Waas

[tmmorris]

Simple, really...

Does WAAS work at all in the UK? Have e.g. the USAF installed any transmitters for their own use?

I'm sure I saw my GPS indicate that it was receiving WAAS the other day...

Tim

[Fuji Abound]

WAAS is turned on most of the time BUT there are no ground stations in place in Europe so the enhanced accuracy does not follow.

[High Wing Drifter]

There is a project in Germany looking at implementing fake ground based satelites (pseudolites) to provide RAIM precision approach coverage.

I'm not really clear on this, but I think this is different in that WAAS corrects the satelite signal, whereas a pseudolite is to all practical effects a satelite and completely independant of all other satelites.

[tmmorris]

WAAS corrects the satelite signal

Yes, that's how I understand it. The WAAS station knows its own location and the location the GPS satellites tell it that it's in; it works out the difference and broadcasts that. My GPS actually calls it DGPS (Differential GPS) which appears to be another name for the same thing.

Tim

[IO540]

I thought the whole idea behind Galileo was that GPS approaches will become authorised once this is up and running, and the condition will be a receiver capable of receiving a paid-for signal.

If they bring in WAAS in Europe, what's the point of Galileo?

What about EGNOS?

[slim_slag]

Differential GPS gives a headline accuracy of around 10m, WAAS around 3m and good enough vertical accuracy to replace an ILS.

What about EGNOS? Well, it's still dependent on a non European infrastructure, and for various reasons the Europeans want their own GPS which will essentially duplicate the American version in every way except cost to the consumer.

[tmmorris]

I thought the one that provided vertical guidance was LAAS? (local)

Tim

[slim_slag]

Yes, LAAS will provide Cat II and III, but WAAS should provide Cat I, which is way good enough for the likes of me :)

[tmmorris]

I'm truly depressed about Galileo. I naively saw it as a way to get GPS approaches here; I hadn't considered the charging aspect. The whole thing seems pointless and cynical to me: much better to spend the money on WAAS/LAAS for UK airfields.

Tim

[S-Works]

WAAS and DGPS are different technology with the same application. DGPS beacons were mostly coastal or "Special use" and were a tower that broadcast a position correction based on a surveyed position. This waws than transmitted and GPS recievers with a special DGPS antenna would collect both signals and apply the correction.

A lot of units were DGPS capable but all required the extra antenna. No handlheld unit that I have ever seen actually had the antenna. The DGPS antenna on my boats was quite large.

When the USA switche off SA the DGPS beacons were also switched off.

WAAS uses a pair of satelites over the continental USA to broadcast a time correction signal. The unit then uses the corrected time to amend the almanac that it downloads on startup and thus correct the standard GPS signal.

A DGPS signal is more accuracte if you were going to supplement the signal for a precision approach as it can also fix height data as well due to a known position.

[slim_slag]

I don't think the US Coastguard turned off the DGPS system when SA was turned off, see IGPS FAQ (http://pnt.gov/sa/faq.shtml) I understand that DGPS in practice will provide 3m accuracy near the station, reducing by 1m every 100 miles, but the headline figure is still 10m.

EGNOS is the same as WAAS, so Europeans have in theory Cat I approach ability using the US system, but apparently don't want to use it in aviation. I share the cynicism about European use of GPS in aviation, it reminds me of mobile phone use on planes. The authorities banned it on spurious safety grounds until somebody worked out how to make money from it, and now it seems OK!

[bar shaker]

It is almost certain that Galileo will not now happen.

The project needs another £400m which was expected to come from industry. Companies have refused to invest in it unless it has military applications, Galileo cannot have military applications unless the European Constitution is ratified allowing the EU to establish a defence force of its own.

With the EU in bed with China, the US threatening to jam the signal if China is a partner, and Germany and France fighting over who will control it, I think we can safely say that the lack of Constition is more of a blessing than we could have hoped for.

[IO540]

I read somewhere that some of the Galileo satellites were ready for launch...

As for the business model, anybody can see it's nonsense. The American GPS system is free and is more than accurate enough for just about any vehicle/ship/aircraft en route navigation requirement. As I go around a roundabout, TomTom3 tells me which bit of the roundabout I am on and where to turn off.

Commercial aviation uses mostly ILS and occassionally VOR or NDB based approaches so they don't need GPS approaches. In Europe, there may be a market on the fringes (e.g. Ryanair flying into some regional airport that doesn't have an NDB or VOR) but that's all it is.

Ultimately, that's why we have no GPS approaches in the UK. The airlines use ILS etc, small-field commercial ops can get special CAA permission for a private IAP based on some nearby navaid, and the bit of GA that would use GPS approaches is too small to make it worth while for an airfield to spend the money getting one approved.

There is sure to be a big market for GPS approaches in the emerging economies (e.g. I bet China is going to build a load of airports) but they will have no incentive to pay the Europeans when the American system is free.

The only way to make Galileo pay is to somehow force a whole load of present users of navigation systems to use it. For example, closing down instrument approaches and forcing the users to use Galileo instead. But a crazy plan like that could never be pulled off in international aviation.

Maybe I am missing something?

[tmmorris]

the bit of GA that would use GPS approaches is too small to make it worth while for an airfield to spend the money getting one approved.

and are probably already using non-approved DIY approaches based on GPS anyway, as it's perfectly legal...

until it's banned, anyway.

Tim

[IO540]

and are probably already using non-approved DIY approaches based on GPS anyway, as it's perfectly legal...until it's banned, anyway

I don't think that a whole lot of pilots are doing DIY letdowns, using GPS alone, to the sort of levels possible with ILS i.e. 200-300ft DH.

And if you do a letdown to 1000ft AGL (which is only slightly above some NDB approaches) you are still legally at the MSA. Even the FAA allows IFR flight AT the MOCA.

It's the area between the two levels. Is there any statistically valid evidence of problems there?

The bottom line is that it can't be enforced, because nobody can tell when the pilot got visual. Except possibly at a towered field which has a cloudbase measuring device, and even then only in pretty extreme cases.

[High Wing Drifter]

I read somewhere that some of the Galileo satellites were ready for launch...
In addition I read that GALILEO was meant to integrate NAVSTAR and GLONASS. This would lead to, I think, 80 satellites for civil use!!
There is sure to be a big market for GPS approaches in the emerging economies (e.g. I bet China is going to build a load of airports) but they will have no incentive to pay the Europeans when the American system is free.
Pound to a penny China uses GLONASS. I'm assuming that the Russian system is fit for purpose and that the reason why we are not using it is mostly political. When compared to NAVSTAR (US GPS), GLONASS provides much better coverage at higher latitudes.

[skydriller]

The only way to make Galileo pay is to somehow force a whole load of present users of navigation systems to use it. For example, closing down instrument approaches and forcing the users to use Galileo instead. But a crazy plan like that could never be pulled off in international aviation.

Errr.......Irony, right? Like steely, but harder? Want to take a bet on that not happening? I think that is exactly what is going to happen.....

I dont think Im crazy, just very, very, cynical...:suspect: ...

Regards, SD..

[IO540]

HWD

We must both be reading stuff on the internet ;)

I read that Galileo was finally agreed to be compatible with Navstar, to enable use of the same chipsets, etc.

Skydriller

I wasn't being ironic, for a change. I don't really think that Europe (which, when you look at a globe, is a really really tiny part of the earth, despite owning most of the earth 400 years ago) would be able to force all the world's airlines to equip their airliners with "Galileo approved" GPS receivers, containing pre-paid decryption devices (like Sky TV - how else can anybody charge for GPS reception?), change their operating procedures, force crew retraining, etc. just so they can fly to that tiny place called European "Union". It would be a complete joke.

Perhaps somebody here has got their head into the Galileo proposals on how to get money out of it, and is able to comment. I can't see it.

There are lots of very good technical reasons for GPS approaches over ILS etc, e.g. 2D- and 3D-curved approaches become possible, but it can all be done with Navstar, for free.

[High Wing Drifter]

We must both be reading stuff on the internet
Indeed! A good set of Google goggles see along way :) Although, another plug for the ATPLs, they cover quite a lot detail on technological and operational aspects of GPS.

[M609]

The first SCAT-1 system has been installed in Norway, and is in operational use at ENBN/Brønnøysund.
In the next 4 years 24 other STOL regional airports will get the system. Noen of these airports have precision approaches today due to terrain/cost issues. (Offset approaches and no flat ground to install a GP without astronomical costs)

(SCAT-1: Special category 1, a bargain version LAAS)

[Shaggy Sheep Driver]

Commercial aviation uses mostly ILS and occassionally VOR or NDB based approaches so they don't need GPS approaches. In Europe, there may be a market on the fringes (e.g. Ryanair flying into some regional airport that doesn't have an NDB or VOR) but that's all it is.

The driver for commercial aviation to use GPS is the money they'd save in no longer having to maintain those ILS and beacon systems.

SSD

[slim_slag]

Free flight should also save the airlines a ton of money. I read a single LAAS installation will cover all runways within 20 miles and cost less that a single ILS. I guess all they have to do now is to make it work.....

M609, how have they got around the integrity problems?

[IO540]

The driver for commercial aviation to use GPS is the money they'd save in no longer having to maintain those ILS and beacon systems.

There are two distinct lots of people who are in this: the airlines, and the "national air traffic services" who maintain the ground stuff.

The airlines have to have all the kit anyway; unless you dedicate a plane to a single intra-EU route all its life. The last thing they would want to do is "pay as you go" extra for a GPS approach.

The incentive for GPS approaches would be in the navaid maintenance group. But they would still need to force all airliners to equip the planes and retrain the crews. We aren't talking of US-style GPS approaches; these are GPS guided precision approaches down to 200ft or less, down to Cat3c. This would take not years but decades.

If Galileo was meant to be a play on this, it would be a very long shot. Also Navstar isn't going to stand still all those years; it will get better, more powerful (better S/N ratio).

If savings are obtained by decommissioning navaids and landing systems, would those savings be passed on to airlines in reduced en-route charges? I think the answer is obvious :O

I bet the direct cost of maintaining say the ILS at Heathrow is an insignificant part of the money which an airliner pays to land there and unload its contents.

[M609]

M609, how have they got around the integrity problems?

Not sure what you are reffering to, but as far as I know, it works well.

Still just one airline that have right boxes in the planes tough, Wideroe Airlines. (They have been a part of the project since day one, they are by far the biggest player on the STOL network)