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Loosing Waas Lock


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For a science project, my son and I have been comparing WAAS vs non-WAAS readings over time.

 

For the last 3 days, the WAAS unit (a Vista) has held consistant lock...up to about an hour ago...all the little "D"s went away, and the error indicator jumped. The unit has been sitting in the same location and has a very open view to the sky, so line-of-sight shouldn't be a problem.

 

At 2:30PM it was just fine. The 3:30PM reading indicates WAAS was lost.

 

Thoughts on why it has suddenly lost WAAS? I'll check it again in about an hour and see if it comes back.

 

Update: As of 4:30PM, WAAS is back. ????

 

Thanks

George

Edited by nincehelser
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At 2:30PM it was just fine. The 3:30PM reading indicates WAAS was lost.

Thoughts on why it has suddenly lost WAAS? I'll check it again in about an hour and see if it comes back.

Update: As of 4:30PM, WAAS is back. ????

I won't even pretend to be an expert on WAAS and will never try. It's not worth the head ache. But I do know that you can't ALWAYS rely on WAAS. It can be turned off at any time and or since it's not all that new it could be down for maintainance. Also, a ground station that you are transfering from could also be down. There maybe other reasons but those I have read something about.

 

IMHO it's not something to worry about. If you have 4 or 5 good sat signals you will have as pretty much all the accuracy you need. If you have a WAAS so much the better but it's not something you need to go looking for or wish you had. It's there or it's not.

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Another update. At 5:50PM, I still had WAAS lock, but apparently only have the correction data for two sats. It's gone from all "D"s across the board, to no "D"s, to all "D"s, then back down to two "D" over the last few hours.

 

What really bugging me it that it seemed so darned stable Saturday and Sunday, but now it's acting funny. The weather is even better today (perfectly clear skies) than it was this weekend (cloudy and rainy). I can't imagine why WAAS should suddenly go bad on me. (The units are sitting on my patio, and are unmoving)

 

I was looking for that site that tells you about WAAS outages, but it doesn't seem to be there anymore. Anyone know where I can find out about the current condtions of WAAS? Maybe the firmware in my Vista is still buggy, I know I don't have the latest and greatest, but it isn't ancient.

 

It's not that I'm really worried about it. It's just the main point of my son's science experiment to see if WAAS really lives up to its expectations for consumer gear.

 

George

Edited by nincehelser
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Aren't there ONLY 2 WAAS satellites? Does the unit show you receiving WAAS from more than 2?

A good thing to check. I think #35 is the one I usually notice, and when the readings went goofy, its signal seemed to be marginal.

 

I think the other one is #47? I haven't been really checking on it. I assumed being in central Texas, and being able to easily see the whole southern sky from east to west, that picking up either one shouldn't be a problem.

 

In my last check WAAS was strong again. I'll be checking again in 20 minutes or so.

 

George

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nincehelser - post your question on newsgroup sci.geo.satellite-nav

 

sam wormley frequents that site and will undoubtedly have some insight for you on your waas concerns. he can also give you some sites that would have near realtime waas info.

Edited by Vlad
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Just checked the sat #'s. I'm getting #35, but I'm not seeing #47 (assuming that's the right number). I'm looking at the sat footprints, and I guess seeing #47 isn't likely from central texas. It looks like the only parts of the US that can see both sats are the west cost.

 

Well...there's another assumption blown to bits.

 

George

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N 30 29.863

W 97 43.941

 

Actually, that's a couple block away, but should be close enough. I've actually haven't converted the location into DD MM.MMM for my house.

 

UTM of my patio, though, would be

 

14R E 621846 N 3364370. (I'm getting real familiar with those numbers. I chose UTM to make the math easier.)

 

Thanks

George

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Aren't there ONLY 2 WAAS satellites? Does the unit show you receiving WAAS from more than 2?

Yes there are two sat sending the data, but they sends the data for all other sats. The "D"s on a Garmin indicate for what sats the correction information had been received.

 

I can certainly see the WAAS getting dicey if anything messed with reception of that one sat, but I don't know why it happened. Local signal interference?

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