ... I am well satisfied

 

Ullium.

[+wildlifewriter]

I might have been tempted to complain about the omission of Glasgow (especially Govan !!

A new satellite, designed specifically for operations in Glasgow South, is scheduled for launch on ArianeV during the early part of next year.

 

Designated CU-UR1,2 it will broadcast the same SBAS data stream as other vehicles, but without consonants...

Edited September 2, 2004 by wildlifewriter

[+Team Ullium]

 

Ullium.