Waas

[+Gee Bee]

Does anyone have WAAS enabled on their GPS. Just been to a site and saw this;

 

http://gpsinformation.net/waasgps.htm

 

“This does NOT mean that you can be in England, Mexico, Canada or any other location very distant from the WAAS correction stations and expect the USA WAAS corrections to be useful even if you can receive the WAAS satellites. In fact, if you are in Europe, Africa, Australia or anywhere more than perhaps 500 miles away from the shores of the USA, the use of WAAS signals may well REDUCE the accuracy of your GPS fixes. Europe's EGNOS system (compatible with WAAS but for operation in Europe) is in the test phase now and is transmitting a "do not use" flag. Magellan GPS receivers ignore this flag and use the signal anyway (for what it is worth), but Garmin receivers honor the flag's intent and will not use the EGNOS data as long as the "do not use" flag is set.”

 

I’m intrigued that it mentions that if you have this set it can make a difference to the accuracy of the receiver! Has anyone encountered this problem?

[+sTeamTraen]

I think the key phrase is "even if you can receive the WAAS satellites". AFAIK they are well below the horizon in Europe.

[+Gee Bee]

By having it enabled does it degrigate the accuracy of the GPS in the UK.

[+-Phoenix-]

it certainly degrades the life of your batteries

[+rutson]

it certainly degrades the life of your batteries

Pretty sure that's a Garmin thing.

[+wildlifewriter]

By having it enabled does it degrigate the accuracy of the GPS in the UK.

There have been rumours that it does - but I have never seen any evidence of it, here in Europe.

 

Except in the special case, which might arise like this...

 

i) You own a typical mainstream GPS handheld or recent design. This will have twelve receiver "slots" to handle signals from visible satellites. (or, some models may have fourteen.)

 

ii) With the WAAS facility (compatible with the upcoming European EGNOS system) switched on, two of these slots will be allocated to look for usable signals of that type. Even if no EGNOS (WAAS) satellites are in view, the receiver will go on looking for them.

 

iii) In theory, this could cause a small loss of accuracy, IF there were "ordinary" GPS satellites in view which the receiver could have made use of, with the extra two channels.

 

In theory...

 

... in practical use, we can't usually measure the difference.

 

-Wlw.

[+Team Ullium]

Does anyone have WAAS enabled on their GPS. Just been to a site and saw this;

 

http://gpsinformation.net/waasgps.htm

 

“This does NOT mean that you can be in England, Mexico, Canada or any other location very distant from the WAAS correction stations and expect the USA WAAS corrections to be useful even if you can receive the WAAS satellites. In fact, if you are in Europe, Africa, Australia or anywhere more than perhaps 500 miles away from the shores of the USA, the use of WAAS signals may well REDUCE the accuracy of your GPS fixes. Europe's EGNOS system (compatible with WAAS but for operation in Europe) is in the test phase now and is transmitting a "do not use" flag. Magellan GPS receivers ignore this flag and use the signal anyway (for what it is worth), but Garmin receivers honor the flag's intent and will not use the EGNOS data as long as the "do not use" flag is set.”

 

I’m intrigued that it mentions that if you have this set it can make a difference to the accuracy of the receiver! Has anyone encountered this problem?

First I think it should be noted that the article mentioned was only last updated in July 2002

 

It is nearly three years out of date....also we in the UK don't receive WAAS satellites ... we receive the European equivalent the EGNOS satellite which, when it transmits is no longer in test mode as it was back in 2002 but is in the second best mode (the one which gives 3 metre accuracy) and in a few years time this will be swallowed up by the Galileo project (at which time the mode will increase to give sub metre accuracy).

 

Certainly there would appear to be some truth to the claim that having WAAS switched on in one's GPSr does eat up a little bit more battery life ... but I would not expect it to be so great as to cause much concern. Nor would I see that being only a Garmin issue...Magellan GPSr's are not all that different

 

The proof is in the pudding...I will keep WAAS switched on until I feel it is to my detriment...at the moment when I receive the correction signals it appears to give me better accuracy...until I feel different I see no reason to alter that decision

[+Renegade Knight]

it certainly degrades the life of your batteries

Pretty sure that's a Garmin thing.

It's a Garmin thing. Shutting off WAAS in a Magellan was reported (in a long dead thread) to have no battery effect.

[+Team Ullium]

it certainly degrades the life of your batteries

Pretty sure that's a Garmin thing.

It's a Garmin thing. Shutting off WAAS in a Magellan was reported (in a long dead thread) to have no battery effect.

I'm still not convinced RK

 

No disrespect meant but can you give my more proof than just that it was stated on a long dead thread??

[+The Forester]

The reason why Magellan (in the SporTrack at least) doesn't give the user a documented option to switch off WAAS is that there is no advantage.

 

It doesn't take much more (if any) battery power to listen to 10 + 2 sats than to 12.

 

Also, the cycle time to process a WAAS enabled fix remains 1Hz.

 

On a pair of 2800mA Nimhs, my GPRs will happily give a full day's worth of WAAS data.

 

What really drags the batts down is connecting the RS232 for any extended length of time or running the backlight on high power.

 

On the issue of whether an augmented fix is better than an unaugmented one, I think the case for using WAAS is overwhelming. When you ask those who claim otherwise to show some objectively logged data, they somehow have difficulty.

 

Every time I've checked WAAS fixing on a known point such as a trig or one of the geodetically surveyed points at Forester Towers I've found that the machine does pretty much what it says on the tin (<3m error).

 

Going back to unaugmnented fixing would feel almost as bad as having to go back to the bad old days of SA (or, worse, Transit -- shudder!)

 

Crippling a WAAS-capable machine by switching WAAS off doesn't look like a very clever thing to do. It's bit like taking a couple of spark plugs out of the engine of your car to make it go faster.

 

Cheers, The Forester

using the term "WAAS" to include EGNOS

[+Firth of Forth]

Does anyone have WAAS enabled on their GPS.

No, I don't. No particular reason, except that its not been a problem finding caches - and I have a few under my belt. Taking time to take a number of fixes without WAAS does not appear to have resulted in poor coordinates for caches that I have set either. Perhaps it depends what you want to use your GPS for and the degree of accuracy required?

[+Renegade Knight]

...I'm still not convinced RK

 

No disrespect meant but can you give my more proof than just that it was stated on a long dead thread??

All efforts to search for the thread were dead ends. The Gist (and I think The Forrester covers it) of that thread was that turning it off, didn't turn off the WAAS circuit. So your GPS would not use WAAS to provide a differential correction but it would still use battery power as if it were.

[+The Forester]

If you are going to be diligent enough to take time to take a number of fixes, why not also let your GPSr give you the best fixes it can? Why disable WAAS augmentation of the fixes? What's the point in doing that?

 

Why hobble the horse when you can let it run?

 

Removal of SA was a boon to us all. WAAS is a similarly useful boon to the quality of retail-level GPSr fixing.

 

GC.com expresses co-ords to a resolution of 0.001' of Lat/Long, which is about 2.1 metres at our latitudes. A WAAS augmented fix, without errors such as multipath, has an accuracy of a similar amount (about 3 metres, or better).

 

Why would anyone knowingly reduce the accuracy of a measured fix by crippling their WAAS-capable GPSR?

 

20 years ago I was part of a lobby group of Surveyors who campaigned vigorously and ultimately successfully for the (then) planned SA idea to be abandoned. We worked hard to persuade the USAF, the DoD, Congress and the White House that SA was a dumb idea. NavStar GPS was/is a beautifully engineered piece of work and for it to be dumbed down so stupidly by SA was absurd.

 

WAAS improves the quality of fixing almost as much, proportionally, as the removal of SA did. Let's not throw away our advances. Let's not dumb down our WAAS-capable GPSrs the way TPTB did to us in the bad old days of SA.

 

Let's use WAAS while we are free to do so and while we can.

 

Let's not dumb it down.

 

Cheers, The Forester

[+The Spokes]

Question:- Does enabling WAAS on a E-Trax mean more battery power

YES

Why

Because you cannot use the battery save function while WAAS is switched on. Turning off the battery save mode to enable WAAS means I gobble up batteries at a fast rate.

So although WAAS itself may not cause the batteries to be used up turning off the battery save feature does.

There that is one reason I hobble my horse. To make it live longer.

Edited March 10, 2005 by The Spokes

[+The Forester]

Doesn't your battery pack last long enough to take fixes in normal (ie not battery-saving) mode when placing a cache?

 

How many hours do you get out of your system without using battery save mode? Enough time to log good quality WAAS-assisted fixes to record the position of a cache?

 

What kind of batteries are you using that might cause someone to forego use of WAAS when recording the position of a newly placed cache?

 

Have you considered carrying a spare pair of batteries.

 

Are the people who feel they have to shut off WAAS when measuring the co-ordinates of a newly placed cache perhaps dragging down the batteries by connecting to a PDA? RS232 connections can be quite harsh on current drain.

 

Cheers, The Forester

Perhaps I'm just lucky to have a Magellan, with which it is no problem to operate the GPSr in WAAS mode for 12 hours or more without having to swap out the batteries for a fresh pair.

[+Pharisee]

I currently use two GPSrs..... an Etrex Legend (not the new colour version) and an older GPS III. The Legend is WAAS enabled but to be honest, I very rarely manage to get a 'D' showing in any of the signal strength bars. I use this little device for 'cache hunting' because it's smaller, lighter, prettier and marginally easier to use than the GPS III. I usually turn it off between caches and only turn it on again when I think I'm somewhere close to 'ground zero'. That's probably why I seldom get a WAAS lock, it's rarely on for long enough. I get a good days caching from one pair of NiMH rechargeables.

I always use the GPS III when setting a cache because while it's not WAAS capable, it does have the 'averaging' function that the Legend doesn't. I'll leave it running on a new cache position for about half an hour and get an average of around 1800 separate readings (and satellites move quite a way in 30 minutes). This usually results in a reported error of around 12-15 feet. More often than not this will be repeated on subsequent visits and the two or more results, if different, averaged again. It's rare that anyone reports that my cache co-ordinates are a long way off. This unit does, however, have a prodigious appetite for batteries and a set of 4 NiMH rechargeables don't last very long!!

[+Boneychest & Catsuey]

Does anyone have WAAS enabled on their GPS.

Nope!

 

My Garmin Vista has never indicated a WAAS satellite - I guess due to the 'ignore' flag and so I turn it on occasionally just to check but then turn it off again. No idea about battery life but I know that they run down fairly rapidly when its on the map page.

[+Lost in Space]

It's rare that anyone reports that my cache co-ordinates are a long way off...........

That's because by the time they actually get there they are too knackered to care about GPS readings.........

 

[+Pharisee]

It's rare that anyone reports that my cache co-ordinates are a long way off...........

That's because by the time they actually get there they are too knackered to care about GPS readings.........

 

Ahhh... woken up have you, Neil?

[+Lost in Space]

Ahhh... woken up have you, Neil?

I'm still here - just waiting for a post that is grammatically correct and without any spelling errors.........

[+Team Ullium]

I have the new Garmin Legend C (colour) and reportedly it gives 36 hours constant usage on 2 AA batteries and although I think this might be something of an exaggeratiion, I have so far never had to replace my batteries even after up to three days constant cachying. So it is very much better than any other GPSr I have used.

 

Of course it won't be switched on all the time, but considering I use it in the car to find the car parking co-ords, it gets quite a hammering.

 

So normally I have the GPSr switched on from the moment I set off until I find the cache...with WAAS switched on.

 

Just this last few weeks I also have noticed a marked difference in reception of EGNOS in that I rarely seem to get the 'D's showing but I have put that down to perhaps due to atmospheric conditions which can sometimes take longer to lock on than at other times. So I maybe just haven't had it switched on long enough.

 

Also, I have never needed to use the battery save mode on any GPSr I have owned as the rechargeable's I use give more than reasonable service. So I cannot comment how useful this option would be .... I have always assumed that the battery save option reduced the track points recorded and I was always reluctant to go down that road seeing that I save my tracks to my computer when I get home.

 

But like others I am not all that convinced that this extra EGNOS correction facility is all that necessary for normal geocaching and I have had some amazingly accurate readouts on an 'non WAAS' enabled GPSr in the past so having it switched on all the time at the moment is just to satisfy my curiousity to see if I really can observe any difference

[+Gee Bee]

Probably answered my own question that I posted at the beginning but I thought I would share this info with you and would welcome your comments on this finding;

 

I have a eTrex Legend C (colour), I use NiMh 2300 from Maplins which last about 5 full days of walking/caching at 8 hours per day and that’s with WAAS switched on!

 

I must admit that I hadn’t got a clue up until the past few days what WAAS was. Reading your comments last night got me to thinking! Lets try an experiment. So to day I took a reading with the GPS with WAAS enabled, it was giving an EPE of 8m, with WAAS enabled it gave an EPE of 4m! With WAAS enabled I have got readings from 3 satellites these are 33, 37 and 44 these differ from time to time and the area I’m in. Having looked into it further it seems that at some point the GPS must have downloaded the required almanac for the WAAS to work! See this link and see what you think…………

 

http://www.gpsinformation.org/dale/dgps.htm#waas

 

I think that after my experiment today I think that I’ll leave my WAAS enabled it don’t make any difference to the drain on the batteries I use and I all ways carry with me at least 2 extra pairs for the GPS.

 

P.S. Without getting my destruction book out of the attic what do the D’s mean on satellite acquiring screen mean?

Edited March 10, 2005 by Gee Bee

[+Team Ullium]

Now that is interesting Gee Bee

 

I use NiMh 2400 rechargeables and I couldn't believe the battery life I seemed to be getting .... if you are experiencing a similar battery life then Garmin must have come up with some great new battery life saving technology since their previous units

 

Aslo, the 'D's mean that you are recieving the EGNOS corrections...if you don't see the 'D's then you are not...it's as simple as that !!!

[+Gee Bee]

Sorry about the battery life I got that wrong so my better half says, it’s more like 3 to 4 days including driving………….

 

It’s my fault again!

 

But I do get good mileage out of those batteries though…

[+Learned Gerbil]

So because your GPSr gives an EPE of 4m instead of 8m it must be more accurate? Where were you at the time? The first E is "estimated" the second is "error". A lower EPE means the device estimates that the error is lower. Without knowing more how that estimated error is calculated, it is tempting to think that the hardware may be wired so that the algorythm for estimated error produces a lower figure just becasue WAAS is turned on.

 

You really need to check the EPE at a known reference point, like a benchmark for itto mean anything.

[+Team Ullium]

So because your GPSr gives an EPE of 4m instead of 8m it must be more accurate? Where were you at the time? The first E is "estimated" the second is "error". A lower EPE means the device estimates that the error is lower. Without knowing more how that estimated error is calculated, it is tempting to think that the hardware may be wired so that the algorythm for estimated error produces a lower figure just becasue WAAS is turned on.

 

You really need to check the EPE at a known reference point, like a benchmark for itto mean anything.

A fair comment Learned Gerbil

 

..and one which perhaps once we all have had more experience of using this relatively new facility we will be able to answer with more conviction

 

However, it is a very appealing reasurance to see one's GPSr reporting that you are likely to be within six or seven feet as opposed to six or seven yards ... even if it is arguable

[+The Forester]

EPE should come down with WAAS in use.

 

This is because the augmentation removes most of the random errors such as satellite clock error, ephemeris error, ionospheric error, tropospheric error etc.

 

All EPE (or "accuracy" or whatever your machine calls it) can do is indicate the tightness of the spread of the residuals of the pseudoranges and take into account the geometric dilution of precision. It cannot really tell you how accurate a fix is.

 

My Magellan SporTrak does not even bother to tell the user what the quality figure is when it is using WAAS. The display merely says "WAAS" instead of showing the EPE.

 

With the modern GPSrs, such as the upscale eTrexes, I really don't think battery consumption is a reasonable reason for eschewing WAAS, especially when you are looking for an accurate fix for a purpose such as telling people where a cache is to a precision of the third decimal place of arcminutes of Lat/Long.

 

I think the Old Wives Tale about WAAS reducing instead of improving accuracy has finally died the death.

 

WAAS improves GPS fixing and that's that.

 

I don't think a non-WAAS GPSr should be thrown away and replaced with a new shiny thing for geocaching just for the sake of having WAAS, but if you've got WAAS, then for Goodness sake use it!

 

The "shut up" mentality of crippling a WAAS-capable GPSr by switching off WAAS when making static measurements of position of a location such as a geocache is not a healthy one.

 

The simplest way for the doubters to learn the truth about WAAS for themselves is for them to plonk a WAAS-receiving GPSr on a trig pillar and record their own observations. The OSGB36 co-ords of most trig pillars are available online, as are the resources to make an accurate conversion to WGS84 Lat/Longs in the GC.com standard format of a thousandth of a minute of Lat and Long. There are almost as many trigpoints in the UK as there are caches, so there's plenty to choose from.

 

Cheers, The Forester

[+Firth of Forth]

The "shut up" mentality of crippling a WAAS-capable GPSr by switching off WAAS when making static measurements of position of a location such as a geocache is not a healthy one.

 

Cheers, The Forester

 

It's clearly too soon still for me to post anything in this Forum; I'll go back to the dark side of Hadrian's wall.

[+The Forester]

If you step out into the sunlight, out of the shade of Hadrian's wall, your GPSr will be able to listen the WAAS transmitting satellite(s). If you let it speak to you, it'll even tell you which side of the wall you're standing on!

 

It'll correct most of some errors. That's a good thing, isn't it? That's not something to run away from and hide.

 

Notwithstanding the battery save thing, so long as you have the ability to use the WAAS capability of a GPSr then it makes sense to use it.

 

Cheers, The Forester

[+wildlifewriter]

The "shut up" mentality of crippling a WAAS-capable GPSr by switching off WAAS when making static measurements of position of a location such as a geocache is not a healthy one.

It's clearly too soon still for me to post anything in this Forum; I'll go back to the dark side of Hadrian's wall.

 

Just for the record...

 

...seems to know something about using a GPS receiver.

[+Haggis Hunter]

The "shut up" mentality of crippling a WAAS-capable GPSr by switching off WAAS when making static measurements of position of a location such as a geocache is not a healthy one.

It's clearly too soon still for me to post anything in this Forum; I'll go back to the dark side of Hadrian's wall.

 

Just for the record...

 

...seems to know something about using a GPS receiver.

HERE HERE

[+Team Ullium]

The "shut up" mentality of crippling a WAAS-capable GPSr by switching off WAAS when making static measurements of position of a location such as a geocache is not a healthy one.

An unnecessary comment Forester

 

There is no law that says we should all have WAAS enabled if we don't wish to.... and as I said before I have had some very accurate finds without it!!

[+The Forester]

What is the point of telling the WAAS birds to shut up? Why do it?

 

Is there any benefit to anybody? Any advantage? Is there any intelligent rationale behind the "shut up" mentality of disabling a properly functioning WAAS facility? Why does anybody do it.

 

Why not just let the machine do its best? Why tell it to shut up just because it's giving good data? Why dumb it down?

 

I just don't see the point of dumbing down a fix without any good reason.

 

OK, so there's some kind of minor battery drain issue on some models, but surely when you are logging fixes for some particular purpose, such as measuring the co-ords of a cache, it makes no sense to disable a quality enhancing feature such as WAAS. Just take a spare pair of batteries for the sortie if batteries are a problem.

 

The choice is between good fixing and better fixing.

 

I remember going through all the same arguments with the supporters of SA.

 

Cheers, The Forester

[+Firth of Forth]

You are missing my point completely, which was that if a cacher does not/has not had WAAS enabled on their GPS, it will not/won't have been a hindrance to them in finding or placing caches.

 

I accept that having WAAS enabled can improve accuracy, when it is available, but it doesn't really matter as far as geocaching is concerned. If you are surveying or doing something else requiring very precise coordinates, then it will matter.

 

If I own a V reg car that gets me from A to B adequately, then I don't necessarily need to trade it in for a 05 model to get me there.

 

Once again, I object to the use of the phrase "shut up mentality"; actually, it seems to me (and others apparently) that it belongs to you.

 

Now back to the lighter side of Hadrian's wall.

Edited March 12, 2005 by Firth of Forth