Waas

[+Nellies Knackers]

Only downside is that waas/egnos can't tell you which tree the signal is bouncing off

 

Sorry to tip yellow rain on the fireworks of woodland cachers!

[+Roberts-tribe]

Inspired by this very thread I undertook an experiment in respect of the EGNOS transmissions.

 

First of all, I switched on SBAS on my Emtac receiver ( I don't have a dedicated GPSr yet - just my general purpose iPaq & bluetooth Emtac ) and placed it where it had a clear view of Inmarsat AOE at 15.5W.

 

On running the various GPS apps on the iPaq I saw no indication of any EGNOS signals. They may have been there but I saw no indication ( either using the TomTom GPS utility, the Emtac utility ( which also sets receiver properties like SBAS on and off ) or GPSTuner.

 

So, I then linked the receiver to my desktop instead ( I really like bluetooth ) and fired up Hyperterminal which I set to capture to file. I then let this run for well over an hour ( I was bearing in mind the earlier comment on first time use of SBAS ).

 

I then imported the NMEA data into MS Excel. And guess what? No satellites referenced over PRN 29.

 

So, there are a number of possibilities.

1) That Inmarsat bird wasn't doing EGNOS at that time. So I'll try again some other time.

2) I missed the indicators in the NMEA data that indicated augmentation.

3) The GPSr isn't receiving the signal for some other reason ( line of sight was good ).

4) errr Sirf

 

So my questions are :

 

There was a comment earlier about NMEA and Sirf*. I don't really understand this relationship. Can someone explain?

 

In looking for the received satellite data, I investigated the NMEA sentences. The $GPGSA sentence never listed any sat > 29. Would EGNOS satellites s be listed in this sentence?

 

I also looked at the $GPGGA sentences. One of the references I read indicated that differential data should be reported in this sentence with a Sirf chipset. But the $GPGGA sentences I was receiving had a slightly different structure ( and no differential data ).

 

Sorry if this is going far too technical for some, but I am very interested in how it all works and the online info I've found is contradictory.

 

* Just re-read the thread and Sirf isn't mentioned :eek: . Must have been another thread somewhere

Edited November 17, 2004 by Roberts-tribe

[+Hard Oiler]

My personal experience, having just got back from a trip to the UK from Canada, was that I was fairly consistently getting WAAS/EGNOS in the London area with a 2-3 metre EPE (on a Meridian Gold). Maybe slightly less consistently than in Southern Canada/Northern USA but not too different. Without WAAS EPE's were in the 8-10 metre range. With or without WAAS getting close to caches with the GPSr was about the same experience as in North America - no wild jumps in position - a pretty typical Magellan averaging overshoot - and in most cases was within 10 metres of the hiders coordinates.

 

My previous UK trips were pre EGNOS so this was a fair test. Bottom line is that I can't say the GPSr behaves significantly differently in the UK versus North America, with or without WAAS. Any problems I had were terrain related - effect of tall buildings, deep valleys, heavy tree cover - and that's the same wherever you are.

[+The Forester]

The parameters (numbers which represent the degrading factors of the ionospheric and tropospheric and clock error crap) for each particular satellite will of course be different because they are hurtling across the sky (and consequently experiencing different conditions)

 

WAAS (or EGNOS) not only looks at and describes the error for each individual satellite, it also does so for each individual place within the wide area which is covered by the augmentation service. It presents you with a best approximation for the pseudorange raypath correction for each satellite at your reception locale.

 

The reception conditions in Govan are seldom (if ever!) identical to those in Germany, Gibraltar or Gerona. EGNOS takes this into account and divvys up the coverage area into individual bins (pixels, if you like) and transmits what amounts to the equivalent of a current weather forecast for each locale.

Edited November 18, 2004 by The Forester

[Highnoon25]

For those of us across the pond and travel often to the UK, What kind of GPS accuracy can we expect in the UK?

[Trudge]

..

Edited November 18, 2004 by Trudge

[+Team Ullium]

For those of us across the pond and travel often to the UK, What kind of GPS accuracy can we expect in the UK?

A very difficult question to answer Highnoon25

 

I would imagine that there would be very little actual difference in perceived reception given similar circumstances....taking into account such factors as high buildings, hills or tree cover interference!! Not to mention the quality of the equipment used and the type of aerial installed (in reference to the general belief held that the quad helix behaves better under tree cover than some other aerials).

 

Even without WAAS/EGNOS reception I am well satisfied with the functionality of my own GPSr's...so I really don't think you need worry about operational accuracy being any different from what you are used to!?

 

Ullium.

[+snaik]

Have a new GPS which has WAAS, EGNOS and it seems to prefer using SWAG data.

 

Scientific Wild A**** Guess

 

[+Team Ullium]

.....The reception conditions in Govan are seldom (if ever!) identical to those in Germany, Gibraltar or Gerona. EGNOS takes this into account and divvys up the coverage area into individual bins (pixels, if you like) and transmits what amounts to the equivalent of a current weather forecast for each locale.

It is a well known and established phenomenon that Govan gets far more weather than any other part of the UK .... never mind the rest of Europe!!

 

 

Ullium.

[+Pharisee]

.....The reception conditions in Govan are seldom (if ever!) identical to those in Germany, Gibraltar or Gerona.  EGNOS  takes this into account and divvys up the coverage area into individual bins (pixels, if you like) and transmits what amounts to the equivalent of a current weather forecast for each locale.

It is a well known and established phenomenon that Govan gets far more weather than any other part of the UK .... never mind the rest of Europe!!

 

 

Ullium.

Just been speaking to my workshop Foreman, Alex. It seems that he was born "on Govan Hill". According to him... if I've mentally translated his utterings correctly... it's the best place in the world. Apparently it's where Ibrox Park is located (that sound like a good place to put a cache, Bill) the home of Glasgow Rangers (whatever Scout Troop they are). If it's that good, I may come for a visit after all

[+The Forester]

It is a well known and established phenomenon that Govan gets far more weather than any other part of the UK

and then you send your surplus rain and clag onwards towards Embra!

 

A former Clydeside welder once said that when a wally dug in Govan lifts its hind leg at a lamp-post, the citizens of Embra get it in the face.

[+The Forester]

For those of us across the pond and travel often to the UK, What kind of GPS accuracy can we expect in the UK?

Almost exactly the same as in the US.

 

The orbital plane of the satellites is about 55°, so for places North of that Latitude a NavStar fix is not quite so well conditioned as in the lower 48 of the ConUS, but you won't notice the difference for geocaching purposes.

 

The European flavour of WAAS (called EGNOS, though your GPSr will switch seamlessly over to EGNOS from the North American equivalent) is supposedly slightly more accurate than the US WAAS, but you certainly won't notice the difference in the field.

 

The Euro EGNOS is still in the "testing" phase, so you cannot depend on it to be operational 24x7, but it is usually there for most of the time.

 

Mapping in the UK is slightly better than the US. Click on the Streetmapping.co.uk link on a UK cache description page to view an online version of the excellent 1:50,000 Landranger Ordnance Survey map (UK equivalent of the USGS quads). The best paper maps in Britain for rural geocaching are the 1:25,000 Explorer series. They are available from most good bookshops.

 

Cheers, The Forester

[+Haggis Hunter]

It is a well known and established phenomenon that Govan gets far more weather than any other part of the UK

and then you send your surplus rain and clag onwards towards Embra!

 

A former Clydeside welder once said that when a wally dug in Govan lifts its hind leg at a lamp-post, the citizens of Embra get it in the face.

Possibly a very true note, who knows??

 

I guess though that you have said in previous threads that you live in between Edinburgh & Glasgow, [...Edited by Lactodorum to prevent any offence....]???

 

Edited November 18, 2004 by Lactodorum

[+Team Ullium]

A former Clydeside welder once said that when a wally dug in Govan lifts its hind leg at a lamp-post, the citizens of Embra get it in the face.

 

I think HH it was a reference to the prevaling wind coming from the West....usually hitting Govan at 100 mph plus

 

It is especially noticable when the pubs close and all the sober (who am I kidding?) patronage attempt to make their way home to a very warm reception from their nearest and dearest (the reference to 'dearest'...is not one of cost BTW !!).

 

They can be seen leaning over at incredible angles...apparently defying the laws of gravity....but this is solely due to the force of the wind...nothing else I assure you

 

Ullium.

[+The Forester]

HH's latest sneering ad hominem attack is particularly vile. I hope he withdraws it very quickly.

 

This forum is much too pleasant a place to carry such disgusting posts.

[+Eckington]

Now then peeps!

 

Being a non-techie I stopped reading this thread a time ago, as I only understood about 1 word in 3

 

But a quick glance to see how it is going tells me that one or two of you might well be construed as being just a teeny bit, shall we say "parochial"........

 

.........hows about getting back to the interesting stuff?

[+snaik]

Pistols at dawn! Gentlemen on neutral, ground!

 

[+Team Ullium]

Pistols at dawn! Gentlemen on neutral, ground!

 

I suppose you meant 'WATER' pistols Snaik?

 

In that case.... can I suggest a litmus test of the ammunition

 

I wouldn't want anyone to get p ssed off!?

 

 

Ullium.

[+The Forester]

hows about getting back to the interesting stuff?

Who posted the most recent on-topic post?

 

Who dragged the thread off-topic with a scatological reference which sneeringly denigrated a fellow geocacher's home?

 

Why?!

[+Flyfishermanbob]

And so to summarise :-

 

There are those who believe Waas is the bogs dollocks and you shouldn’t leave home without it .

 

There are those who believe Waas will be the bogs dollocks and will use it when its reliable. ( me )

 

There are those who believe Waas is neither here nor there.

 

There are those who believe this thread has run its course;is getting too personal and should be closed. (And they are being very generous ….as they could have done just that )

 

So .. Deva Duo time to go to the bottom of the screen and look at “ moderators options “ …select close thread ....... everyone had had their say ....and I cant see any added value from the tone of recent additions ....

 

regards FFB

[+The Forester]

There are those who believe Waas is the bogs  dollocks  and  you shouldn’t leave home without it .

There are those who are scientifically interested in WAAS.

 

There are those who are not.

 

Some who are interested in the difference between science and superstition may like to look at actual hard data.

 

There's an interesting site which appears to have obtained some data which matches quite nicely with that interest.

 

http://users.erols.com/dlwilson/gpswaas.htm

 

It shows us what WAAS can do for those who are interested in the difference between truth and non-truth.

 

The rest will just shun.

[+Team Ullium]

There are those who believe Waas is the bogs  dollocks  and  you shouldn’t leave home without it .

There are those who are scientifically interested in WAAS.

 

There are those who are not.

 

Some who are interested in the difference between science and superstition may like to look at actual hard data.

 

There's an interesting site which appears to have obtained some data which matches quite nicely with that interest.

 

http://users.erols.com/dlwilson/gpswaas.htm

 

It shows us what WAAS can do for those who are interested in the difference between truth and non-truth.

 

The rest will just shun.

I think we all agree that WAAS/EGNOS will give our GPSr's an increase in accuracy....I don't think anyone is/was denying that....the moot point seems to be ... is it giving this accuracy while in this test mode phase prior to be fully operational ??

 

.... as there seemes to be some doubt about whether this is the case or not!!!

 

Also, even if the EGNOS satellite, we in the northern hemisphere can occasionally get a fix on, is transmitting spot on data for our GPSr's to receive....is it wise to leave this option switched on continually...seeing that the transmissions are not for the moment continuous ??

 

.... meaning does leaving the WAAS option switched on use up one of the GPSr channels thus reducing the number of channels available for normal satellite reception and thereby reducing the effectiveness of one's GPSr by some fraction!!!

 

Ullium.

Edited November 18, 2004 by Ullium

[+Haggis Hunter]

It is a well known and established phenomenon that Govan gets far more weather than any other part of the UK

and then you send your surplus rain and clag onwards towards Embra!

 

A former Clydeside welder once said that when a wally dug in Govan lifts its hind leg at a lamp-post, the citizens of Embra get it in the face.

Possibly a very true note, who knows??

 

I guess though that you have said in previous threads that you live in between Edinburgh & Glasgow, [...Edited by Lactodorum to prevent any offence....]???

 

My sincere apologies, to anyone who was offended by the word that I had used, perhaps I should have left it at filtered??

 

Who dragged the thread off-topic with a scatological reference which sneeringly denigrated a fellow geocacher's home?

 

Why?!

 

I had thought you were trying to do the same to my home town, with the second inuendo to Edinburgh, which in fact had nothing to do with the current topic.

Of coure Forester, dragging a thread off of topic is something that you would never dream of!!!

 

My sincere apologies to Deva Duo, for doing such an act.

[Lactodorum]

OK folks, let's forget the relative merits of various Scottish domiciles and stick to the joys of WAAS.

 

If anyone can tell me how I can use WAAS to stop me falling down muddy banks, getting pricked half to death in gorse and holly bushes, getting stung by indignant wasps and other such "enjoyable" experiences they'll go up in my estimation.

[+Haggis Hunter]

OK folks, let's forget the relative merits of various Scottish domiciles and stick to the joys of WAAS.

 

If anyone can tell me how I can use WAAS to stop me falling down muddy banks, getting pricked half to death in gorse and holly bushes, getting stung by indignant wasps and other such "enjoyable" experiences they'll go up in my estimation.

My apologies, nothing other than WAAS will be mentioned by me again

 

I would say switch it on and make sure that whilst you are using the GPS with WAAS/EGNOS enabled, remember to look around for all of the hazards, it works for me

[Lactodorum]

remember to look around for all of the hazards, it works for me

Look around!!! I hadn't thought of that I spend all my time watching the little arrow

[+The Forester]

if 8 satellites were more than enough then why do the sellers make a big deal of their products having 12?

Maybe it's a bit like the manufacturer of my car telling me that it's got a top speed of 109mph.

 

I don't think they are telling me that I will ever drive at 109mph: only that my machine has capabilities which can meet my maximum needs and still have surplus capacity.

 

Nevertheless, I would prefer to have a 12-channel parallel reciever in my GPSr than a 5 or 8 channel one.

 

The more pseudorange data -- the better. You can always knock out a duff Line Of Position (LOP) either in realtime or in post-processing.

 

One of the things which WAAS is supposed to do (and does) is identify a rogue NavStar sat which is transmitting duff data. It's part of the original FAA specification and intent of the LAAS/WAAS systems. WAAS equipped GPSrs knock out the identified duff LOPs for you.

 

DGPS does something similar to WAAS, but on a more local basis and needs more operator input in implementation by the active user to deselect a duff LOP.

 

Remember that WAAS is originally intended to be used by very busy airline pilots to make precision "blind" approaches to runways at much higher speeds and with rather more accuracy than some of us make our approaches to some geocaches. That's why the certification standards for WAAS (and the EU equivalent EGNOS) are so stringent. That's why the accuracy of the system is so much better (when it works!) than an unaugmented GPS fix.

 

Cheers, The Forester

[+Team Ullium]

if 8 satellites were more than enough then why do the sellers make a big deal of their products having 12?

Maybe it's a bit like the manufacturer of my car telling me that it's got a top speed of 109mph.

 

I don't think they are telling me that I will ever drive at 109mph: only that my machine has capabilities which can meet my maximum needs and still have surplus capacity.

 

Nevertheless, I would prefer to have a 12-channel parallel reciever in my GPSr than a 5 or 8 channel one.

 

The more pseudorange data -- the better. You can always knock out a duff Line Of Position (LOP) either in realtime or in post-processing.

 

One of the things which WAAS is supposed to do (and does) is identify a rogue NavStar sat which is transmitting duff data. It's part of the original FAA specification and intent of the LAAS/WAAS systems. WAAS equipped GPSrs knock out the identified duff LOPs for you.

 

DGPS does something similar to WAAS, but on a more local basis and needs more operator input in implementation by the active user to deselect a duff LOP.

 

Remember that WAAS is originally intended to be used by very busy airline pilots to make precision "blind" approaches to runways at much higher speeds and with rather more accuracy than some of us make our approaches to some geocaches. That's why the certification standards for WAAS (and the EU equivalent EGNOS) are so stringent. That's why the accuracy of the system is so much better (when it works!) than an unaugmented GPS fix.

 

Cheers, The Forester

Gee Forester...I had a bit of a job tracking back to find that comment of mine you quoted there

 

And I think it was obvious from the reply from which you snipped that comment that I was implying that as far as channels are concerned ... the more the merrier for all the reasons you have highlighted there

 

But what happened to my more recent comments ???

 

I still feel you are avoiding the real issue here

 

Ullium.

[+The Forester]

I still feel you are avoiding the real issue here

My understanding of the real issue here is: "Is WAAS available in the UK?"

The answer to that question is yes.

 

Sub-issues are whether an augmented fix is more accurate than a non-augmented fix and whether it is worth switching the WAAS capability on in a suitable GPSR.

The answer to both of those questions is yes.

 

I've looked at a lot of augmented data and I haven't yet seen any which contraindicates the fact that a currently augmented fix is better than an unaugmented one.

 

A year or so ago, the situation with EGNOS wasn't nearly so clear as it is now. Nowadays EGNOS is pretty good. It's very nearly good enough to guide the autolanding of an airliner with hundreds of pasengers onto a foggy runway. That's certainly good enough to go geocaching with!

 

A further sub-issue is whether an accurate GPSr is useful when going after a cache which has dodgy published co-ordinates. I think the answer to that question is yes, but perhaps it would be better if we help those cache-placers to learn how to assess the quality of a GPS fix. Too many people just look at the numbers without having the faintest idea of what they actually mean and are therefore unable to make a sensible judgement with them.

Edited November 21, 2004 by The Forester

[+Snosrap]

...and I still can't dadgum well get it! The occasional grey bar is the nearest I've yet seen.

 

So as far as I am concerned the answer to the question posed by this thread is "only in certain places, at certain times and with certain equipment."

[+snaik]

OK now three pages on this thread!!

 

How do you! pronounce WAAS!!!

 

[+perth pathfinders]

Isn't it pronounced ..

 

W Aaaaaaaaaaaagh S

 

[+The Forester]

"only in certain places, at certain times and with certain equipment."

All true!

 

Of course you need a waas-enabled GPSr. That pretty much goes without saying.

 

Of course you need to be in a place which has a good line of sight to either of the two InMarSat relay satellites.

 

Most of the time the EGNOS service is being transmitted from the East Atlantic satellite which is the one closest to us in the UK. The Indian Ocean one is much too low on the horizon for many of us in Northern and Western Britain and the Artemis satellite isn't yet ready for service as they had a bit of a whoopsie during launch and it has taken many months for the engineers to coax it into a useful orbit.

 

I think it's fair to say that WAAS is available to us most of the time. It's considerably more reliable than it was earlier this year which is why so many airlines are equipping their jets to make use of the service.

 

Eventually, in theory at least, conventional instrument landing systems and some en route navaids will be abandoned in favour of WAAS and LAAS systems. When you consider the accuracy needed to keep a large airliner such as a Boeing 747 or Airbis A380 close to the centreline of a runway, you can see that this is a sytem which is designed for very high precision and relibility. If it was safe, accurate and reliable, I very much doubt whether they'd find many pilots willing to use it in reduced visibility landings and takeoffs. Pilots tend to be a conservative lot and they tend to be risk-averse. Persuading them to use WAAS/LAAS needs the very highest standards.

 

ESA's got a fair way to go in the project, but they're getting there.

[+Haggis Hunter]

A year or so ago, the situation with EGNOS wasn't nearly so clear as it is now.

I'm glad you didn't try to explain it a year ago, as my head is like scrambled eggs at the moment, dread to think what it would be like before it was made as clear as it is now.

[+Team Ullium]

I think we all agree that WAAS/EGNOS will give our GPSr's an increase in accuracy....I don't think anyone is/was denying that....the moot point seems to be ... is it giving this accuracy while in this test mode phase prior to be fully operational ??

 

.... as there seemes to be some doubt about whether this is the case or not!!!

 

Also, even if the EGNOS satellite, we in the northern hemisphere can occasionally get a fix on, is transmitting spot on data for our GPSr's to receive....is it wise to leave this option switched on continually...seeing that the transmissions are not for the moment continuous ??

 

.... meaning does leaving the WAAS option switched on use up one of the GPSr channels thus reducing the number of channels available for normal satellite reception and thereby reducing the effectiveness of one's GPSr by some fraction!!!

 

And you are still avoiding the REAL issue which is on most cachers minds at this monent in time ???

 

Which makes me wonder if your possible answer might be that you really agree with my own thoughts (and some others as well) on THIS issue...and that is leave it deselected until it is up and running properly

 

Ullium.

[+Snosrap]

Isn't it pronounced ..

 

    W  Aaaaaaaaaaaagh S

 

I think W'ARSE might be more appropriate!!

[+Haggis Hunter]

I think W'ARSE might be more appropriate!!

Woops, better watch out as I mentioned the word that comes out of that, and I upset some people, and got my entry edited.

[Abominable Abomnible]

Waaaasup!!

 

AA

[+Team Ullium]

Yes I can see that this thread is not that interesting for some peeps....but how about just ignoring it?...instead of hyjacking it and attempting to turn it into a fun thread...there is plenty enough on the forum....leave this one to people who really want to learn something!!

 

Sorry about the rant....no offence meant

 

Ullium.

[+badger]

Being a newbie to this and not wanting to read the full thread (read lazy!), can anybody explain in laymans terms what WAAS and EGNOS are?

I use a Garmin Etrex Legend, which can use WAAS.

Thanks in advance

Matt

[+wildlifewriter]

Which makes me wonder if your possible answer might be that you really agree with my own thoughts (and some others as well) on THIS issue...and that is leave it deselected until it is up and running properly 

Bill,

 

It might be a mistake to assume that there's a "right" or "wrong" answer to this. As I said (about 2 pages back) it's really a matter of making an informed choice.

 

I can envision a time coming when you (or I) will be watching our GPS indicator as it points to the middle of a large lake. Instead of saying:

"Looks like someone used the wrong map datum for this cache"

...it'll be:

"Looks like someone got a load of duff EGNOS corrections for this cache".

 

This is commonly referred to as The March Of Progress...

[+Team Ullium]

Thanks Wildlifewriter

 

Mark you .... given that if quite a number of GPSr users from the Rambling forum and elsewhere seem to think that ... for the moment anyway....the signals are not to be trusted all the time....then this would be an excellent reason for leaving it switched off ??

 

But even if that supposition is totally wrong....and the signals we get (when we can get a fix that is) are 100% spot on and gives us greater accuracy....does it not reduce our existing channel availability by one when we have it switched on and we are not receiving the correction factor?? Not to mention giving the internal processor an extra task in polling for reception it can't get ??

 

If either of these statements holds water ... then surely it is not purely a matter of personal choice...like choosing a brand of walking boot?? But more a matter of implementing a sensible precaution ??

 

Of course I am more than willing to admit I might be missing something here that yourself and Forester can see ... and I don't

 

Ullium.

[+The Forester]

does it not reduce our existing channel availability by one when we have it switched on and we are not receiving the correction factor?? Not to mention giving the internal processor an extra task in polling for reception it can't get ??

...

I might be missing something.

Ullium,

 

You're a competent mathematician. Calculate the increase in accuracy you would obtain by having 12 sats instead of 11. Then look at the improvement in accuracy which you obtain by using 10 or 11 augmented satellite lines of position. I'd say the case for augmentation is overwhelming. That's why so many commercial user spend lots of money to buy WAAS/LAAS/DGPS systems for diverse applications like aviation, shipping and Survey work.

 

On the polling time issue, modern GPSrs, even the wee cheapies, mostly tend to be simultaneous receivers. It's not like the old days of 5 channel serial receiver when the wee beastie had to listen to each satellite in turn. Your modern receiver is listening to all 12 sats at the same time. They are all transmitting on exactly the same L1 frequency at the same time and your receiver sorts out the signals almost instantaneously.

 

The processor overhead issue won't affect us at the speed we walk! A GPSr is quite quick enough to produce timely updates for jet aircraft and speeding missiles. The fix update rate which our little handheld GPSRs produce is quite fast enough for us on foot or in a car -- even with WAAS!

[+Team Ullium]

Forester:

 

Calculate the increase in accuracy you would obtain by having 12 sats instead of 11. Then look at the improvement in accuracy which you obtain by using 10 or 11 augmented satellite lines of position. I'd say the case for augmentation is overwhelming. That's why so many commercial user spend lots of money to buy WAAS/LAAS/DGPS systems for diverse applications like aviation, shipping and Survey work.

 

I never at any point disagreed with you there....yet you still keep making this point?? We must have our wires crossed somewhere

 

On the polling time issue, modern GPSrs, even the wee cheapies, mostly tend to be simultaneous receivers. It's not like the old days of 5 channel serial receiver when the wee beastie had to listen to each satellite in turn. Your modern receiver is listening to all 12 sats at the same time. They are all transmitting on exactly the same L1 frequency at the same time and your receiver sorts out the signals almost instantaneously.

 

With a single processor there is no such animal as parallel processing....only psuedo parallel processing....of course commercial outlets don't like to highlight this fact of life....to achieve true parallel processing one requires multi-processors!

A single processor can only work on one piece of information at a time....it may give the appearence of multi-tasking....but that is all...just the appearance.

 

I could be wrong (and I could find out if I had the time and energy) but I rather imagine that the power of the processors in GPSr units wont compare to the normal PC processor and given it is running a complex 'real-time' program (a program which does not necessarily require the input of a human!) and has to continuously poll (send out a request for information) several possible sources of information in order to compute a ongoing result....it is no surprise to learn that the less it is asked to do...the better it functions!!

(This is why letting too many of those little stay resident programs, which run in the background on one's computer, get out of hand as they seriously slow one's computer down to a crawl.)

 

So where I agree that these GPSr processors do a marvellous job....there are limits and when one considers that the computation of location is just one of the many 'real-time' tasks the processor has to do....in principal the more we can ease it's task the better! But I appreciate the point you are making...and concede that the actual improvement in processor speed will probably be minimal....even so the principle of what I'm saying stands.

 

The processor overhead issue won't affect us at the speed we walk! A GPSr is quite quick enough to produce timely updates for jet aircraft and speeding missiles. The fix update rate which our little handheld GPSRs produce is quite fast enough for us on foot or in a car -- even with WAAS!

 

If that were the only consideration I would totally agree with you....however trying to compare a fully commercial global positioning unit which is specifically purpose built for aircraft navigation....with what we use in the field....is certainly not comparing like for like....would you as a competent pilot through out the unit built into your plane and use .. say...a Garmin eTrex??? Enough said eh?

 

Everone has experienced the fact that even at our slow walking speed ... we have to wait for our units to catch up on occasion...so I don't think your point there is valid.

 

So in closing....nothing that has been said on this subject so far has convinced me that ... on the odd occasions when EGNOS is transmitting and on the even odder occasions when it can be picked up by our GPSr's ... that the corrected information transmitted can be relied upon 100% at this moment in time!

 

So I will wait until it is fully up and running before leaving it switched on continuously

 

Ullium.

Edited November 22, 2004 by Ullium

[+wildlifewriter]

(snip) So in closing....nothing that has been said on this subject so far has convinced me that ... on the odd occasions when EGNOS is transmitting and on the even odder occasions when it can be picked up by our GPSr's ... that the corrected information transmitted can be relied upon 100% at this moment in time!

 

From the last ESTB bulletin available (Friday's)...

* from 17/11/2004 00h42 UTC to 17/11/2004 00h54 UTC : no broadcasting, then message without differential corrections.

Just a little glitch, there....

[+Team Ullium]

Just a little glitch, there.... 

 

Stirrer!!

 

 

Ullium.

[+snaik]

 

Clears throat for this one!!

 

[JackiePenn]

(snip) So in closing....nothing that has been said on this subject so far has convinced me that ... on the odd occasions when EGNOS is transmitting and on the even odder occasions when it can be picked up by our GPSr's ... that the corrected information transmitted can be relied upon 100% at this moment in time!

 

From the last ESTB bulletin available (Friday's)...

* from 17/11/2004 00h42 UTC to 17/11/2004 00h54 UTC : no broadcasting, then message without differential corrections.

Just a little glitch, there....

missed this bit

 

* from 19/11/2004 00h00 UTC to 19/11/2004 04h16 UTC : Iono corrections unavailable.

[+Haggis Hunter]

 

Clears throat for this one!!

 

Now Now Snaik some people would prefer it if we could keep the humour to other threads.

[+The Forester]

from 19/11/2004 00h00 UTC to 19/11/2004 04h16 UTC : Iono corrections unavailable.

How many geocachers were honestly inconvenienced by not having ionospheric corrections between midnight and 04:16 last Saturday morning??

 

The rest of us who know how to use WAAS were not.