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WAAS in Australia

Old 15th Nov 2012, 23:16
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WAAS in Australia

With the next federal election in the foreseeable timeframe, is it time for industry and all other interested groups to start to very actively lobby for an Australian program to install ground stations to utilise Japanese MSAS/MTSAT satellites?
This could presumably partly utilise the ADS-B infrastructure and thus it would be cheaper than a de-novo system.
Surely now is the time for interested parties to join together, get the media involved, and lobby the politicians for support in the lead up to the election (when politicians and parties are more amenable to lobbying).

John
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Old 15th Nov 2012, 23:30
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That would be much too simple. We will instead design our own system because the other one wasn't invented here.

...and when that doesn't work after spending billions, we will eventually buy WAAS.
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Old 16th Nov 2012, 03:02
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and when that doesn't work after spending billions
Billions on what, Sunfish?
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Old 16th Nov 2012, 05:28
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Our very own 25 or more ground stationsto give us Geo reference for the GPS signal
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Old 16th Nov 2012, 08:23
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With the next federal election in the foreseeable timeframe, is it time for industry and all other interested groups to start to very actively lobby for an Australian program to install ground stations to utilise Japanese MSAS/MTSAT satellites?
This could presumably partly utilise the ADS-B infrastructure and thus it would be cheaper than a de-novo system.
While I would very much like to see this happen, I think it's very unlikely.

The SBAS review in 2011 came to a clear conclusion that was something like "difficult to justify the costs" of around $150 - $200 million, and that's assuming we do the intelligent thing and piggyback on MSAS. There was already a fair bit of lobbying going on during the SBAS review. I don't see how more lobbying will change minds.

In the longer term, there is hope for an SBAS in Australia, though. There are a bunch of new satellite constellations running on multiple frequencies that are coming online (slowly) - namely GPS block III, galileo, glonass, compass and qzss. Supposedly, by using the multi-frequency + multi constellations, we can get the fault tolerance and accuracy benefits of SBAS without the need for a ground reference network (or possibly with a much smaller ground reference network). Unfortunately, this is still at the research stage, and it'd probably be 2020 or later before it will be in a useable form.

- S
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Old 16th Nov 2012, 08:56
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Technically I think this is not possible. From what I understand the WAAS transmissions made in Japan are referenced to GPS receivers (measuring the differential) on the ground in Japan providing the WAAS capability over that local geographic area.

I would think that potentially using that WAAS differential signal in Australia (which is essentially a time shift of the GPS signal in the receiver) could put an aircraft way off course compared to turning the WAAS signal off. GPS receivers work their positions out by looking at the time differance between GPS signals, WAAS makes an adjustment to these time series.

A receiver in Australia would see a different satellite constellation than a receiver in Japan would at any given time (a satellite that is visible in Japan could be beyond the horizon in Australia), and is the WAAS transmission is making corrections to only part of the constellation that a receiver in Australia would have visible.
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Old 16th Nov 2012, 10:56
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Not quite right regarding the MTSAT.

The Japanese Department of Transport wanted to get Australia on board from the start. So much so that there is a ref station uplink in Canberra as well as one in Hawaii. All that is required is the ground constellation to work out the differentials and transmit the code up to the MTSAT. There is already a transponder pointing this way. If you are wondering what coverage would be like, just look at any satellite picture of our neck of the woods. Those pics are from the MTSAT. $300million is bogus, the ground stations are already there, surveyed in, already talking to mummy, just need another aerial and another tray in the rack.

What IS required is to organise a cohort of like minded industry users to lobby Canberra to show it isn't just aviation that can benefit from this technology. Lord knows it will save lives out in the GAFA...GAFA? any time there is marginal wx it will save lives or rather, put lives at less risk.
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Old 17th Nov 2012, 00:56
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Folks,
One of the obstacles we face is that aviation is only one small section of the community that uses GPS systems.
In the US in particular, there are many ground based users of GPS/WAAS positioning accuracy.

With the coming of the new generation of GPS, WAAS like accuracies will be available without WAAS, but only to slow moving targets.

Thus, we are faced with a situation where aviation will be the only beneficiary of WAAS, the notional cost can only be spread over a very narrow field, in any cost/benefit analysis.

Of course, in a "user pays" environment, WAAS is unpopular, because gummint/AirServices haven't been able to devise a way for charging for it.

Tootle pip!!
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Old 17th Nov 2012, 00:59
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Technically I think this is not possible. From what I understand the WAAS transmissions made in Japan are referenced to GPS receivers (measuring the differential) on the ground in Japan providing the WAAS capability over that local geographic area.
It's possible. MSAS (and the other WAAS compatible systems) are designed to provide service over a wide area (theoretically, the entire earth, but this may be limited by the available bandwidth in the SBAS bitstream). The correction messages fall into two categories - the satellite clock/position errors, which are obviously useable whether the end user is in Japan or in Australia; and the ionosphere corrections. We can extend MSAS to provide the ionospheric corrections over Australia if we add a ground reference stations to the MSAS reference network. It's this local ground reference network that we'll need to get funding for.

Actually, an alternative setup would be to build our own SBAS system, and simply use the MSAS satellites to broadcast the correction messages. However, I don't see any practical advantage in this approach over the extend-MSAS approach.

the ground stations are already there, surveyed in, already talking to mummy, just need another aerial and another tray in the rack
Errrm... We need a full network of ground reference stations - a single station won't give sufficient coverage to get the necessary ionospheric correction data.

- S
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Old 17th Nov 2012, 01:54
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The correction messages fall into two categories - the satellite clock/position errors, which are obviously useable whether the end user is in Japan or in Australia; and the ionosphere corrections. We can extend MSAS to provide the ionospheric corrections over Australia if we add a ground reference stations to the MSAS reference network.
I understand how the corrections are made and what they are correcting, my point was without the ground stations in Australia, that see the satellites that a receiver in Australia would see, a WAAS correction from Japan would not be technically possible.

However, I don't see any practical advantage in this approach over the extend-MSAS approach.
We should leverage on equipment available elsewhere to reduce costs, it would be pointless having a system which requires Australia specific avionics.
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Old 17th Nov 2012, 03:29
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Errrm... We need a full network of ground reference stations
That's what he's saying, we have a network: the ADS-B ground stations. Just a bit of extra kit in them and done.
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Old 17th Nov 2012, 04:22
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Lordy-lordy,

As Leadsled says (we are on the same page brutha) the ONLY reason it aint happening is because the turds in Canberra haven't figured out a way of charging for it. Good ole Australian user pays! If a politicians wife, son or daughter (or mistress, gay lover etc) is killed through it not being switched on, rest assured it will be switched on the day after.
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Old 17th Nov 2012, 10:11
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Found out today, you can actually polish a turd if you soak it in liquid nitrogen first, weshould tell the folk in Northborne Avenue.
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Old 17th Nov 2012, 11:32
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As Leadsled says (we are on the same page brutha) the ONLY reason it aint happening is because the turds in Canberra haven't figured out a way of charging for it. Good ole Australian user pays! If a politicians wife, son or daughter (or mistress, gay lover etc) is killed through it not being switched on, rest assured it will be switched on the day after.
There is already a government funded network in place, however I do not think it is aviation grade. Geoscience Australia is the federal government organisation responsible for managing the Australian geospatial infrastructure. The network is already used for marine, land, and airborne applications.
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Old 17th Nov 2012, 21:16
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I kind of agree with Lead Sled / Jack Ranga, but think the stumbling block to WAAS is that the airlines don't need it. The hockey stick high traffic routes are served by ILS and no where else really matters.

Although (with less sarcasm) most other locations in Australia have good enough weather than GNSS NPA is good enough.

It should be noted that Australia does have WAAS beacons, but they point to sea for marine use and are not usable for aviation.
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Old 17th Nov 2012, 21:32
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I do not think it is aviation grade
You mean over-priced, under performing and without validation or redundancy?

Australia does have WAAS beacons, but they point to sea for marine use
I don't think that is WAAS, but rather a completely separate system and you need a special receiver, just a normal WAAS one won't do. Farmers use a GBAS too for auto-steering their tractors, but again: not WAAS.
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Old 18th Nov 2012, 05:02
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One of the major benefits of SBAS is the improved availability of the GPS signal, so an alternate is not required when your destination is only served by a GNSS approach. I would have thought that this is more important (cost-saving) to Australian pilots than the use of lower approach minima, given our weather conditions most of the time. It will be even more important when Airservices gets around to de-commissioning many of the local NDBs.

But this is likely to be addressed by receivers simultaneously using Galileo and GPS Block III signals within the next ten years. (More satellites to choose from, and receiving on two or three frequencies simultaneously.) So as a tax payer I'd question the wisdom of developing a network of SBAS reference stations at this stage.
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Old 18th Nov 2012, 05:25
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WAAS is a form of differential GPS (DGPS), nothing more, nothing less. It improves accuracy by a) proving an accurate ground based position, b) improving error checking of other satellites and c) importantly for instrument approaches, it allows triangulation from a low reference to give better vertical location. Trying to triangulate from overhead satellites results in triangles with very acute angles which has poor precision. You can have as many satellites as you want does not improve vertical accuracy. You can already buy handheld GPS units that will receive GPS, GLONASS and Galileo satellites. I think that gives access to maybe more than 60 satellites. How many do you need?

Without knowing the costs, I don't believe WAAS stations would be expensive. The money would be in the building, antennae, UPS, etc. The technology of the WAAS transmitter is cheap. It will, however, require ASA to create a bunch of new certified approaches. Maybe that is the real stumbling block?
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Old 18th Nov 2012, 05:43
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Is it not correct that only one or two ground stations are required for the Australian continent for WAAS? If that is the case, there is NO excuse for it not being available.
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Old 18th Nov 2012, 05:52
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Surely with the savings in maintenance requirements on the NDB's and VOR's that are shut down (or will be shut down in the near future) the cost of this new technology would be covered.
GPS/RNAV is all we will have to play with in crook weather west of the sandstone curtain so there would be a significant safety aspect to consider. Any vertical guidance to possible lower minimums would be a real plus. Alternate requirements, while most important, are a real pain when there is a need to carry heaps of fuel because of the distance to the nearest alt.
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