WAAS - Wide Area Augmentation System
Update - May 2008
Still no useful WAAS in Australia so the info below is still valid.
Update - December 2005
From Arthur King,
I spent the last 2 days searching for info on WAAS in Aus!
Update - 23-Oct-2002
How to turn off WAAS on Magellan GPS units
Update - 22-Oct-2002
The role of differential corrections is only part of the reason for WAAS. Its main role is integrity monitoring in that it continuously monitors individual GPS satellites and if there is any abnormality it will not include them in the differential correction. The Jappanese Multifuntion Satellite will hopefully be re launched soon and this will have a footprint covering all Australia. The original was lost on launch about 2 years ago.
As well as supplying weather maps it will also act as a WAAS satellite. The GPS base stations are already in existence and have been there for 15 years as the National Fudicial Network and it is owned by the Commonwealth via Auslig. They would probably require upgrading to output RTCM??? but the network along with the telecommunications network and control centre is there and it is not utilised anything near capacity.
The WAAS system is for category 2 instrument approaches and it is going to be very interesting when international airlines arrive in Australia and discover that this facility no available. Differential corrections with selective availability switched off have about 15 minutes redundancy. The only thing that changes is atmospheric and ionespheric errors and they are stable for up to 15 minutes.
WAAS is a a very good system and the lack of vision by the present government
to not involve Australia in it, will in time prove to be of great national
Here are some observations from GPSOZ's location. They are 4 samples taken over 12 hours each. Two receivers, Garmin GPSmap76 and a Magellan Meridian GPS, with and without WAAS enabled. Basically when using a WAAS capable GPS in Australia, turn OFF WAAS.
In all cases, the averaging feature of both GPS units reported our location as indicated by the blue + in the centre of the screen.
A couple of people have asked me what WAAS is all about. Briefly, its a set of ground stations that send correction signals to a set of WAAS satellites. These in turn broadcast back to your GPS. If your GPS is capable of receiving these correction signals, your accuracy will improve(?) to around 3m
It was originally designed when accuracy was typically +/- 100m ie when SA was switched on. However the information that I have received to date, indicates that there are no ground stations in Australia and NO plans to build any. Hence WAAS correction information is NOT available in Australia and very unlikely to be.
Interestingly Air Service Australia has just conducted a series of tests and found that the average accuracy in Canberra was 2.2m. Given that WAAS accuracy is typically 3m then why do it? Good question.
There is also a couple of technical reasons why WAAS in its current form will never be implemented in Australia:
So the bottom line, discount WAAS in your GPS selection process if your sole use is outside the USA. It's a feature that can't be used in Australia.
More when it comes to hand.