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WAAS ?

Fasterthansid
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Fasterthansid

+Fasterthansid

Posted
Posted

I am based in the U.K and have just bought a garmin gpsmap60sxc unit. Now I'm new to this geocaching and wondered if I should enable the WAAS function or not.

 

Will it give me more accurate information with this enabled or not.

 

Thanks in advance for your input. :laughing:

The Patrician

+The Patrician

Posted
Posted

Personally I don't bother with it.

 

"It is not guaranteed to work, it is not guaranteed to increase accuracy, it is not really able to tell you when it will improve accuracy, when it will have no effect, or when it will make for less accuracy than the normal GPS signal. Under good conditions when YOU ARE OUT IN THE CLEAR AND RECEIVING A GOOD SIGNAL FROM THE WAAS SATELLITE, you should get both improved accuracy and improved position stability. YOU must insure that you have the proper conditions so as to experience the improvement at YOUR location."

 

http://gpsinformation.net/waasgps.htm

 

Also:

 

http://www.gpsreview.net/waas/

 

Regards

 

Neil

Amberel

+Amberel

Posted
Posted
"It is not guaranteed to work, it is not guaranteed to increase accuracy, it is not really able to tell you when it will improve accuracy, when it will have no effect, or when it will make for less accuracy than the normal GPS signal. Under good conditions when YOU ARE OUT IN THE CLEAR AND RECEIVING A GOOD SIGNAL FROM THE WAAS SATELLITE, you should get both improved accuracy and improved position stability. YOU must insure that you have the proper conditions so as to experience the improvement at YOUR location."
But you can say much the same about the standard GPS service. It too isn't guaranteed to work, nor can it tell you how accurate it is.

 

Personally, I can't see any reason NOT to use it.

 

BTW, most Garmin receivers will tell you when they are using the WAAS signal by placing a D at the bottom of the signal bars. If you see this, it is probable that your accuracy will be better and more reliable than without it.

 

Rgds, Andy

keehotee

+keehotee

Posted
Posted (edited)
"It is not guaranteed to work, it is not guaranteed to increase accuracy, it is not really able to tell you when it will improve accuracy, when it will have no effect, or when it will make for less accuracy than the normal GPS signal. Under good conditions when YOU ARE OUT IN THE CLEAR AND RECEIVING A GOOD SIGNAL FROM THE WAAS SATELLITE, you should get both improved accuracy and improved position stability. YOU must insure that you have the proper conditions so as to experience the improvement at YOUR location."
But you can say much the same about the standard GPS service. It too isn't guaranteed to work, nor can it tell you how accurate it is.

 

Personally, I can't see any reason NOT to use it.

 

BTW, most Garmin receivers will tell you when they are using the WAAS signal by placing a D at the bottom of the signal bars. If you see this, it is probable that your accuracy will be better and more reliable than without it.

 

 

What Amberel said. :D

PLus.... WAAS reception seems to be a lot better on my Oregon since the last firmware upgrade (or was it the one before that?)

Plus again - differences in battery life with and without it enabled seem negligible - so I don't see any harm in leaving it switched on?? ;);)

Edited by keehotee
The Patrician

+The Patrician

Posted
Posted

My opinion is that at the very time you need the accuracy (grubbing around in hills, a wood or a town for a cache) is precisely the moment at which WAAS/EGNOS is least likely to be helping you, and may even be degrading the position that the normal satellites are giving.

 

On the other hand searching for geocaches is hardly a life-or-death situation (generally) and there are other errors which are going to be massively larger than the difference between WAAS or no-WAAS it probably matters not a jot whether it's on or off!

 

Personally I get to about 10m from a cache location and then use the Mark 1 eyeball to spot the pile of oddly stacked sticks, suspiciously positioned rock, protruding bin-bag or cuddly toy. It usually works.

 

Anyway I prefer Earthcaches.

 

Regards,

 

Neil

The Patrician

+The Patrician

Posted
Posted

This:

 

http://www.telegraph.co.uk/science/space/7...evastation.html

 

http://tinyurl.com/2u7yqv3

 

"Senior space agency scientists believe the Earth will be hit with unprecedented levels of magnetic energy from solar flares after the Sun wakes “from a deep slumber” sometime around 2013.

 

In a new warning, Nasa said the super storm would hit like “a bolt of lightening” and could cause catastrophic consequences for the world’s health, emergency services and national security unless precautions are taken.

 

Scientists believe it could damage everything from emergency services’ systems, hospital equipment, banking systems and air traffic control devices, through to “everyday” items such as home computers, iPods and Sat Navs."

 

Doomed, we're all doomed! Including the WAAS birds!

 

Crouching in cupboard under the stairs.

 

Regards,

 

Neil

dfx

+dfx

Posted
Posted
But you can say much the same about the standard GPS service. It too isn't guaranteed to work, nor can it tell you how accurate it is.

actually, GPS can tell you how accurate it is. based on satellite geometry and signal strengths, it will calculate and tell you the estimated DOP. of course this is a purely theoretical number and there's a certain chance that your actual accuracy will either be higher or lower than that, but at least you got an estimation.

 

not so with WAAS. either you have a signal or you don't, and when you do, your accuracy may either improve, not change at all or even get worse. but you don't know which or by how much.

 

i would assume that the closer you are to a WAAS ground station, the higher the benefits will be of having a WAAS signal, and the further away you are, the higher the chance will be that the signal may have a negative impact on accuracy. but this is based on my layman's understanding of how WAAS works, so don't quote me on that :D

 

but other than that i agree: just turn it on and enjoy. the chances of having decreased accuracy through it are too low to be of any concern, and the potential increase in accuracy is reason enough to use it. of course, if you want to be really sure, feel free to test it all out yourself: find a usable benchmark and take multiple waypoint readings, over several days, once with WAAS enabled and once without, and then compare the results. oh, and post them here too ;)

Fasterthansid

+Fasterthansid

Posted
  • Author
Posted (edited)

Thanks for all your help guys. I'll do some testing with and without waas and see if there is a difference. Thanks for the info I now understand it a little more than I did before.

Edited by Fasterthansid
Amberel

+Amberel

Posted
Posted
But you can say much the same about the standard GPS service. It too isn't guaranteed to work, nor can it tell you how accurate it is.

actually, GPS can tell you how accurate it is. based on satellite geometry and signal strengths, it will calculate and tell you the estimated DOP. of course this is a purely theoretical number and there's a certain chance that your actual accuracy will either be higher or lower than that, but at least you got an estimation.

I'm well aware of how the DoPs work (in the early days of GPS I spent several years as UK tech support for a GPS chipset manufacturer). What the DoPs can't and don't do is tell you how accurate the position solution is. The DoPs are not expressed as a vector (distance and direction), or even as a distance, they are merely a factor - the higher the number, the less accurate the position solution is likely to be, other things being equal.

 

There is nothing in the system to provide any accuracy measure containing a distance component, which is why the accuracy distances made up by many receivers are downright misleading. Just treat them as arbitrary numbers, not as distances - in this case the lower the number the more accurate it's likely to be.

 

not so with WAAS. either you have a signal or you don't, and when you do, your accuracy may either improve, not change at all or even get worse. but you don't know which or by how much.
If you have a WAAS signal, it is likely you will have an improvement in accuracy. It is unlikely you will suffer reduced accuracy.

 

i would assume that the closer you are to a WAAS ground station, the higher the benefits will be of having a WAAS signal, and the further away you are, the higher the chance will be that the signal may have a negative impact on accuracy. but this is based on my layman's understanding of how WAAS works, so don't quote me on that :lol:
In that case I think you may misunderstand how WAAS works. It does 2 major things. It alerts your receiver to satellites transmitting faulty data, so your receiver can choose to ignore them, and it broadcasts a wide area map of the troposphere so your receiver can allow for distortions in the signal timings.

 

Rgds, Andy

Amberel

+Amberel

Posted
Posted

My opinion is that at the very time you need the accuracy (grubbing around in hills, a wood or a town for a cache) is precisely the moment at which WAAS/EGNOS is least likely to be helping you, and may even be degrading the position that the normal satellites are giving.

The benefits of WAAS extend for a period after you lose the signal.

 

Reason to use WAAS: The accuracy of your position solution is likely to be improved, and very unlikely to be degraded.

 

Reason NOT to use WAAS: I can't think of one.

 

Looks like a no brainer to me!

 

Rgds, Andy

dfx

+dfx

Posted
Posted
In that case I think you may misunderstand how WAAS works. It does 2 major things. It alerts your receiver to satellites transmitting faulty data, so your receiver can choose to ignore them, and it broadcasts a wide area map of the troposphere so your receiver can allow for distortions in the signal timings.

yes, i understand that. but the distortions in the signal are measured by ground stations, aren't they? which means that at those locations, the amounts of distortion will be known with the highest accuracy, while for every point in between the ground stations, they have to be interpolated. which then means the further away you are from a ground station, the more interpolation has to be done, and the less accurate the estimated amounts of distortion for the particular location will be. which again means that in the most extreme cases, interpolation may result in a signal correction parameter that's actually in the opposite direction of what it should be. it's not likely to happen, but possible.

Amberel

+Amberel

Posted
Posted (edited)
In that case I think you may misunderstand how WAAS works. It does 2 major things. It alerts your receiver to satellites transmitting faulty data, so your receiver can choose to ignore them, and it broadcasts a wide area map of the troposphere so your receiver can allow for distortions in the signal timings.

yes, i understand that. but the distortions in the signal are measured by ground stations, aren't they? which means that at those locations, the amounts of distortion will be known with the highest accuracy, while for every point in between the ground stations, they have to be interpolated. which then means the further away you are from a ground station, the more interpolation has to be done, and the less accurate the estimated amounts of distortion for the particular location will be. which again means that in the most extreme cases, interpolation may result in a signal correction parameter that's actually in the opposite direction of what it should be. it's not likely to happen, but possible.

It sounds like you think the ground stations are transmitting differential corrections in a similar way to a conventional DGPS, and that those corrections will be most accurate nearest the ground station. In a conventional DGPS you would be right, because they send corrections to the RECEIVED signal, which includes corrections for tropo and other localised distortion. However, I believe that WAAS data are satellite health data, relative to the TRANSMITTED signal, and do not include corrections for local conditions. Your location relative to the ground station should not significantly affect the improvement.

 

The WAAS also transmits wide area tropo maps so your receiver can calculate the localised distortion.

 

Rgds, Andy

Edited by Amberel
The Patrician

+The Patrician

Posted
Posted

"How does EGNOS work?"

 

http://www.esa.int/esaNA/GGGQI950NDC_egnos_0.html

 

http://en.wikipedia.org/wiki/European_Geos...verlay_Service:

 

"Similarly to WAAS, EGNOS is mostly designed for aviation users which enjoy unperturbed reception of direct signals from geostationary satellites up to very high latitudes. The use of EGNOS on the ground, especially in urban areas, is limited due to relatively low elevation of geostationary satellites: about 30° above horizon in central Europe and much less in the North of Europe. To address this problem, ESA released in 2002 SISNeT, an Internet service designed for continuous delivery of EGNOS signals to ground users."

 

Regards,

 

Neil

Amberel

+Amberel

Posted
Posted

"How does EGNOS work?"

 

http://www.esa.int/esaNA/GGGQI950NDC_egnos_0.html

 

http://en.wikipedia.org/wiki/European_Geos...verlay_Service:

 

"Similarly to WAAS, EGNOS is mostly designed for aviation users which enjoy unperturbed reception of direct signals from geostationary satellites up to very high latitudes. The use of EGNOS on the ground, especially in urban areas, is limited due to relatively low elevation of geostationary satellites: about 30° above horizon in central Europe and much less in the North of Europe. To address this problem, ESA released in 2002 SISNeT, an Internet service designed for continuous delivery of EGNOS signals to ground users."

 

Regards,

 

Neil

Not really sure what the point of that is. We all know that we don't always pick up the WAAS signals. When we do pick them up, we almost invariably get better accuracy than we otherwise would, and when we don't pick them up we are no worse off than we were.

 

I simply don't understand why there seems to be resistance to using it!

 

Rgds, Andy

The Patrician

+The Patrician

Posted
Posted
I simply don't understand why there seems to be resistance to using it!

 

I don't have a resistance to using it, indeed I do use it on occasion (not usually though if I'm geocaching). As I pointed out above, for geocaching purposes I doubt it matters whether it's turned on or not. If I was using GPS to guide a supertanker onto its moorings or land a plane I'd definitely turn EGNOS on! In a wood, on a north facing hillside, in a town it ain't going to be helping you much, if at all (and dare I repeat it, you might, in a rare concatenation of circumstances, be getting a worse fix than otherwise).

 

By all means turn it on. Are you going to find many more geocaches as a result (which is surely the point of the discussion in this forum)? Personally I doubt it.

 

Regards,

 

Neil

keehotee

+keehotee

Posted
Posted
I simply don't understand why there seems to be resistance to using it!

If I was using GPS to guide a supertanker onto its moorings or land a plane I'd definitely turn EGNOS on!

 

If you were reliant on using GPS to moor a supertanker - or any sized ship - I seriously doubt you'd be in the job for long, let alone have a ticket in the first place :D:lol:

GerritS

GerritS

Posted
Posted
I simply don't understand why there seems to be resistance to using it!

If I was using GPS to guide a supertanker onto its moorings or land a plane I'd definitely turn EGNOS on!

 

If you were reliant on using GPS to moor a supertanker - or any sized ship - I seriously doubt you'd be in the job for long, let alone have a ticket in the first place :blink:;)

 

I work on ships and yes GPS is used to more super tankers, it was most likely being used to position the Deep Water Horizon :D .

 

It is used to hold this ship in position within afew Meters as a routine, we we have DGPS another version of WAAS/ EGONS but better :D .

 

The reliance on GPS at is is quite scary yes we do it the old fashioned way as well but GPS keeps sneaking in...

 

As a yachtie it is surprising how many people you read about taking sun/ star sights on Atlantic crossings only to find there only chronometer is the GPS :o

 

Back on topic, caching I have an Oregon and keep WAAS/EGGNOG turned on, is it any use for finding caches? Well I recon it takes me longer to find a cache now than when I had an N95 phone :D

 

With the N95 I knew I was there or there about's and started looking :o . With Oregon I expect it at my feet every time :) , yet it so rarely happens :D

 

This thread made me think how much of my time I spend using GPS it has to be for over 60% of my life GPS is being used, one way or another.

Amberel

+Amberel

Posted
Posted
I do use it on occasion (not usually though if I'm geocaching)
Turning it off and on seems such a waste of effort - you still haven't given the advantage that you must think accrues from turning it off?

 

... dare I repeat it, you might, in a rare concatenation of circumstances, be getting a worse fix than otherwise.
You obviously did dare to repeat it, but it remains as pointless a comment as it was the first time. The measurement of GPS accuracy is a statistical function. With WAAS in operation the accuracy and reliability of the solution is improved.

 

By all means turn it on. Are you going to find many more geocaches as a result (which is surely the point of the discussion in this forum)? Personally I doubt it.

 

It seems quite perverse deliberately to set your instrument to be less accurate and reliable than it might be. If you are setting a cache the position is likely to be more accurate. When finding a cache, if all the satellites are transmitting good data, the improvement is likely to be small enough to make little difference. If a satellite is transmitting faulty data the improvement could be significant. This doesn't happen often, but it does happen.

 

Rgds, Andy

smstext

+smstext

Posted
Posted

i use waas especially now garmin are doing something about it on the oregon device. i can get 14-24ft accuracy without it on but with it on anything down to 7ft but 8-10ft usual with waas running.

JimmerUK

+JimmerUK

Posted
Posted

Am I missing something here?

 

I got my Oregon delivered today and noticed WAAS in the settings. I did a quick search and discovered that it only makes a difference in North America.

 

"Currently, WAAS satellite coverage is only available in North America. There are no ground reference stations in South America, so even though GPS users there can receive WAAS, the signal has not been corrected and thus would not improve the accuracy of their unit."

http://www8.garmin.com/aboutGPS/waas.html

 

So, if I turn on WAAS, based in London, am I actually using EGNOS?

dfx

+dfx

Posted
Posted
So, if I turn on WAAS, based in London, am I actually using EGNOS?

yes, the two systems are compatible to each other and interchangeable.

 

there seem to be some translation issues on the oregon. on my oregon, when it's switched to english, it says "WAAS/EGNOS". when i switch it to german, it only says "WAAS" in the same menu option, even though in the german speaking areas you'd have EGNOS, and not WAAS.

needaxeo

+needaxeo

Posted
Posted (edited)

I simply don't understand why there seems to be resistance to using it!

 

Maybe it's just the simple fact you can turn it on and off in the first place. The existence of an option to disable it almost implies that it's not always either beneficial or benign. Otherwise, why would Garmin disable something that improved the GPSr?

 

(Of course, there might be a perfectly valid answer like "Because they sell handhelds in lots of places where a WAAS service isn't available")

 

But to me it's like those 'turbo' buttons they used to have on the front of PCs in the 486 era. People see the button and wanted to know whether they should switch it on, or in what circumstances they should turn it off.

 

For which the answer is really "never", it's the most pointless button ever. But, pedantically, there were a small number of games that ran too fast on these faster processors, before they got a bit more intelligent about developing software that used timers and so on.

 

Similarly here, I read one site that suggested if your GPSr picks up a WAAS satellite rather than an EGNOS one and its software naively applied the correction data then you're potentially worse off because of that. But that just sounds like really buggy software in your GPSr and the implication is they were too lazy to write it, and so just gave you an off button so you could figure out whether the satellite was the right one or not. I think it's bogus, but it's easy to check which WAAS/EGNOS satellite your receiver is using.

Edited by needaxeo
dfx

+dfx

Posted
Posted
But to me it's like those 'turbo' buttons they used to have on the front of PCs in the 486 era. People see the button and wanted to know whether they should switch it on, or in what circumstances they should turn it off.

 

For which the answer is really "never", it's the most pointless button ever. But, pedantically, there were a small number of games that ran too fast on these faster processors, before they got a bit more intelligent about developing software that used timers and so on.

yes, games are actually the whole reason why the turbo button was introduced. in fact it was first introduced on the intel 286 PCs, which had a higher clock rate than the 8086 CPUs. the 8086 CPUs all had exactly the same clock rate, so quite a lot of games were programmed specifically to run at precisely this speed. the higher clock rate of the 286 messed that up, and that's where the turbo button came into play: it reduced the clock rate to the same as the 8086 CPUs, allowing it to play the older games at the correct speed.

 

after that, the turbo button quickly lost significance.

 

ah, now that was a great chance to show off my smarty pants! and totally off-topic too! :grin:

 

obligatory on-topic comment: yeah i agree, i don't see any reason not to have WAAS/EGNOS enabled either. not that it makes a lot of difference in everyday caching life, but still, no harm done in enabling it.

Amberel

+Amberel

Posted
Posted
Similarly here, I read one site that suggested if your GPSr picks up a WAAS satellite rather than an EGNOS one and its software naively applied the correction data then you're potentially worse off because of that. But that just sounds like really buggy software in your GPSr
No, it's just a buggy site you read that information on :grin: . If you pick up a WAAS satellite instead of an EGNOS one it normally will still improve your GPSr performance.

 

Rgds, Andy

Graculus

+Graculus

Posted
Posted

The 3 satellites shown below all broadcast the EGNOS correction signal and cover the whole of Europe. In the UK you could pick up any of the 3 depending on your view of the southern horizon. Your GPS will show you which one you are receiving by the number 37, 33 or 39 (Garmin GPS units). WAAS and EGNOS are compatible with each other and both provide a correction to the normal GPS satellite signal. If you enable WAAS on the GPS it will allow it to pick up the EGNOS signal too.

 

eg1.jpg

 

Chris

Graculus

Volunteer UK Reviewer for geocaching.com

UK Geocaching Information & Resources website www.follow-the-arrow.co.uk

Geocaching.com Knowledge Books

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