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To WAAS or not to WAAS...

CacheCreatures

By CacheCreatures
in General geocaching topics

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CacheCreatures

+CacheCreatures

Posted
Posted

Yes, I realize this horse has been beat to death. I've read many of the previous posts regarding the topic. I understand the technology and the pros/cons.

 

What I'd like to know is

1) do you use WAAS?

2) If so, why? If not, why?

3) Has anyone tried an external antenna on the GPS V? Any improvement with WAAS reception (or for that matter general reception?)

4) Is there anything that can't be done if you don't decide to use WAAS? As in, are there caches out there that require the use of WAAS?

 

Thanks all icon_biggrin.gif

 

CacheCreatures are spreading... They can hide, but they can't run!

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Bloencustoms

+Bloencustoms

Posted
Posted

I leave WAAS on all the time on my vista. After using both a basic yellow etrex, and the vista with WAAS enabled, I notice a significant gain in accuracy. All of the caches I've found have been pretty close to home, so I really can't comment about it's performance elsewhere, but it works great here in Louisiana. Once I see a few "d's" on the signal bars, I know it's beginning to recieve corrections. I consistanly see epe's of less than ten feet.

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JMBella

+JMBella

Posted
Posted
Originally posted by Dream Alchemist:

I use WAAS on my Magellan SportTrak Pro, Why? Because I haven't looked at how to turn it off. Does it help? No not really, I am still just as lost. icon_confused.gificon_razz.gif

QUOTE]

 

Yep. That's me. My question is Whats the problem with WAAS? I have one player in my area that says, Don't post WAAS coords on my cache pages!

Example

 

Two roads diverged in a wood, and I-

I took the one less traveled by,

And that has made all the difference.

Because now I am Lost.

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iryshe

iryshe

Posted
Posted

What I'd like to know is

1) do you use WAAS?

 

No

 

2) If so, why? If not, why?

 

Doesn't work in Washington State (well)

 

3) Has anyone tried an external antenna on the GPS V? Any improvement with WAAS reception (or for that matter general reception?)

 

No. Haven't tried.

 

4) Is there anything that can't be done if you don't decide to use WAAS? As in, are there caches out there that require the use of WAAS?

 

No. But I don't think you're asking the right question. WAAS provides better accuracy when it works, so the better the accuracy the better chance you have of "getting warmer." But if the hider wasn't using WAAS then it may not help as much.

 

smile.gif Jeremy Irish

Groundspeak - The Language of Location™

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Criminal

+Criminal

Posted
Posted

quote:
Originally posted by CacheCreatures:

Yes, I realize this horse has been beat to death. I've read many of the previous posts regarding the topic. I understand the technology and the pros/cons.

 

What I'd like to know is

1) do you use WAAS?

2) If so, why? If not, why?

3) Has anyone tried an external antenna on the GPS V? Any improvement with WAAS reception (or for that matter general reception?)

4) Is there anything that can't be done if you don't decide to use WAAS? As in, are there caches out there that require the use of WAAS?

 

Thanks all icon_biggrin.gif

 

_CacheCreatures are spreading... They can hide, but they can't run!_

 

1. Yes

2. I can often get single digit accuracy readings. Also in Washington and it isn't great here, but certainly useable.

3. I use two, a small patch antenna on the roof of my car, and a slightly larger one (about the size of a deck of cards) on my truck. The one on the truck looks very much (exactly) like the one on the top of a C-141B.

4. No, and no.

 

http://fp1.centurytel.net/Criminal_Page/

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Team GPSaxophone

+Team GPSaxophone

Posted
Posted

Even if the hider was using an expensive surveyor's GPS that is accurate to 1cm, your search radius is still going to be about the same because it is based on the accuracy of your GPSr.

 

If you have one of those super-accurate GPSrs and the hider used a regular GPSr, you would still have the same search radius. The error is based on the hider's GPS accuracy.

 

Since 99.999999% of us use the standard models with about 15-20 foot accuracy, our search radius should be slightly more than the accuracy shown on the screen. Assume the cache was hidden with 15-20 foot accuracy and you'll be fine.

 

texasgeocaching_sm.gif Took sun from sky, left world in eternal darkness bandbass.gif

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leatherman

+leatherman

Posted
Posted

WAAS works great in all the parts of Western WA that I've been in.

cheeky-smiley-031.gif

Now that I've given the other side of this extreme generalization.

WAAS like any other satellite signal can be effected by terrain.

 

Most GPSr, that have it, are designed to operate with WAAS on. The battery life expectancy is projected with WAAS on. Your GPSr can not be less accurate because of WAAS.

 

Like Sax said, no matter how accurate your GPSr is the coords you are looking for may not be. I have been receiving 3 foot EPE all summer. However if the cache hider didn't take the time to record good coords, that 3 feet can't get me any closer.

 

Where's Eraseek? He always has something good to say about WAAS.

 

39197_3500.jpg39197_3600.jpg

POWDER!!!!!!

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outta here

outta here

Posted
Posted

quote:
Originally posted by Team GPSaxophone:

Even if the hider was using an expensive surveyor's GPS that is accurate to 1cm, your search radius is still going to be about the same because it is based on the accuracy of _your_ GPSr.

 

If you have one of those super-accurate GPSrs and the hider used a regular GPSr, you would still have the same search radius. The error is based on the hider's GPS accuracy.

 

Since 99.999999% of us use the standard models with about 15-20 foot accuracy, our search radius should be slightly more than the accuracy shown on the screen. Assume the cache was hidden with 15-20 foot accuracy and you'll be fine.

 

????

 

If the hider marked the cache with a 15-20 foot position error, and you returned to the point that the hider marked with 15-20 foot position error, you may be 40 feet away from the cache when your GPS reads 0ft. Yep your search area is over 5000 square feet. If the hider user a super GPS or ubertechneque with a standard GPS to mark the cache with only 5 feet of error, and you returned to where s/he marked w/ 20 feet of error, you are (at worst) 25 feet from the cache, and your search area is less than 2000 square feet. The same thing happens if the cacher marks w/ 20 feet of error and you are able to return to the actual position marked w/ only 5 feet of error) Cacher and finder's error must be added to determine how far you could be from the cache when the GPS says you are there.

 

To profit from the above, you you must start your search at the point wher your GPS reads 0ft from the cache position and methodically work your way out until you find it. Myself, I usually stumble about fairly randomly muttering curses, so it is no use to me.

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Deckyon

+Deckyon

Posted
Posted

1. I use WAAS

 

2. Why not try and be as acurate as possible? Some will argue about battery life and realistic accuracy and other things. The betteries I use are rechargeable and I carry 2 spare sets fully charged, more than enough to use the unit for 42 hours straight, with WAAS.

 

3. Do not ahve the GPS V

 

4. No, WAAS is not required.

 

---

Brad Buskey

http://www.deckyon.com

N38:17.281, W85:32.998

deckyon@NOSPAM.sturm.org

Magellan Meridian Platinum

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outta here

outta here

Posted
Posted

quote:
Originally posted by Team GPSaxophone:

Having 2 GPSr's with 20 foot accuracy on each does not double your search area. Your accuracy circle will overlap the other GPSr's accuracy circle. It is possible that the circles only barely touch (like the mastercard logo) but usually they will overlap better than that.

 

No, it more than doubles it. True, this assumes absolute worst case. But in life I have found that to be a fairly safe assumption. [icon_smile.gif]

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outta here

outta here

Posted
Posted

quote:
Originally posted by Team GPSaxophone:

It does not more than double it! Look at the Mastercard logo again. The circles OVERLAP. Any area inside of the overlapped part is not doubled, it is halved!

 

????

 

You completely lost me on that one.

 

If you place a cache, and the coordinates that you publish are 20 ft east of the actual cache location, and I plug your coordinates into my GPS which tells me I am at your coordinates when I am 20 feet east of the real location of your coordinates, I am now starting my hunt 40 feet from the cache. (That cache had better have a flag flying over it and occasionally send up flares, or I'll never find it)

 

Granted the opposite could happen. If your GPS reading is off 20 ft to the east and mine is off 20 ft to the west I'd be standing on the cache when it says I'm at your coordinates. But that would mean that the universe is a good and kind place, so I won't hold my breath for this to happen.

 

The expected case is somewhere in between. My original point was that all the accuracy you can manage when placing a cache is a help for the finder, even if the finder is returning to your coordinates with 20 feet of error.

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fizzymagic

+fizzymagic

Posted
Posted

People, people, people.

 

GPS accuracy estimates are not hard circles; they are roughly Gaussian probability distributions. So everybody is wrong in this debate.

 

The correct answer is considerably more complicated, since in general the "accuracy" estimates of GPS receivers are not the standard deviations of these Gaussians. If they were, then the answer is pretty straightforward. Assuming they are, then the expected error is just

sqrt(e1^2 + e2^2)

So for a 20-foot error on both devices, the expected error would be about 28 feet.

 

Now back to the examples:

  • hider error = 30 feet, finder = 30 gives a radius of 42 feet.
  • H = 30, F = 15 => 33
  • H = 15, F=15 => 21

 

If you really want to do a mathematical model of the required search time, you should estimate the length of a spiral search pattern from your zero point to the expected cache radius. But I'm not going to do that.

 

I always use WAAS, because the Magellan method for including it never decreases the accuracy of the reported position and because on Magellan receivers it does not affect power consumption. If I had a Garmin receiver, I might have different behavior.

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RJFerret

+RJFerret

Posted
Posted

quote:
Originally posted by CacheCreatures:

Yes, I realize this horse has been beat to death.

 

That's for sure...and how I came to my conclusions.

 

quote:
What I'd like to know is

1) do you use WAAS?

 

No.

 

quote:
2) If so, why? If not, why?

 

Since caches weren't generally hidden with such great accuracy, there's no value.

 

quote:
3) Has anyone tried an external antenna on the GPS V? Any improvement with WAAS reception (or for that matter general reception?)

 

Of the articles and websites talking about external antennas, they all indicated improvement across the board.

 

quote:
4) Is there anything that can't be done if you don't decide to use WAAS? As in, are there caches out there that require the use of WAAS?

 

No and no. (At this point in time, only one pending not-found I haven't returned to yet...)

 

Personally, for geocaching, as I've said before, I believe WAAS is overkill.

 

HTH,

 

Randy

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Xitron

+Xitron

Posted
Posted

quote:
Originally posted by fizzymagic:

People, people, people.

 

GPS accuracy estimates are not hard circles; they are roughly Gaussian probability distributions. So _everybody_ is wrong in this debate.

 

The correct answer is considerably more complicated, since in general the "accuracy" estimates of GPS receivers are _not_ the standard deviations of these Gaussians. If they were, then the answer is pretty straightforward. Assuming they are, then the expected error is just

sqrt(e1^2 + e2^2)

So for a 20-foot error on both devices, the expected error would be about 28 feet.

 

Now back to the examples: + hider error = 30 feet, finder = 30 gives a radius of 42 feet.+ H = 30, F = 15 => 33+ H = 15, F=15 => 21

 

If you really want to do a mathematical model of the required search time, you should estimate the length of a spiral search pattern from your zero point to the expected cache radius. But I'm not going to do that.

 

I always use WAAS, because the Magellan method for including it _never_ decreases the accuracy of the reported position and because on Magellan receivers it does not affect power consumption. If I had a Garmin receiver, I might have different behavior.

 

ummm yea what he said.

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GT-5

GT-5

Posted
Posted

quote:
Originally posted by CacheCreatures:

 

What I'd like to know is

1) do you use WAAS?

2) If so, why? If not, why?

3) Has anyone tried an external antenna on the GPS V? Any improvement with WAAS reception (or for that matter general reception?)

4) Is there anything that can't be done if you don't decide to use WAAS? As in, are there caches out there that require the use of WAAS?

 

_CacheCreatures are spreading... They can hide, but they can't run!_

 

1. No

2. It does not seem to work well here in Utah.

3. No

4. No

 

------------------

GT-5

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Xitron

+Xitron

Posted
Posted

I always use wass for the simple reason I never was interested enough to turn it off. After reading some of the posts though I got interested and checked Magellan's web sit and found I was using outdated software on my GPS. I downloaded and installed the software tonight. A little off topic, but just a heads up. I've only had my GPS since July but who knows how long it was sitting on the store shelves. Maybe updating you software will improve the wass reception?

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RJFerret

+RJFerret

Posted
Posted

quote:
Originally posted by Xitron:

I always use wass for the simple reason I never was interested enough to turn it off.

 

This fits with many people I've talked to at events who never turned it off, but couldn't answer whether they regularly get WAAS signals here in CT.

 

On your comment re: software, yes. I know someone mentioned the Garmin software update for the Map76 series did improve WAAS reception. Having geocached along with someone who has one of those units (which features the same antenna as Magellan's instead of the patch in my eTrex), I can tell you the 76 had horrible regular sat reception (never mind WAAS) in the woods. (Worked fine at our beach event.)

 

I think, CacheCreatures, if you are wondering whether WAAS will do good for you, as long as you have a clear view of the horizon regularly (not much foliage, hills, etc.) then you might be able to take advantage of it. However, again, it's not going to affect geocaching much due to the hiders coords.

 

Enjoy,

 

Randy

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leatherman

+leatherman

Posted
Posted

quote:
Originally posted by LowranceTracker1:

WAAS is not good in heavy tree cover in North America.

 

There are no real trees in Texas. Just bushes that people have nicknamed trees.

 

WAAS works fine way up here in Washington. Where there are real trees.

 

If your going to bring an argument to the table, bring one that makes a little sense.

 

39197_3500.jpgPOWDER!!!!!!

19490_2600.gifHonored to provide inmate labor for Admin brick manufacture since 2002.

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DARC

DARC

Posted
Posted

1) do you use WAAS?

 

Yes when whenever I can.

 

2) If so, why? If not, why?

 

Part of the joy of Geocaching is to have an excuse to use technology outdoors. To try and get the best accuracy out of the tool and compare notes how others did and why. WAAS simply gives you more accuracte results.

 

3) Has anyone tried an external antenna on the GPS V? Any improvement with WAAS reception (or for that matter general reception?)

 

Street Pilot 3 gets much better reception with external antennas. Even better still if you raise it a few feet on a pole or stick. SP3 does't have WAAS reporting but I'd expect similar improvements with the V.

 

4) Is there anything that can't be done if you don't decide to use WAAS? As in, are there caches out there that require the use of WAAS?

 

WAAS improves the degree of confidence in your position readings. When a cache is found, you can tell if the position error is because of you or not.

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LowranceTracker1

LowranceTracker1

Posted
Posted

quote:
Originally posted by leatherman:

quote:
Originally posted by LowranceTracker1:

WAAS is not good in heavy tree cover in North America.

 

There are no real trees in Texas. Just bushes that people have nicknamed trees.

 

WAAS works fine way up here in Washington. Where there are real trees.

 

If your going to bring an argument to the table, bring one that makes a little sense.

 

http://www.geocaching.com/profile/default.asp?A=39197_POWDER!!!!!!_

http://img.Groundspeak.com/cache/19490_2600.gif _Honored to provide inmate labor for Admin brick manufacture since 2002._

 

Never brought an argument to the table. It's common knowledge on GPS manufacturers web pages. Since when is height a requirement for coverage? It's not, and I know all about trees, my dad was a logger.

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