WAAS...do You Really Need It?

January 30, 2004

You guys did such a good job of answering the battery question I thought I would throw another one at you.

I have the eTrex, no WAAS. So how important is it to have WAAS.

I have found a few caches without a lot of trouble so I wonder if WAAS is worth me selling my one week old eTrex and stepping up to something with WAAS.

I live by a major city (OKC) and in a pretty flat part of the country, is this more ideal for GPS reception and therefore is WAAS (that's funny "is waas") not as much benefit.

I looked at the FAQ's and did a search but did not find a solid answer to my specfic question, "how benficial is it to have a GPS with WAAS".

I guess what I'm asking is for a from the basics to the finish education on WAAS.

Thanks

Thumper :blink: :blink:

My english comp prof would have a cow over this, is WAAS, if WAAS, with WAAS, oh man I'm getting dizzy........

January 30, 2004

There are many cachers out there who don't have WAAS capability and they do just fine finding caches.

Learning to think like the cache hider will help you much more than the extra few feet closer to the cache that WAAS will get you. Besides, if the hider didn't have WAAS, you will have to deal with that error anyway.

January 30, 2004

I haven't used my waas very often, usually because that last satellite won't hook up very often. When it did, I got some pretty impressive accuracies (like 10 feet), but still found myself shoving the GPS in my pocket so I could concentrate on looking at the ground. It is just too darn temping to stumble around looking at the GPS display!

January 30, 2004

I leave WAAS turned on and can get some nice accuracies. I have gotten 7-8 ft acc on clear days. I havent yet turned WAAS off on my GPS to see how it does. But it doenst seem to make that much of a difference in treecover WAAS isnt all that helpful, so your just fine without.

Edited January 30, 2004 by Amazingracer

24.7k · January 30, 2004

I keep WAAS turned off. It hasn't caused me much problems.

4k · January 30, 2004

Tried to use it once or twice....not impressed enough to do it again. If I get within 50 feet of a cache without it, having it on ain't gonna help me that last 50 feet, because I'm usually just looking around the area and not at the GPSr. WAAS is vastly overrated for handheld GPSrs.

(Let the flames begin)

9.5k · January 30, 2004

I tend to leave it on. If it is as others say turning off doesn't affect the results, then leaving it on also doesn't affect the results. Saving on battery energy is academic if you're carrying spares as any geocacher normally would anyway.

2.7k · January 30, 2004

I use WAAS and have doen some caches that actually required it! One cache in Redmond had me getting coords down to 8 feet in order to calculate the final coords. Very well done hide by FiendorFoe...Check and check again or something like that. I always try to get it down to 8-14 feet if I can when hiding caches. Otherewise, readings in the low 20s will work for me.

January 30, 2004

This is a good question.

When I was searching for info on which GPS to buy I knew I wanted WAAS

Why ? Because it gives such good accuracy.

Right ?

Well...

Not exactly.

When I turn on WAAS on my unit...

I don't get any better accuracy at all.

My unit cannot be in Battery Saver mode.

So I don't get any closer, and go through batteries every couple of hours.

You tell me if it's worth it.

Have yet to fail finding a cache because of not using WAAS.

Have missed a few because I am too dense to realize where to look.

1.4k · January 30, 2004

So how important is it to have WAAS.

That debate again.

To summarize, some feel that the way WAAS is implemented tends to cause the coordinates to "wander" a lot more then with it off. Some will say it uses batteries more. Apparently WAAS is incompatible with battery saver. From my own experience it does suggest that WAAS could well cause excessive motion of the coordinates.

3.9k · January 30, 2004

I keep WAAS on. From what I've heard it varies depending on your location as far as if it helps or hurts. You may just need to experiment in order to find out for yourself. Here's more info on WAAS.

1.2k · January 30, 2004

I leave it on. I have found that with WAAS I get to within 3 metres without 5 to 7 metres. Not much of a difference but I like it, definitely not necessary for caching.

1.8k · January 30, 2004

WAAS seems to drain the battery faster. Also (for me, anyway,) it doesn't seem to work well in the woods, but prefers to be in a more open area, such as out on the water.

January 30, 2004

When I get time (and this could be a while considering imminent fatherhood), I intend to mark a point as if it were a cache, then approach it with and without WAAS. In a psuedoscientific way, I'll test things like:

1. Speed of update (when I turn away from a waypoint, how quickly does the compass and distance update)

2. Repeated accuracy tests

3. Amount of "jumping around"

I'll probably try to do this under tree cover with patchy WAAS signal (new england) and in the open. Course the results would only really apply to my GPSr and my latitude.....

January 30, 2004

Once again you have come to my rescue. From what I read the people that do have WAAS are divided on it's usefulness, some pro, some con, and some not sure. After reading the links provided and your inputs I think I will just stick with the eTrex. After all I have found all of the caches I went after with the eTrex. The only cache I missed was with a loaner GPSr that is a high end unit so it might have had WAAS, and I don't know if it was turned on or off. Might have been on as the owner told me he only gets a few hours out of his batteries. I might suggest to him that he turn WAAS off to save on cells.

Thanks

Thumper :blink:

4k · January 30, 2004

Once again you have come to my rescue. From what I read the people that do have WAAS are divided on it's usefulness, some pro, some con, and some not sure. After reading the links provided and your inputs I think I will just stick with the eTrex. After all I have found all of the caches I went after with the eTrex. The only cache I missed was with a loaner GPSr that is a high end unit so it might have had WAAS, and I don't know if it was turned on or off. Might have been on as the owner told me he only gets a few hours out of his batteries. I might suggest to him that he turn WAAS off to save on cells.

Thanks

Thumper

OKThumper.....the most, and I cannot stress this enough, important thing is to HAVE FUN!!!!!!!!!!!!!!!!!!!!!!

1.8k · January 30, 2004

Once again you have come to my rescue. From what I read the people that do have WAAS are divided on it's usefulness, some pro, some con, and some not sure. After reading the links provided and your inputs I think I will just stick with the eTrex. After all I have found all of the caches I went after with the eTrex. The only cache I missed was with a loaner GPSr that is a high end unit so it might have had WAAS, and I don't know if it was turned on or off. Might have been on as the owner told me he only gets a few hours out of his batteries. I might suggest to him that he turn WAAS off to save on cells.

Thanks

Thumper

And you're going with a Garmin, so you shouldn't have any trouble getting to where you want to go anyway!

Wait, did I just type that out loud... :blink:

January 30, 2004

I have found a few caches without a lot of trouble so I wonder if WAAS is worth me selling my one week old eTrex and stepping up to something with WAAS.

No, I wouldn't upgrade. Your eTrex should do just fine in terms of letting you find caches. I think it's most useful for hiding caches anyway - that's when you really would like to minimize the error in your GPSr readings as much as is possible. (When I hide a cache, I use WAAS and auto-average the coordinates for 5-10 minutes after the GPSr has stabilized. I get few complaints about errors on my waypoints.)

If I were going to upgrade, the thing I think is more useful than WAAS is mapping. This may be more or less useful to you depending on where you live. I've got a GPSMap 76s, and I just recently bought the mapsource metroguide USA CD for it. I live in Dallas, TX, and our streets run in more or less random directions, so having the maps on my GPS is incredibly useful. (Imagine a town built entirely by realtors who were having a contest to see who could design the most confusing subdivision after drinking 3 or 4 martinis - that's Dallas.) There've been several caches I've completed recently that I easily found, that some of my friends (who are way better, more experienced cachers than I am), had difficulty with just because they couldn't easily find the roads to get near the cache.

Obviously, if you live in a rural area with 10 roads that show up on the map anyway, or live in a city that was designed by people who were sober at the time, this is a whole lot less useful.

If you get a mapping GPS, it will most likely have WAAS support anyway. But it's really not neccessary.

4k · January 30, 2004

(Imagine a town built entirely by realtors who were having a contest to see who could design the most confusing subdivision after drinking 3 or 4 martinis - that's Dallas.)

That explains a lot!!

January 30, 2004

At least the roads provide us some sort of a terrain challenge - if you load the topo maps for the area onto your GPSr, they all just say 'dude - it's flat!'

January 30, 2004

It just depends on if you can get a signal from one of the two WAAS sattelites. FYI, more WAAS sattelites will be launched in teh next few years, making it MUCH more useful.

January 30, 2004

Where I live I just don't get WAAS very often -- too mountainous. When I do get WAAS the estimated accuracy as displayed is usually < 10 feet, but do not ever rely on that EPE as anything resembling reality. Just because it says 10 feet does not mean you are really within 10 feet of the coordinates. The standard joke is Garmin uses a random number generator to determine the displayed EPE.

4k · January 30, 2004

I hid my second cache today, and it was in heavy timber. Without WAAS, I had an accuracy reading of 8 ft!!!!!! That's the second best I've ever had, the best being 7 ft out in the open on a clear day.

January 30, 2004

Mr. Benchmark

I live in Dallas, TX, and our streets run in more or less random directions, so having the maps on my GPS is incredibly useful.

Funny guy. I live in OKC and have been to the big D on several occasions. I fould it most useful to have a few before going anywhere down there. I do have the Earthmate with SA 2004 and I find it is really helpful in getting me to the right area for the eTrex to take over. Yes a mapping GPS is the only way to go. I got it for trips in the RV but find I use it more for geocaching.

Maybe in a few years when more WAAS units are in the air we will be able to use the WAAS stuff better. By then I might be ready for an upgraded unit.

Thanks all

Thumper :blink: :cute:

Here all the time I thought Dallas was laid out by following a drunk snake.....................or a new geocacher finding their first cache.......................with a loaner GPSr. (me) :blink:

1.8k · January 31, 2004

I thought WAAS was primarily used for flying....gives the airplane a reference to the ground as well as its position over the ground. The WAAS Signal actually is transmitted from the Ground Station. So, if you can't "see" it with your GPSr (line of site,remember) it won't do you any good. Someone else mentioned this: there are not too many of those ground stations operational at this time.

Have'nt posted lately, so thought I could add something to this thread.

Don't sweat the WAAS.......

JayBee

4.4k · January 31, 2004

10 times more acuurate..........................I do !!!!!!!!!!

WASS

3.5k · January 31, 2004

I thought WAAS was primarily used for flying....gives the airplane a reference to the ground as well as its position over the ground. The WAAS Signal actually is transmitted from the Ground Station. So, if you can't "see" it with your GPSr (line of site,remember) it won't do you any good. Someone else mentioned this: there are not too many of those ground stations operational at this time.

Have'nt posted lately, so thought I could add something to this thread.

Don't sweat the WAAS.......

JayBee

Wrong!

WAAS is transmitted from Satellites. The corrections are made and modeled by master stations and transmitted through the WAAS sats. These corrections are then applied by YOUR GPS depending on YOUR position.

Wrong. One WAAS sat will transmit the same corrections almanac that two will. More WAAS sats just give better exposure.

Wrong.

WAAS will not make your postion wander more. This is caused by things such as multipathing and lousy sat configuration.

No.

You don't need WAAS.

Yes.

I use it most all the time, and like it.

January 31, 2004

10 times more acuurate..........................I do !!!!!!!!!!

WASS

Don't put too much stock in that article. It isn't technically accurate.

I haven't heard of WAAS going global anytime soon, if at all. Much of the US doesn't even have redundant coverage (there are only 2 sats transmitting WAAS data), let alone the ocean blue.

George

1.1k · January 31, 2004

10 times more acuurate..........................I do !!!!!!!!!!

WASS

Not totally correct. Global WAAS? not any time soon or even any time latter.

Also Raytheon are only the primary contractors and actually got the job by default and aren't the initial contractors awarded the project.

Cheers, Kerry.

January 31, 2004

i keep the waas on.i like it better that way .

4.4k · January 31, 2004

Well I wonder why the Link would say that a Wass GPS is 10 times more accurate than a regular GPS.

Is that some of that old conspiracy again,or what?

Pun intended Kerry I haven't heard from you in a while.

I could place many more links and I have 1st hand experience with that type of acurracy with my Wass GPS,several times now with Federal,State and Local GPS Survey's. :rolleyes:

January 31, 2004

On what do you base the "10 times more accurate", other than what that faulty article says?

WAAS is advertised as getting you within 3 meters. "Regular" GPS reception today is said to be within 15 meters. From that I get a factor of 5, not 10.

Even that assumes WAAS under optimum conditions, which often don't exist on the ground.

George

4.4k · January 31, 2004

Numbers Expotentials Sine Cosine Least square

Well you have me in a way there.........I am assuming from this article and other published data.

Which I have no proof of authority,and your rebuff which I have no proof of authority.

Actual Readings from the Several systems..IE Federal,State and Local GPS Readings on the Spot.

When marked and gone back to are within <1-3.5 feet variation on MY GPS.

that is on distance to p[oint at p[oint.

I wish I had the $$$ to verify all my findings,and the Equiptment to monitor and a place to publish this data. It is word of mouth as yet,but someday will become available.

I have been looking into this for many years now and it has slowly been DE-**********.

I know some things that most do not and have proved it to myself as well as others,and I do not have to prove it to any other persons, it will reveal itself.

And in the future we can look back to this post,and discuss it further.

Untill then I am happy with the Wass and it's acurracy.and looking forward to future applications.

Happy................................................................Geotrails

January 31, 2004

GEE WHIZ, play nice guys!

But I see points on both sides. I will stick with the eTrex for now, and maybe consider a WAAS compatable unit later when I upgrade.

Thumper :rolleyes: <_< <_<

January 31, 2004

Tangent, Secant, Cosine, Sine!

3.14159!

I won't claim to have mystical technological knowledge yet unknown to the masses, but my son and I are planning to compare non-WAAS and WAAS readings this weekend as part of his school science project (6th grade level, so we're not going to be spending big bucks, time, or using extreme math).

We're going to take several readings over time on a particular spot in an open area, where WAAS availability won't be a problem. I'm guessing that the WAAS data points should be clustered in a tighter circle than the non-WAAS readings. The thing I'm really interested in is how well the results compare to the "advertised" specs of a consumer GPS (in this case, the test units will both be Garmin...one with WAAS enabled, one without).

George

January 31, 2004

nincehelser:

but my son and I are planning to compare non-WAAS and WAAS readings this weekend as part of his school science project

Please post your findings here, I would like to see what y'all came up with.

Thumper :rolleyes: <_< <_<

4.4k · January 31, 2004

NASA

The NASA channel has a current program on the GPS and it goes into explanation and details and they also state that the GPS (Recreational) can be within centi-meters of accuracy.

I am no Math Wizard but have some Mathmatical Projects (Theories)that I have been working on for over 20 years,and still do not quite fully comprehend, nor can I relay the concepts fully to another.

The things I know have been made public here in the forums it is up to other to figure it out.

When Selective Availability was turned on this was the way around the Psuedo Random Code,That is averaging your daily readings and throwing out the obvious errors.

You are doing what I have been doing for quite a while.

I use the Triangulation Stations for the Control,as well as another Geoid Model I Have been using.

I use the Readings that I get from the Satts at the Stations,they are Trilateration,not Triangulation.

I guess there are so many unaswered questions because the question just has not been asked yet.

The Theory is based on the Universe as a Mathmatical Whole,held together in a precise order and time,

which in turn creates the 360 degrees in a Circle,Year(Biblical) not (Julian),24 divisions of the 360,then the 7 divisions,notes,colors,scale,techtonic plates..............Well the more you look the more you find how this is done Which goes back to Einstiens E=MC2 the Energy inherent in all matter....are all linked to Electricity and magnetism,and all types of radiation are the same things just a diffrent frequency and vibration,which in turn goes back to the Ancient Philosophers.

edit: add link

Edited January 31, 2004 by GEO*Trailblazer 1

1.1k · January 31, 2004

The NASA channel has a current program on the GPS and it goes into explanation and details and they also state that the GPS (Recreational) can be within centi-meters of accuracy.

GPS (recreational) accuracy within centi-metres, then obviously some don't have any understanding exactly what recreational GPS accuracy is, actually what accuracy is at all.

Averaging and actual recreational GPS accuracy aren't in any way even related.

Since I really didn't make specific mention of this 10 times more accurate, then perhaps you'd like to specify the official accuracy spec for both GPS and WAAS.

Geoid model? come on what's a geoid model got to do with GPS accuracy?

Cheers, Kerry.

4.4k · February 1, 2004

GPS is calculated by Trilateration. Correct?

That is it takes 3 points, a triangle or geoid to trilaterate not triangulate it and your position.

February 1, 2004

nincehelser:
but my son and I are planning to compare non-WAAS and WAAS readings this weekend as part of his school science project

Please post your findings here, I would like to see what y'all came up with.

Thumper

Will do. We've just been taking reading for a short time, and my initial take is that I'm suprised how close the WAAS and non-WAAS readings are so far. Perhaps it will vary more over time as the sat positions change.

Elevation readings seem the most erratic as would be expected, but I'm not sure how much the Vista's barometer is impacting that. I can't seem to figure out how to turn that feature off. I tried turning off "auto calibrate", but then the elevation readings were really screwy. If I leave it on, both elevation readings seem reasonably close to each other.

One thing I noticed as the temperature is falling...both units are sitting directly on the concrete patio, and are getting kind of chilled (it's about 53 degrees F right now). The yellow eTrex display seems to be slowing down, while the Vista still seems normal. We started both units with fresh batteries out of the same package.

This isn't exactly what we want to measure, however, so I put both units on a small plastic box to insulate them somewhat from the concrete.

Update: I boosted the display contrast on the yellow eTrex substantially. Now it seems readable and normal. I've never had to do that before.

George

Edited February 1, 2004 by nincehelser

4k · February 1, 2004

Zzzzzzzzzzzzzzzzzzzzzzzzzz..........................<snort>..............<whinney>..........sorry, just bored...it's snowing....will that have any effect on WAAS?

Does voltage have any effect on WAAS? If so, wouldn't the right hiking boots make a difference in your readings? Say for instance, you were wearing leather soled boots as opposed to rubber soled boots. The rubber soles would work better as an insulator against static electricity, thus keeping rogue electrical surges from the GPSr. Unless it's snowing, like it is now...then you'd be wet.....and you'd still conduct electricity....though the static part wouldn't be as great due to the humidity. Unless your caching vehicle slid off the road and hit an electrical pole and got stuck, and you got out and stepped on the downed line.......and if you were near a riding stable, other horses could get out, then there would be more dead ones to beat. But, you could make it a virtual, providing a locationless wasn't already nearby to rule out your traditional. But, would a dead horse actually be able to conduct electricity to a GPSr 528 feet away, taking into consideration the effect played out by the curvature of the earth? Anyone? Hello?

Edited February 1, 2004 by Sparky-Watts

4.4k · February 1, 2004

Acurracy, Precision and Errors

To Keep us all on the same page.

In dealing with measurements it is important to distinguish betwenn accuracy and precision.

as stated by Kerry.

As defined by the American Society of Civil Engineers,accuracyis "absolute nearness to the truth" whereas precision is "relative or apparent nearness to truth."(Formerly ASCE defined precision as "degree of fineness to reading in a measurement,or,the number of places to which a computation is carried.")

As defined by the U S Coast and Geodetic Survey,accuracyis "degree of conformity with a standard" whereas precisionis "degree of refinement in the performance of an operation or in the statement of a result."From these mutually consistant definitions it follows that a measurement may be accurate without being precise,and visa versa.

Example:

a distance may be measured very carefully with a tape to 1/1000 of a foot,and still be in error of several 1/100 of a foot because of erroneous length of tape;the measurement is precise but not accuarte.

# 3 errors : Temperature variations,

in the phenomena of nature such things as temperature,gravity,refraction,magnatism.........all have their effects.

February 1, 2004

C'mon. You must be the Dr. Bronner of Dr. Bronner's Soap fame? It's sure seems like I'm reading one of his labels.

"All-One!"

George

4.4k · February 1, 2004

This has got way off topic probably by me.

To answer your original question NO.

You do not need WASS

as referering to the defanitions of accuracy I was just making a point that I have some idea of the meaning.

What is the Standard Kerry?

I do not know and am proud to admit it.

1.1k · February 1, 2004

GPS SPS Global average positioning domain average is < 13 metres @ 95% horizontal and < 22 metres vertically.

WAAS was designed for 7 metres @ 99% and hence is about 5 metres 95% and 3 metres CEP. Most of the real time monitoring that is done for WAAS purposes is in the vertical as that's the most critical thing that aircraft are concerned with.

As for differential systems, including WAAS, dGPS etc it's the integrity and error monitoring of the position that is more important than straight/pure accuracy.

As far as geoid models are concerned they are simply models that define the interpolated separation distance (~vertical) between GPS ellipsoid heights and orthometric (sea level) type heights. They have absolutely nothing to do with determining initial GPS type coordinates XY or Z.

Cheers, Kerry.

Edited February 1, 2004 by Kerry.

February 1, 2004

Reading some of the posts here gives me a headache. I can only rely on what I have observed with my basic yellow and my friend's Vista, down here in south Florida.

Most times, I can observe no discernable difference. Sometimes, his GPS sends him way off the mark and sometimes mine does. As long as my little yellow takes me where I need to 95% of the time, I'm happy.

February 1, 2004

Boy oh boy, I am kind of sorry I asked the first question. However, because I usually don't learn as fast as maybe I should, I have two more questions for the distinguished panel

1.) What are you guys smoking?

2.) Are you sharing?

Just trying to lighten up the thread a bit, but then maybe its my medications kicking in.

Thumper

PS it has been an education even though some (read most) of it is over my head...................waaaaaay over my head. :mad: :mad:

Edited February 1, 2004 by OKThumper

February 2, 2004

i have a magellan 320 (no waas) my partner has a 330 (waas). we use them for surveying antenna sites for cell and microwave antennas. occassionlly we do surveys together and have never seen a difference in readings from the two units. every time they came up with identical coords.

also, my magellan has gotten me to within 5' of posted coords from this site and also from coords from wireless sites.

non-scientific, but i don't see where waas is any great advantage right now.

4.4k · February 2, 2004

1.Um

2.Huh

Thanks Kerry.

I know explaining things can get quite complicated some times.

As for obsevational purpose.(Benchmark in my front yard)

If I take a reading(A),or make a waypoint(A),and the GPS unit guides me right back to it,

and set there to average,it flucuates from 0' to 3.5'.

Now the BM is my control and Alpha Point of the Geoid.

The Baseline is 1/2 the distance of the Township and 1/2 the width of the Township.(B eta,C eta)= Delta.

I can then tape off 100,200,333,400,666,999, to 1320'and so on.

Now I take my GPS and make A a GO TO,and then to the measured points.

Epsilon

So far 99% of the time it gives me the correct distance to point A.

So then any given point in the Geoid,or Triangle can be calculated from this 3 point problem.

The GPS also uses your initial point,when you 1st initialize it to calculate your position on the Earth,If this BM was my Initialization Point and the control that I am using,then the Satts are still using that same position. And I reference the work to it, all the marks are within 0' to 3.5' throughout the Township.

These marks are what I go back and check and recheck and checkm again.

But like I have heard alot of (Who are you)???What are your credintials?

You don't know what you are talking about.

I know well enough........Like has been stated if it will lead you to where you want to go...98% of the Time,who really cares if it is <1'-10' or 50'

February 2, 2004

I just came across a document published by the Colorado Division of Water Resources, concerning accuracies of GPS data. Field testing was conducted by the Division using GPSr that used averaging vs. units that used WAAS. The purpose was to determine whether the division would accept positional data for water well locations derived from GPS as opposed to surveyed from benchmarks. The following was a quote from this article that summarizes their findings.

"Field testing by the Division of Water Resources of inexpensive 'averaging' GPS units has yielded point position data within a few tens of meters of benchmark surveyed positions. A map plotting and review of data can provide "map corrected" averaged GPS data of good (10-20 meter ranges) quality. By comparison a WAAS enabled GPS unit with averaged position information can attain accuracies of 1-3 meters of benchmark locations."

So this government agency did find accurracies that were an order of magnitude greater with the WAAS enabled then without it.

Reference: Article name: "Why Not GPS?" by Chuck Roberts. Contact Glenn Graham at the Colorado Division of Water Resourses, for copies of the article or field test or general info at 303-866-3581 x8270

As far as I know none of this data is available online.

WAAS...do You Really Need It?

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