WAAS in AUS?

GIN51E · Post by **GIN51E** » 30 August 05 9:55 pm

Biggles Bear wrote:Interesting. Although I'm still not quite sure I understand, why having changed no settings on my GPS, it is suddenly starting to show that it is using/picking up WAAS information.

thats what i've been asking yet no one seems to be able to answer that.

i've sent emails all over the place to the USA ect and government agency's yet no responses.

riblit · Post by **riblit** » 30 August 05 10:29 pm

GIN51E wrote:
Biggles Bear wrote:Interesting. Although I'm still not quite sure I understand, why having changed no settings on my GPS, it is suddenly starting to show that it is using/picking up WAAS information.
thats what i've been asking yet no one seems to be able to answer that.

i've sent emails all over the place to the USA ect and government agency's yet no responses.

I'm beginning to believe that you (and others) don't have a real understanding of what a differential GPS is and how the system works. The fact that you are receiving a signal does not mean the data are valid for this region. <a href="http://www.trimble.com/gps/whydgps.html">Trimble</a> have a flash presentation that shows how how a differential GPS works and how this evolved into WAAS. 
The tutorial begins <a href="http://www.trimble.com/gps/why.html">here</a> if you want to watch the lot.

Pay particular attention to the distances around the reference stations as that will explain why WAAS does not work in Australia.

Kerry · Post by **Kerry** » 30 August 05 10:56 pm

What we need to solve this issue is for someone to actually come with the Wide Area satellite # that appears to be triggering this apparent sudden "WAAS" indication. My guess is it's not WAAS at all as most manufacturers have plugged the coverage issue these days.

Doesn't change the principle it's still an erroneous signal in Australia and should be ignored, in other words turn the "WAAS" function off.

We were only meters from our Lookout fischer cache (1100 mtrs alt) when this happend. Only briefly though!!

That could be the hint to what's going on here?

More notice of exactly what the satellite number is?

Cheers, Kerry.

ian-and-penny · Post by **ian-and-penny** » 30 August 05 11:26 pm

My 20c

I have had WAAS turned off on my Magellan Yellow since the day I bought it.

Yet I still had a WAAS indication on my GPS last sunday.

Ian

Hounddog · Post by **Hounddog** » 31 August 05 1:18 am

Like I said earlier. You are picking up a signal on the WAAS channel because that's what the GPS is supposed to do. It is where POR is transmitting right above us. But the signal is encrypted and in Australia there is no key for the GPS to understand it.
If your GPS has WAAS disbabled it will still pick up the signal but will simply ignore it.
If your GPS is WAAS enabled it will keep trying to understand that signal and continually waste time trying to factor it into calculations. So turn it Off.

Biggles Bear · Post by **Biggles Bear** » 31 August 05 3:17 am

This is a pretty good site too

Magellan use of WAAS

Magellan uses WAAS in a similar way to the description of Garmin use given above. However they do not have a menu item to turn WAAS on or off. There is a secret menu entry that can do this. Turning off WAAS frees up some channels for regular satellite use and should certainly be performed if you are outside a WADGPS coverage area. As already mentioned Magellan does not display the WAAS satellites on the satellite status screen so there is no indication on the unit whether WAAS is turned on or off unless you are actually receiving WAAS signals. When you are receiving WAAS the epe indication changes to show WAAS and when averaging a position the WAAS indication is present. Note that the unit will continue to use WAAS corrections long after the signal is lost. Some report that corrections will be used for 50 minutes or longer as indicated by the WAAS averging indication. (It is not clear from the report that WAAS data is still being used or it is just a software bug.) If you power the unit down and back up the use of this stale data will be discontinued

So we are recieving signal from POR; I'm guessing that baby didn't go up over the weekend.

So here's the question yet again; Why are we suddenly seeing WAAS on our GPS units? What is it that has recently changed?

acts2youthgroup · Post by **acts2youthgroup** » 31 August 05 9:01 am

Biggles Bear wrote:This is a pretty good site too

Magellan use of WAAS

Magellan uses WAAS in a similar way to the description of Garmin use given above. However they do not have a menu item to turn WAAS on or off. There is a secret menu entry that can do this.

So how do we access this secret menu?

riblit · Post by **riblit** » 31 August 05 10:13 am

acts2youthgroup wrote:
Biggles Bear wrote:This is a pretty good site too

Magellan use of WAAS

Magellan uses WAAS in a similar way to the description of Garmin use given above. However they do not have a menu item to turn WAAS on or off. There is a secret menu entry that can do this.


So how do we access this secret menu?
Following the link to the GPSOZ site I posted earlier in this thread you will find:

To turn off WAAS on Magellan receivers try the following:

From any screen press MENU

Press right arrow, left arrow, right arrow, left arrow in sequence (you may have to do this a couple of times)

A box with 00 in it appears. Use the up arrow key to change the "00" to a "03" and then press ENTER.

A few boxes should pop up. Press ENTER to turn a "ON" to an "OFF" (all boxes will change simultaneously).

Press ESC twice.

Turn off the unit. Then, when you turn it back on the WAAS satellites should not be visible in the satellite screen (W's). Note that the boot screen will still say "WAAS."

Bear in mind that this info could be a couple of years old (see the dates on the page). If that doesn't work you could always email Brian.

Kerry · Post by **Kerry** » 31 August 05 10:13 am

Biggles Bear wrote: ....So here's the question yet again; Why are we suddenly seeing WAAS on our GPS units? What is it that has recently changed?

And my comment again My guess is it's not WAAS at all as most manufacturers have plugged the coverage issue these days. and until someone actually comes up with an actual satellite # to confirm or deny then it's my best guess but here's the scenario.

WAAS is a brand name, the generic name for this type of system is WADGPS. Now as all WADGPS are compatible and work identical I'm not sure if receivers at a recreational level are intelligent enough (at this point) to know which brand name WADGPS they think they are listening to.

ESTB (Egnos) was supposedly to start initial broadcast operations from around July 2005 so the system could be operational stable by the planned 2006 availability declaration. Still being a test signal I would doubt many recreational receivers would currently have the capability (brains) to know the diffence between WAAS and EGNOS as up until this time there has only ever been the one WADGPS. WAAS and EGNOS might be indentical but service quite a different area and in any case the same principle applies, it still won't be of any benefit in Australia.

When there are 2 separate signal sources to confuse people then one could imagine that if this signal is in fact coming from EGNOS IOR-W (which can be seen from Aus) manufacturers will do the same trick as with WAAS, not allow it outside the correction footprint.

Biggles does that outline your question?

Cheers, Kerry.

GammaPiSigma · Post by **GammaPiSigma** » 31 August 05 10:26 am

I turned WAAS off on my meridian ages ago and it boomerangs just as effectively as it ever did.

Mike.

riblit · Post by **riblit** » 31 August 05 10:57 am

Hounddog wrote:Like I said earlier. You are picking up a signal on the WAAS channel because that's what the GPS is supposed to do. It is where POR is transmitting right above us. But the signal is encrypted and in Australia there is no key for the GPS to understand it.
If your GPS has WAAS disbabled it will still pick up the signal but will simply ignore it.
If your GPS is WAAS enabled it will keep trying to understand that signal and continually waste time trying to factor it into calculations. So turn it Off.

Hounddog, would you point me to a reference on the data stream being encrypted. That's something that hasn't come up in my reading and, given the nature of the data, seems rather pointless.

Kerry · Post by **Kerry** » 31 August 05 11:55 am

Another "possible" source of this apparent sudden WAAS "type" signal influx is MTSAT-1R, which is sitting around 140E (just north of PNG) but nobody can verify if they have commenced any MSAS signal tests since it was launched in Feb.

However same principle, still useless.

Cheers, Kerry.

Hounddog · Post by **Hounddog** » 31 August 05 12:33 pm

Hounddog · Post by **Hounddog** » 31 August 05 12:44 pm

Hounddog wrote:
riblit wrote:
Hounddog wrote:Like I said earlier. You are picking up a signal on the WAAS channel because that's what the GPS is supposed to do. It is where POR is transmitting right above us. But the signal is encrypted and in Australia there is no key for the GPS to understand it.
If your GPS has WAAS disbabled it will still pick up the signal but will simply ignore it.
If your GPS is WAAS enabled it will keep trying to understand that signal and continually waste time trying to factor it into calculations. So turn it Off.
Hounddog, would you point me to a reference on the data stream being encrypted. That's something that hasn't come up in my reading and, given the nature of the data, seems rather pointless.

Hi Riblit.

Perhaps "Encrypted" was a poor choice or word there, but for the sake of simplicity I used it as a substitute for....."a signal of digital nature that cannot be understood or used by applications other than for what or where they were intended" Put simply the Yanks might as well have encrypted it for us, because without a WAAS ground station they mean zilch.

Truth is......I am not really sure what exactly is being transmitted or in what format. If your were to tune into the frequency with a scanner, would you be able to read any numbers. Perhaps this is where the problem might lie. If POR ot the ground stations are transmitting numbers in the same format as all the other sats in the the system then occasionally you might find that a series of numbers flukes a reading on WAAS capable receivers. Of course they still won't be correct which still means that WAAS needs to be turned off.

Perhaps it's not POR at all causing the anomalies, but a satellite or ground station transmitting on an adjacent or harmonic channel. Now we are really getting into semantics. Maybe there is some sort of trade off to making smaller GPS's that we don't know about, something that afffects Adjacent Channel Rejection or Selectivity. I have often wondered what must be suffering in the manufacturing of smaller and smaller units.

I do have a scanner capable of picking up GPS frequencies but I am not exactly sure which frequency is which.

Hounddog

The Garner Family · Post by **The Garner Family** » 31 August 05 1:01 pm

Hounddog wrote:Case in point......I am not really sure what exactly is being transmitted. If your were to tune into the frequency with a scanner, would you be able to read any numbers.

The signal being sent it a digital signal. While a number of frequencies are transmitted, the one we read on our user grade GPS's are on 1575.42Mhz. The things being sent are:

* The exact time, read off of the satellites atomic clock; 
* A pseudorandom 1,023 bit long piece of data generated incorporating the time of the atomic clock as part of the seed; 
* Orbital information about the current location, state, movement of all the satellites. 

IANAGPSE (I am not a GPS engineer)... I just got this from <a href="http://en.wikipedia.org/wiki/Gps">wikipedia</a>.