To WAAS or not to WAAS

[+Ima90sjezus]

I just recently purchase a Garmin Etrex Vista, and I have located my first two caches. Although I do not know any of the advanced features yet, I headed out with the idea of "It can't be that difficult". Well the "basics" are not difficult. I now want to know how to use my Vista COMPLETELY. But here is my question for now, should I turn on WAAS (which drains the battery faster) or should I just not bother with it. Any suggestions on this and other features of the Vista would be a GREAT help.

 

TIA,

Ima90sJezus

[Couch_Potato]

I have a Legend and I've not noticed a significant difference with WAAS off or on. Typical accuracy either way is around 10m.

 

I'm not lost!

I just don't know where I am.

[+KYtrex]

I keep WAAS off most of the time. I have played around with it and most of the time I get an accuracy about the same whether it is on or off. I have noticed that whenever you get under tree cover, WAAS will actually make your accuracy worse. Try a search of these forums with "WAAS" in the "Search Words" box and you should find all the information you could want about WAAS.

The seach function is one of the most handy tools I have found on these forums.(Besides the "Instant Graemlins )

[+KYtrex]

I keep WAAS off most of the time. I have played around with it and most of the time I get an accuracy about the same whether it is on or off. I have noticed that whenever you get under tree cover, WAAS will actually make your accuracy worse. Try a search of these forums with "WAAS" in the "Search Words" box and you should find all the information you could want about WAAS.

The seach function is one of the most handy tools I have found on these forums.(Besides the "Instant Graemlins )

[+Zartimus]

I just leave it on most of the time. I haven't noticed a big drain on the batteries (Recharable NIMH's).

 

I try and hit Sat 35 by pointing at the horizon if i get a clear field of view, especially when setting cache co-ordinates. I like seeing d's on most of the bars. I get 5-6m accuracy. I should realy test it more thorouly though like some of the preceding posters. Take multiple readings with WAAS on and then off to see the results.

 

If i see a diff I'll post the results.

 

Cheers!

[+mrp]

My understanding is that the battery drain associated with WAAS is pretty small, and won't greatly affect battery life. However, the bigger issue for me is that here in northern Califonia, the geometry of the two visible WAAS satellites is such that I can slmost never get a lock, and leaving WAAS on means that two slots of my 12 channel receiver are always dedcated to satellines that I can't get, pushing out two other satellines that I might be able to receive if I had WAAS turned off. So.. unless I am in a location with exceptionally good southwesterly views and I really need the differential corrections that WAAS provides, I leave it turned off.

 

-- Mitch

[+fizzymagic]

quote:

---

My understanding is that the battery drain associated with WAAS is pretty small, and won't greatly affect battery life. However, the bigger issue for me is that here in northern Califonia, the geometry of the two visible WAAS satellites is such that I can slmost never get a lock, and leaving WAAS on means that two slots of my 12 channel receiver are always dedcated to satellines that I can't get, pushing out two other satellines that I might be able to receive if I had WAAS turned off.

---

 

First, you are correct about the power drain; the additional drain from WAAS should be negligible.

 

But I live near you, and I rarely have any trouble locking on the WAAS satellites around here. Whether they do much good or not is another question, but I've been able to lock on both with a good southern view, and one under moderate tree cover. Also, since the WAAS data is good for about 5 minutes, spotty reception is just fine.

[+mrp]

quote:

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Originally posted by fizzymagic:

 

But I live near you, and I rarely have any trouble locking on the WAAS satellites around here.

---

 

Yeah.. I think we discussed this in an email thread about Magic Trig. I think the the difference is the Antennas of our respective units. My little etrex legend has a patch antenna, which is much less sensitive than the quad antenna on your unit. Probably doesn't make that much difference for satellites with with clear skys and low hour-angles (astronomy term), but under tree cover or when low in the sky (high hour angle), it probably makes the difference.

 

But since this question was about a vista (basically the same setup as the legend, for our purposes), I stand by my assertion that it's not much use here, at least with the legend/vista/venture line. Owners of WAAS enabled Magellans and those Garmins with quad antennas probably have much better luck.

 

I like the look of the new SportTrak series, though it sound like they've taken the lawyer screen to extreme lengths.

-- Mitch

[+cachew nut]

quote:

---

Originally posted by Pneumatic:

My understanding is that the battery drain associated with WAAS is pretty small, and won't greatly affect battery life. However, the bigger issue for me is that here in northern Califonia, the geometry of the two visible WAAS satellites is such that I can slmost never get a lock, and leaving WAAS on means that two slots of my 12 channel receiver are always dedcated to satellines that I can't get, pushing out two other satellines that I might be able to receive if I had WAAS turned off. So.. unless I am in a location with exceptionally good southwesterly views and I really need the differential corrections that WAAS provides, I leave it turned off.

 

-- Mitch

---

 

I don't believe it will work the way you describe, but then I'm not using an Etrex. You only need a lock on four satellites to get a position. If you are receiving a WAAS signal, your accuracy will improve. I use a Meridian Gold by Magellan. Here's how they describe it:

Meridian Gold finds your location by tracking up to 12 GPS satellites simultaneously. Assisted by the U.S. Wide Area Augmentation System (WAAS), the Meridian Gold is accurate to within 3 meters or better.

[+Renegade Knight]

WAAS noticbly slows down my GPS functions so I leave it off. 95% of the time I don't use it because once I'm within 15' of a cache where to look is pretty obviouse and WAAS won't make any difference.

[+mrp]

quote:

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Originally posted by cachew nut:

 

You only need a lock on four satellites to get a position.

---

 

True, but knowing which 4 is the trick. Picking any random 4 out of the visible constelation won't necessarily give you good answers. Some may be blocked by buildings, trees, the geocacher leaning over the device, etc. Signals from one satellite may have passed through a particularly bad part of the ionosphere and become garbled or refracted. Also some configurations give better answers than others. The more angular separation between the satellites the less the DOP (dilution of position).

 

After all.. if 4 sats were enough, then we'd all have 4 channel receivers. :-) If you decrease the number of satellites at your disposal, then you decrease the odds of getting a good configuration from those you can receive. If WAAS is working properly, this will offset the loss of a couple of other satellites, but like I have said before.. I've only once gotten WAAS corrections to work in over a year of trying. And that was after standing still for 20 minutes to allow it to download the WAAS data (need 10 minutes uninteruptted, and regular updates thereafter).

 

quote:

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If you are receiving a WAAS signal, your accuracy will improve.

---

 

Not necessarily, according to the document I read, if you're not receiving distance of one of the ground stations (for instance, most of Europe), then using WAAS may cause a decrease in accuracy.

 

Also, be somewhat skeptical of claims made by the marketing depts. Usually these statements are "defensible", but overly optimistic.

 

-- Mitch

[vagabond]

I keep it off in my Magellan gold I seem to get more accurate readings with it off.

Comparing against a Lowrance GN 212 with it on the Lowrance beats the magellan about 3/4 of the time, with it off its about 50 50

 

All who look are not lost

[vagabond]

I keep it off in my Magellan gold I seem to get more accurate readings with it off.

Comparing against a Lowrance GN 212 with it on the Lowrance beats the magellan about 3/4 of the time, with it off its about 50 50

 

All who look are not lost

[+fizzymagic]

quote:

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Originally posted by vagabond:

 

Comparing against a Lowrance GN 212 with it on the Lowrance beats the magellan about 3/4 of the time, with it off its about 50 50

---

 

How are you measuring the accuracy? Unless you are measuring against a known position (obtained by some method other than another GPS receiver) then you aren't measuring accuracy, you're measuring precision or repeatability.

 

WAAS is supposed to improve accuracy; it should have no effect on stability. It might have an effect on repeatability, but measuring the effect would be quite difficult.

[mdmax371]

I use WAAS all the time wouldn't leave home without it!

[+Mudfrog]

WAAS doesnt seem to make much difference when enabled on my GPS76. It shows that i lock on fine but i cant tell any difference in operation. Havnt enabled it at all for caching...

[+Prime Suspect]

Until more WAAS satellites are put up, for caching purposes it usually better to leave it off. Garmin units (and probably Mags as well) will not mix WAAS enhanced data with non-WAAS data to determine a location. So if you've only got WAAS data for 2 satellites, the unit will ignore that. If you've got a lock on 9 satellites (which is pretty good), but only have WAAS data for 4 of them, the unit will only use the 4 WAAS enhanced signals, and will ignore the other 5. If the 4 form a poor constellation, you very well may get a less accurate location reading than had you turned off WAAS and allowed the unit to use all 9 satellites.

 

But if you've got open sky, and enough time to collect WAAS for all the satellites you have a lock on, you will definitely get more accurate readings.

 

Once you understand how your unit works with WAAS, you can determine when to use it, and when not to.

 

[BassoonPilot]

I use the Vista, and leave the WAAS disabled. It just doesn't seem to make an appreciable difference.

 

With WAAS enabled, my Vista appears to drain the batteries much faster ... when I have used the Vista set to Normal/Enabled/Compass On, the batteries have typically lasted less than three hours. Set to Normal/Disabled/Compass On, the batteries seem to last at least twice as long.

 

I also noticed that with everything enabled, when the "batteries low" warning comes up, disabling WAAS sends the notice away for about an hour, and disabling WAAS and Compass for 1 1/2 - 2 more hours.

[+st_richardson]

I have a Garmin Vista and use WAAS all the time.

[+apersson850]

Well, while using WAAS, you have to run the unit in normal mode. If you disable WAAS, you can use the battery save mode, which will give you about 50% more battery life.

 

I agree with those who have noticed that receiving WAAS signals does slow the unit down. Maybe especially if the reception is rather bad.

 

I don't use WAAS, since I'm in Europe. The European counterpart, EGNOS, is not fully operational. I can receive sat #33, but it doesn't transmit any information which the unit wants to use. They say that's because there is a status signal saying "don't use", and the Garmin units adhere to that. Magellan units are said to disregard that status signal, and use the information, for what it's worth.

 

The best EPE I've seen on my unit is four (4) meters. When I was in France, I could get WAAS satellite #35, but that did of course nothing to improve my accuracy, since the related ground stations were all on the other side of the Atlantic.

 

Anders