Kerry.

Geo, Don't think that plot has much to do with WAAS accuracy but more to do with the "affect of WAAS on accuracy" when WAAS is enabled outside the intended ground coverage area. Cheers, Kerry.

Same here with the "typical" can attain accuracies of 1-3 meters. Especially when inexpensive 'averaging' GPS units actually have some general precision issues displaying less than 3 metres. Again many quote GPS accuracy as X metres but forget the important bit, the type/confidence of those metres. Cheers, Kerry.

Yeah right Yeah right Geo, are you going to start all this waffle again Cheers, Kerry.

GPS SPS Global average positioning domain average is < 13 metres @ 95% horizontal and < 22 metres vertically. WAAS was designed for 7 metres @ 99% and hence is about 5 metres 95% and 3 metres CEP. Most of the real time monitoring that is done for WAAS purposes is in the vertical as that's the most critical thing that aircraft are concerned with. As for differential systems, including WAAS, dGPS etc it's the integrity and error monitoring of the position that is more important than straight/pure accuracy. As far as geoid models are concerned they are simply models that define the interpolated separation distance (~vertical) between GPS ellipsoid heights and orthometric (sea level) type heights. They have absolutely nothing to do with determining initial GPS type coordinates XY or Z. Cheers, Kerry.

GPS (recreational) accuracy within centi-metres, then obviously some don't have any understanding exactly what recreational GPS accuracy is, actually what accuracy is at all. Averaging and actual recreational GPS accuracy aren't in any way even related. Since I really didn't make specific mention of this 10 times more accurate, then perhaps you'd like to specify the official accuracy spec for both GPS and WAAS. Geoid model? come on what's a geoid model got to do with GPS accuracy? Cheers, Kerry.

Not totally correct. Global WAAS? not any time soon or even any time latter. Also Raytheon are only the primary contractors and actually got the job by default and aren't the initial contractors awarded the project. Cheers, Kerry.

As with any GPS/WAAS type accuracy figure simply stating so many metres really doesn't mean anything at all. Also what might be currently being achieved has really nothing to do with the actual accuracy specification of the system. 3 metres appears to be a favourite quote but where did that figure actually originate from and exactly what sort of 3 metres are they. Cheers, Kerry.

6 seconds Yes, very tight but very few receivers yet have certification to meet this requirement and certainly not any of the recreational handhelds. I suppose one could say with dGPS that erroneous satelitte gets trapped even before transmission. comes down to about 1 metre per 150 miles (from memory)

GPS time as against GPS timing, two completely different things. GPS "clock" simply tells/shows the time and is not a critical function of a GPS and hence doesn't have priority as far as CPU processing is concerned. Basically some units can be up to and around 2 seconds behind as far as knowing when lunch time is and yes it is basically controlled through the nav mesagge data. Cheers, Kerry.

Actually I can imagine, the WAAS Geo's can in fact be included in the determination of the position solution and can basically mirror the measurement function similar to a GPS satellite but more like a pseudo satellite. This is a WAAS option, does exist but hasn't seen a lot of activation in everyday useage. Cheers, Kerry.

Blah, blah........ Yes another year, appears now no different to the previous as for a moment there (just for a moment) one might have expected to see the last of the 1 foot, 2 feet, 3 feet accuracy (er sorry 3 feet estimate) rubbish, no doens't appear so. But then of course then there's auto-averaging Cheers, Kerry.

Shouldn't that read "What's your best accuracy ESTIMATE figure" Cheers, Kerry.

Fizzy, one would have thought that's what differential systems are supposed to do, detect the problems, lets face it both are differential systems and both are supposed to eliminate the bad data, that's what they do. Which recreational receivers have the capability of using all the error capabilities and alarms? Cheers, Kerry.

Both are compatible Wide Area Differential GPS (WADGPS), both work the same way just that the corrections are based on different ground stations. In Europe EGNOS = WAAS, just a different name and operated/provided by different organisations. Cheers, Kerry.

WAAS specifically No, but EGNOS is the European version that should? give coverage in the UK. Cheers, Kerry.

Probably out of luck and if verison 2.XX then definately out of luck, apart from as I believe there being no updates I don't believe it was even possible given the type of 16 bit processor used. This was also a general problem with much of the garmin 12 family. Even though there are updates available for say a 12XL one could not upgrade if it was version 2.XX either. Cheers, Kerry.

Really about all that changed on July 10, 2003 was a change to message type 2 (normal Geo mode). Apart from including the new GPS launches into the WAAS mask there really wasn't anything done that magically improved operation going from message 0 to 2. Leave the update with me, will have to see who has what available that will fit the purpose. Cheers, Kerry.

Fizzy, actually then you'd have to complain to all manufacturers but then apart from any "suspected" issues with software all receivers that come into Oz have WAAS disabled, that simply have to. We've had quite a bit of discussion with some distributors (specifically in the marine field) in Oz about avertising WAAS type systems and their reason? Australian boatbuilders build boats for export, yeah right, so what. Then of course there's they mention MTSAT, yeah sure what about MTSTAT? No really I think people have to take WAAS in their own particular area on face value and base their decisions if it is effective or not on experience. Of course the powers are going to push the virtues of a still yet to be (fully) completed 5-6 billion (US$) system and if it hadn't been at the insistance of the DoT (specifically), it was looking as if the FAA might have kept it in test mode. 5-6 billion is a hell of a lot to justify to congress for a system that only effectively covers CONUS and some fringe areas. Some have to realize that it's not the end and be all of augmentation systems, it has limitations and people do need to realize this. Cheers, Kerry.

Fizzy, this example and note that without going into all the little nitty bit and pieces that make it all technical sounding this is what one actually gets in practice, that is everyday use. Haven't really seen a receiver do much different over here, and that includes many different makes and many of these are far and away above recreational receivers. But if you've got a receiver that you think will do different then feel free to send it over as Oz is quite a good place to test this type of stuff, probably better reception from POR than even in the US and very much out of the correction area. However one big problem with many manufacturers now is they are shutting the recpetion loophole for units outside the intended ground coverage, guess why? Frankly, if WAAS did it half as well in Oz as you expect it might (and it doesn't) then some certain companies would be pushing there "pin point accuracy stuff" for all it's worth, but they don't, they can't as that's what would be called false advertising and what might even surprise you even more thay actually realize that. Cheers, Kerry.

Fizzy, that is rubbish and talking about learing then it might pay to realize that WAAS used outside the "intended" correction area can/does/will actually make accuarcy worse, in some cases much (much) worse. This is one of the reasons why most manufacturers have now restricted the area where corrections are valid due to the possible cross over between EGNOS and WAAS Geo's. As for this 10 minutes of data every whatever, the "real" WAAS corrections have an error delay of around 6 seconds otherwise I wouldn't like to be on a plane relying on WAAS if it only got an irregular position every so often. One issue is here that very few handhelds actually have the capability to implement WAAS "totally". Cheers, Kerry.

That's ok. "The Stationary ground units used in the WAAS" are not part of the Global Positioning System but a WADGPS (Wide Area Differential Global Positioning System) augmentation system and as such is provided and run by a third party who totally rely on GPS itself, GPS doesn't rely on WAAS. WAAS is also by no means "Global", actually far from it. The only time the DoD would get interested in WAAS (and not directly from the control segment either) is if WAAS had to be put into emergency military mode, in other words shutdown. Cheers, Kerry.

Sept 2001 has no bearing on GPS accuracy, but it appears many thought and still thing so. Cheers, Kerry.

"S" for System, I'll go along with that. The System comprises the Space segment (the satellites), the control segment (the people who control it) and the User segment (that's all the users with their trusty GPS receivers ) Cheers, Kerry.

For a start your comparing seconds and decimal minutes, so things certainly should appear a long way off. 56 seconds = 0.93 minutes so apart from using different formats your really where your supposed to be Just need to work in the one common format. Datum that could be another issue but not really related to format. Cheers, Kerry.

Kerry, Sorry if my comment was unclear. It can be challenging to properly convey sarcasm in text. Cobras GPS is an 18 channel. With 24 active sats, evenly distributed around the globe, using all 18 channels seems like a stretch. Thanks for the info though. I have to assume you work in a technical field of some sort. yeah am aware of the 18 channel receivers and for sure it would be a stretch, gee even 12 can be a stretch even for some of the time. Actually for a fleeting glimse there might be times with 13 (even 14) in view but that would certainly no be from the standard 24 satellite constellation and one certainly wouldn't want to blink. On some days at the north pole one "might" pull 15 satellites in view (at a pinch). Now if some of those channels actually could use Glonass then that would make 18 channels sound reasonable (there are 24 channel receivers available that specifically do this), but somehow I can't imagine the Cobra would/could do that. Cheers, Kerry.