WAAS

[+admo1972]

Recently, I've always turned on WAAS hoping that my position would be more accurate. But on closer investigation, I don't think my Vista has ever actually acquired a WAAS sattellite (never seen a bar on sats 33 or higher, the WAAS satellites, if I recall the numbers correctly). I'm guessing that being at roughly 40 degrees latitude, the WAAS geostationary satellites are just too far south for my receiver to get them, unless I sit out on a big lake or a cornfield.

 

Has anyone actuially acquired WAAS satellites from this latitude in wooded areas and such?

[+Dryphter]

On all the time. According to my Garmin manual, having WAAS on and not getting a 'WAAS signal' can degrade accuracy, so the unit automatically chooses the most accurate method. No reason to turn it off.

[+Knight2000]

Recently, I've always turned on WAAS hoping that my position would be more accurate. But on closer investigation, I don't think my Vista has ever actually acquired a WAAS sattellite (never seen a bar on sats 33 or higher, the WAAS satellites, if I recall the numbers correctly). I'm guessing that being at roughly 40 degrees latitude, the WAAS geostationary satellites are just too far south for my receiver to get them, unless I sit out on a big lake or a cornfield.

 

Has anyone actuially acquired WAAS satellites from this latitude in wooded areas and such?

I thought WAAS ground based and not from satellites.

 

I didnt know i could even turn off WAAS on my unit.

[+admo1972]

According to my Garmin manual, having WAAS on and not getting a 'WAAS signal' can degrade accuracy

I don't quite follow (I'll have to recheck my manual to see later). If I read that correctly, it would seem an argument against having it on.

 

No reason to turn it off.

Having WAAS off saver battery life. How much, I don't know.

 

I thought WAAS ground based and not from satellites.

I didnt know i could even turn off WAAS on my unit.

 

WAAS originates from ground stations in North America, but the WAAS signal comes from 2 dedicated satellites in geostationary oribt, one over the Atlantic and one over the Pacific.

 

Most GPSr with WAAS capability have that option turned off by default. So if you didn't know you runit could be turned off, it is probably off now, and you need to go and turn it on.

Edited May 7, 2007 by admo1972

[+Cardinal Red]

I almost always keep it on just so I don't have to mess with the settings when I want WAAS (using GPS Map 76CS). Quite often I can get WAAS correction in the woods of southeast PA. Of course it usually only matters when you are standing still (while trying to find a cache or mark a hide). I often have to turn in place looking for a WAAS signal. Sometimes I get nothing, but 10 feet away is a usable signal.

 

I usually hook up to external power and an external antenna while driving to a cache site to make sure I have a good WAAS lock before venturing into the woods. But if you let your unit just sit in an open area for half an hour you should get the WAAS lock in NJ.

[+Knight2000]

WAAS originates from ground stations in North America, but the WAAS signal comes from 2 dedicated satellites in geostationary oribt, one over the Atlantic and one over the Pacific.

 

Most GPSr with WAAS capability have that option turned off by default. So if you didn't know you runit could be turned off, it is probably off now, and you need to go and turn it on.

Thanks for that info. I was totally unaware of that.

 

Im certain our WAAS is on. After you have said that i am unsure. The manaul makes no reference to turning it on or off anywhere. I guess i need to look!

Edited May 7, 2007 by knight2000

[+Knight2000]

After searching it seems you have to go to a special hidden menu to turn WAAS off. Why would Magellan do that?

[tossedsalad]

Recently, I've always turned on WAAS hoping that my position would be more accurate. But on closer investigation, I don't think my Vista has ever actually acquired a WAAS sattellite (never seen a bar on sats 33 or higher, the WAAS satellites, if I recall the numbers correctly). I'm guessing that being at roughly 40 degrees latitude, the WAAS geostationary satellites are just too far south for my receiver to get them, unless I sit out on a big lake or a cornfield.

 

Has anyone actuially acquired WAAS satellites from this latitude in wooded areas and such?

I thought WAAS ground based and not from satellites.

 

I didnt know i could even turn off WAAS on my unit.

 

Geostationary satellites are some 22,000 miles above the equator. The radius of the earth is less than 4000 miles. At 40 degrees latitude the satellites will still be 41 degrees above the horizon. I am at 39.4 degrees in Maryland and I have have pretty much no trouble receiving WAAS satellites unless I am behind a hill. In fact, I usually receive *both* WAAS satellites!

 

I don't think you will see a bar for a WAAS satellite. I just got a bluetooth GPS receiver and have been playing with the software to show the data. This has been educational regarding the meaning of the skymap and signal bars. They all coorespond to data that is calculated by the GPS engine and typically reported in NMEA sentences. The GSA command reports the active satellites, meaning used in the GPS calculations. The GSV command reports the location of all viewable satellites relative to the receiver and their signal strength. The displays on the tools I am using show the signal strength bars with heights according to the data reported by the GSV command. The skymap shows the location of each statellite as reported by the GSV. They typically color the bars and the satellite points to indicate which satellites are used in the position calculations as indicated by the GSA command.

 

My merigold would not show a WAAS satellite with a signal strength bar, I assume because that is not reported in either of these commands. It would show them at fixed positions once they were being received. The WAAS satellites also would be colored or not which I assume indicates if they were being used to improve the position accuracy. But the two displays did not always match on the merigold. Some satellites would be colored on one and not the other part of the display. I am not sure why that was and when I asked Megellan about it one time I never got a satisfactory explanation.

 

BTW, WAAS is based on measurements made using accurately located ground stations. An offset between the actual location and the calculated location is determined. This differential information is sent up to the WAAS satellites to be picked up by WAAS capable receivers to improve the accuracy of the calculations.

[TeamCypherX]

If I'm not wrong there are now three WAAS satellites. The entire continental U.S. should now be covered by at least one satellite with the possibility of picking up two or even three. I live in the Upper Peninsula of Michigan and I can pick up all three (although only one at a time) with my 60CSx and two with my Quest. It seems that the Quest's firmware does not recognize the new sat.

 

The newer Garmin models will automatically disable the use of WAAS should no satellites be available but will switch it back on if it locates one of them. I leave it on all the time.

 

That's my two cents.

 

Robert

[+EraSeek]

Recently, I've always turned on WAAS hoping that my position would be more accurate. But on closer investigation, I don't think my Vista has ever actually acquired a WAAS sattellite (never seen a bar on sats 33 or higher, the WAAS satellites, if I recall the numbers correctly). I'm guessing that being at roughly 40 degrees latitude, the WAAS geostationary satellites are just too far south for my receiver to get them, unless I sit out on a big lake or a cornfield.

 

Has anyone actuially acquired WAAS satellites from this latitude in wooded areas and such?

 

They are not too far south. Yes you should see a bar for a WAAS sat. You will see "D's" on the other sat bars if you are getting WAAS corrections. I suspect you have your GPS in "battery saver mode" which will not allow WAAS reception because of the slower update rate. Turn that off. Go to menu> setup> enable WAAS, and find an open area where you havea good sky view and allow about 15 or 20 minutes to load WAAS for the first time. After that you are good to go.

 

Here is current WAAS coverage in near real time: http://www.nstb.tc.faa.gov/vpl.html

 

Here are the WAAS sats poitions and there numbers. There are 4 of them.

Edited May 8, 2007 by EraSeek

[+apersson850]

Garmin's receivers will show the signal bar for WAAS/Egnos satellites as well, provided they do show any signal bars at all. Some of them will even tell you if it has computed a differential 2D/3D position. If they do that or not depends upon the model.

 

In reasonably open areas I can receive Egnos, in spite of being at 56° north.

[+Knight2000]

After confusion on my MeriGold i contacted Magellan. They informed me that it is not possible to turn off WAAS. Seems odd since i found other info on how to do it...

[+admo1972]

I suspect you have your GPS in "battery saver mode" which will not allow WAAS reception because of the slower update rate. Turn that off. Go to menu> setup> enable WAAS, and find an open area where you havea good sky view and allow about 15 or 20 minutes to load WAAS for the first time. After that you are good to go.

 

I've never used battery saver mode. It seems the "problem" is that I never gave the GPSr enough time to acquire the WAAS satellite. For the record, I've until yesterday, left WAAS on, no battery saver mode off, and I have never seen any bar on sats 33 and 34, nor have any of the regular sats had the "D" in the bar, indicating that their info has been corrected (the differential and all that, iososphere stuff).

[Dale_Lynn]

Does anybody have any proof that turning off WAAS actually saves battery life. I always assumed it was sort of a urban legend. Seems to me the processor in GPS is running all the time. So WAAS data is just some more data in the data stream and not a separate unique function that uses a area of the chip that needs to be turned OFF/ON... I always though turning WAAS OFF/ON was just a software feature to block or pass a specific series of bits in data stream.

 

Dale

[+GPSlug]

Does anybody have any proof that turning off WAAS actually saves battery life. I always assumed it was sort of a urban legend. Seems to me the processor in GPS is running all the time. So WAAS data is just some more data in the data stream and not a separate unique function that uses a area of the chip that needs to be turned OFF/ON... I always though turning WAAS OFF/ON was just a software feature to block or pass a specific series of bits in data stream.

 

Dale

Tracking the WAAS signal takes more processor time because it's higher rate data with a more intensive encoding scheme. It used to be more significant, but with modern chip design it's not a huge effect.

[Team Marble]

I have a Legend Cx that had software 2.30 that would not look for the 2 new WAAS satellites # 48 & 51. I upgraded to the latest software 2.70 and did a soft reset (hold upper left zoom and then press power). Now I get both WAAS 48 & 51 and get 6 to 9 foot accuracy - SW Michigan. I think WAAS 48 is still not fully functional. BTW, I did the software upgrade to fix the 40 foot too far east problem the Cx seemed to have. Remember the WAAS accuracy is only good if the geocache coord's were established with a WAAS enable GPS.

[DogFleazJR]

Recently, I've always turned on WAAS hoping that my position would be more accurate. But on closer investigation, I don't think my Vista has ever actually acquired a WAAS sattellite (never seen a bar on sats 33 or higher, the WAAS satellites, if I recall the numbers correctly). I'm guessing that being at roughly 40 degrees latitude, the WAAS geostationary satellites are just too far south for my receiver to get them, unless I sit out on a big lake or a cornfield.

 

Has anyone actuially acquired WAAS satellites from this latitude in wooded areas and such?

 

I routinely get WAAS corrections on my 60CSx and my ol' GPS V here in Morris County, New Jersey. I will lose WAAS reception and then get it back from time to time, but no problem receiving it.

 

I have not noticed a significant improvement in "accuracy" based on the WAAS corrections on the 60CSx. Even the reported EPE does not change much with WAAS reception (I have even seen the EPE increase). On my ol' V, WAAS will improve EPE by 5 ft or more, but the signal on the V is not nearly as reliable as the 60CSx.

 

Don't know if that is normal, but that's been my experience

[+scotte]

I think WAAS 48 is still not fully functional.

 

Yep, it's providing WAAS corrections but is not used as part of the position solution (i.e. it's ignored for ranging), as I understand it.

 

Remember the WAAS accuracy is only good if the geocache coord's were established with a WAAS enable GPS.

 

Not sure I agree with this statement. As a finder, your accuracy is as good as the sum of your error plus the error of the hider (and as a finder, certainly you have neither control nor knowledge of the latter). Whether or not WAAS was used in both cases is not really relevant - it may improve accuracy, but it's not portable (i.e. a WAAS correction only has meaning at a single point in time and space, but having a coordinate taken with WAAS enabled does not somehow become more useful only if that coordinate is subsequently used only with a WAAS enable receiver). (And maybe I completely missed your point. ).

 

Oh, and of course you can't forget that as soon as you represent the coordinate as DDD MM.MMM you can be no more precise than ~6 feet, so add that to the error sum as well!

 

I have not noticed a significant improvement in "accuracy" based on the WAAS corrections on the 60CSx. Even the reported EPE does not change much with WAAS reception (I have even seen the EPE increase). On my ol' V, WAAS will improve EPE by 5 ft or more, but the signal on the V is not nearly as reliable as the 60CSx.

 

Don't know if that is normal, but that's been my experience

 

I would say I've had the same experience between my GPSMAP 76 and my 76CSx. My 76 will routinely have EPEs of 7' with WAAS on, and my 76CSx never seems to get below 9-11' with it on or off - even with full bars, an external antenna, and clear view to the horizons. Maybe the EPE calculation is just more conservative in the CSx, or as you suggest the SirfIII is just so darn sensitive that WAAS may not matter. I admit I haven't played with it much on the CSx, as I did for the 76. Where I live, WAAS on the 76 was only effective fairly recently when they fixed the firmware to handle more than the first 2 WAAS enabled SVs.

Edited May 9, 2007 by scotte

[+apersson850]

The processors used in battery-powered devices like these aren't running all the time. If they don't have anything useful to do, they go into idle mode, which means they are powered up and ready to run as soon as needed, but they are waiting for an interrupt to start doing that.

Power consumption in idle mode is less than when executing code properly. As not using WAAS/Egnos implies less calculations to do, it does save you some juice in the battery. An entirely different, although related, issue is then that the nature of Egnos transmissions is such, that it can't be combined with the unit's power saver mode.

[vtmtnman]

I've got a GPS V,and I keep it turned off.No point to having it on in a place you can't get the signal.

[chondros]

So how do I know If I'm getting WAAS or not? Exactly what sattelite numbers are WAAS? I sometimes get a satalite number 53 (I believe). I assume that this is WAAS.

 

However I noitced that when this high number satellite shows up, my accuracy rate does not increase. In fact several times when I shut off the WAAS, my accuracy rate actually INCREASED? I live in Missouri.

[Team Marble]

Look at Post #10 on May 7 2007, 07:08 PM. In Missouri, you can get WAAS 35, 48 & 51. #47 covers the western US. east Asia and Australia.

[+dumketu]

I use the Garmin 60csx, and when using WAAS I have never gotten a better reading than I normally get with WAAS off. I can get about 9 feet accuracy on average either way. WAAS was more important for older, pre-SIRF GPSs.

 

Brian

[+NightPilot]

WAAS was not designed to provide greater horizontal accuracy. Its sole function is to provide greater vertical accuracy to aircraft flying precision (those with vertical guidance) instrument approaches. That's why the FAA commissioned it; the horizontal accuracy was already more than good enough for nonprecision approaches. Getting slightly better horizontal accuracy for finding caches is purely a biproduct of that effort. The ability to receive and process many more satellites is at least as important in increasing accuracy as is WAAS, and if you're receiving 10 or more satellites, then WAAS won't be of much more help.