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Turning WAAS off


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Speaking of WAAS...

 

Let's say you have poor WAAS reception. I've seen some people say that in this case your accuracy will be worse than if you had just turned WAAS reception off.

 

I can see how using WAAS might slow down your unit, but could it actually degrade your position accuracy under poor condtions?

 

George

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Rumors say that Garmin's receivers favor corrected sats, if there are enough of them. Say that it does have four sats with 'D' symbols, but all of these are in the same direction on the sky above you. Using only these, may result in such a bad DOP value, that the accuracy will be inferior, in spite of each satellite being more accurate, compared to using all available satellites on the sky.

 

Anders

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I'm generally unable to get a WAAS lock, but recently on a hike I knew I was going to be in a position to get one. So I brought both my Legend and Vista with me to see if WAAS was what all the hype people say it is.

 

I got up there and had a lock on 8 sats on each unit. Both units displayed an accuracy of 12 feet. I kicked on WAAS and waited for the lock. Once I got it the displayed accuracy jumped to 16 feet on each unit and would not budge below that no mater what I tried (holding the unit up higher, aiming it in different direction, doing a little dance for the sat gods).

 

It was a rather big let down. Even if the displayed accuracy is wrong and WAAS did in fact improve my location accuracy, I saw nothing to indicate that that was the case. Given that and the fact the it supposedly uses more battery juice, I'm keeping it off from now on.

 

On the same note... it occurs to me that WAAS was supposed to be for aviators so they didn't smack the ground when they thought they were still at 300ft. Maybe it only improved my elevation accuracy. I didn't check that, nor did I have a known point to check it against.

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quote:
Originally posted by nincehelser:

Speaking of WAAS...

 

.... but could it actually degrade your position accuracy under poor condtions?


 

One could call this situation "poor conditions" as in this case using WAAS outside the ground stations (like Australia) will certainly degrade the position.

 

Just because one has a "WAAS signal" doesn't mean one is receiving valid (or any) "WAAS corrections"

 

Cheers, Kerry.

 

I never get lost icon_smile.gif everybody keeps telling me where to go icon_wink.gif

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Everybody keeps quoting accuracy but what type of accuracy as say 3 metres certainly isn't 100% of the time. Is that 95% or RMS or the manufacturer preferred CEP, which of course sounds better but it ain't.

 

If 3 receivers quoted accuarcy figures of say 3m CEP, 5m RMS, 8m@95%, which one is the better, None in accuracy terms all a equal.

 

It's not simply the number of metres/feet etc but what type of metres/feet they are that counts.

 

Cheers, Kerry.

 

I never get lost icon_smile.gif everybody keeps telling me where to go icon_wink.gif

 

[This message was edited by Kerry on May 07, 2003 at 08:24 PM.]

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