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What is WAAS and should I enable it?


Stumpy434
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Back in my GPS V days, the manual warned that turning on WAAS would slow system performance and negatively affect battery life. Is that no longer true with the latest units? I'm running an eTrex Legend HCx. Thanks.

 

--Bill

On the current generation Garmins, there is no discernible impact on speed or battery life with WAAS on. (Do a search for "battery life" on this forum to see some posts which have measured battery current with WAAS on and off.)

 

Note that it will take a few minutes to get a differential lock, but the speed of getting a 3D fix for a cold or warm start, paging between screens, etc, is unaffected.

 

Hope this helps!

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On the current generation Garmins, there is no discernible impact on speed or battery life with WAAS on. (Do a search for "battery life" on this forum to see some posts which have measured battery current with WAAS on and off.)

 

Note that it will take a few minutes to get a differential lock, but the speed of getting a 3D fix for a cold or warm start, paging between screens, etc, is unaffected.

 

Hope this helps!

Indeed it does! Just makes me wonder why Garmin has it default to off :rolleyes:

 

--Bill

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Indeed it does! Just makes me wonder why Garmin has it [WAAS] default to off :rolleyes:

 

--Bill

There is some question as to whether having WAAS on when you are out of range of WAAS ground-station coverage will actually degrade accuracy. (Note that I am talking about actual positional accuracy, not just the estimate of accuracy that the GPSr reports, which is NOT the same thing!) This was certainly the case on the older units, but I suspect that Garmin may have modified the algorithm so as to disregard ionosphere corrections when you are out of range. (Note - pure supposition - Garmin don't say.)

 

I am based in Australia, and am still experimenting with my Summit HC. So far, having WAAS on (even though I am well outside the base-station coverage) doesn't seem to have adversely affected my accuracy, but I will need a lot more experimentation to be 100% confident this is the case.

 

Accuracy with WAAS off will generally be "very good" (5 metres or so seems to be pretty typical) wherever you are located in the world.

 

If you are in North America (and possibly Europe - don't know quite how Garmins use the EGNOS signals), you should find accuracy is generally somewhat better with WAAS on - say 2 to 3 metres.

 

If you are outside North America / Europe and have WAAS on with an older unit, you can definitely get worse accuracy from time to time (due to application of incorrect ionosphere corrections, I believe).

 

If you are outside North America Europe and have WAAS on with a current generation Garmin unit, you MAY not get any accuracy degradation, but I haven't seen anything yet which would convince me that the accuracy is any better.

 

Hope this helps.

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Greetings all! Another newbie here... just bought an explorist 600 used of course and was wondering how I can check to see if WAAS is enabled (or on). Will I also see a "D" show up in the tracking page? I am not seeing it track anything above 32. I have downloaded and installed the latest firmware as of a couple of days ago. Would appreciate any and all help.

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There is some question as to whether having WAAS on when you are out of range of WAAS ground-station coverage will actually degrade accuracy. (Note that I am talking about actual positional accuracy, not just the estimate of accuracy that the GPSr reports, which is NOT the same thing!) This was certainly the case on the older units, but I suspect that Garmin may have modified the algorithm so as to disregard ionosphere corrections when you are out of range. (Note - pure supposition - Garmin don't say.)

 

A note about "estimate of accuracy that the GPSr reports": On my Legend HCx, the reported accuracy does not take into account WAAS. If I am getting a accuracy estimate of say, 15 feet, without WAAS, then turn it on, it still shows 15 feet... I would expect it to change somewhat. Same thing if I turn it off: no change...

 

--Bill

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A note about "estimate of accuracy that the GPSr reports": On my Legend HCx, the reported accuracy does not take into account WAAS. If I am getting a accuracy estimate of say, 15 feet, without WAAS, then turn it on, it still shows 15 feet... I would expect it to change somewhat. Same thing if I turn it off: no change...

 

--Bill

How long do you give it for the accuracy to change? It will take several minutes to get all the corrections. It may even be showing 'D's when it has the orbit and clock corrections but not the full iono grid yet.

 

One thing that WAAS will do for the accuracy estimate is make the estimate better. In particular, it will have a better idea of how big the ionospheric error may be when otherwise your GPSr basically has to guess. That's why sometimes people see the EPE actually get bigger when they turn on WAAS.

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