nincehelser
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Posts posted by nincehelser
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I was not trying to impress any one,
You still have not answered my question.
Here is some more on WASS.
Question? What question?
Oh, and I think we're talking about "WAAS", not "WASS". At least I am.
Can you dig your hole any deeper?
George
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At one point there I was in the Top 10% of the Entire U.S in Mathmatics I think I am still up there somewhere,and I have had several years of Formal Education since then.
That just goes to show..."the top 10% of the Entire U.S. in Mathmatics" is a group of about 30 million people. Wow. Incredibly impressive.
George
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Whatever.....I'm not getting the feeling you really know much about science or engineering, so I'm not going to worry about it.
George
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Ask yourself again. Do you still think rechargeable batteries are expensive? Ask yourself how many trips to the battery store you saved... How much money you saved in gas... How much you saved in batteries... And finally ask yourself... 'What's NOT in my drinking water because of me?'
: )
Nice emotional appeal.
However, a GPS isn't what I'd consider a "high-drain device". It does not even come close to comparing to a digital camera or high-end PDA.
How many trips have I saved to the battery store? I get them at my grocery store, or a lot of other places I happen to be. I think I've only been to a true "battery" store once in my life.
I didn't save anything in gasoline, because I was in there anyway.
As for drinking water...well...if I soaked a bananna peel in a glass of water for a week, I don't think I'd want to drink that, either. I wonder how much gas I've wasted driving to the store to buy banannas?
And what about you folks with dogs and cats. Do I really want *THAT* in my drinking water? I'm sure many geocachers have unwittingly caused more water pollution with their pets than they ever have (or will) with disposable batteries.
Rechargables have their place and application, but they aren't a cure-all for every situation. They certainly aren't going to save the environment.
George
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Sorry. It wasn't necessary for the purposes of this test.
I'll stick with real science and engineering if you don't mind.
George
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There is no *CONTROL POINT*.
Like I said before, this is a comparison between the simulataneous readings of two receivers at the same point.
George
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We used UTM. We then used algebra to determine the distance between the two sets of readings. That math accounts for the decimal point in the distances.
George
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Another thought. If one subscribes to the "Frisbee Rule", a Target or WalMart parking lot would probably be off limits.
If the manager catches you playing Frisbee, or basketball, or skateboarding, they are well within their rights to have you "escorted" off of their property.
George
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It's private property. No doubt about that. It is not "Public Domain", or "Public Property"...unless the city owns the parking lot, but that's usually not the case.
The Targets and Walmarts bought that land, and while they'd like to attract people to visit their stores, they have the final say how their parking lot can is used.
Even if you got their permission, it might start bordering on a "commercial" cache status if they thought is it might attract customers. It's a fuzzy area.
George
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OK. Fixed the spreadsheet.
Average difference between readings: 1.9 meters, or about 6 feet.
Most extreme difference: 3.6 meters, which happened twice, 10% of the time.
They only measured *exactly* the same once, or 5% of the time.
Looking at it another way:
0.0 meter difference: 5%
1.0 meter difference: 15%
1.4 meter difference: 20%
2.0 meter difference: 25%
2.2 meter difference: 20%
2.8 meter difference: 5%
3.6 meter difference: 10%
I still stand by my original conclusion, but obviously the receivers didn't measure exactly the same as often as I originally calculated.
Another way to look at is the receivers were in agreement within 7 feet 85% of the time.
George
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nincehelser: Call me simple if you want but I understood all of your post, and it seems to confirm what most if not all of the math whizes and research guys have said. Which is a GPSr with or without WAAS will work just fine for or hobby/sport. Therefore, if you have a GPSr without WAAS you will be about as likly to be within the "put your GPSr away and use your eyes" range as you would be if it did have WAAS. In addition, you do not need to sell your GPSr and upgrade to one with WAAS, unless you are ready for an upgrade due to the age or useablility of your present GPSr, and just want a GPSr with other goodies and just happens to have WAAS. I better quit now before I confuse myself again, beside here comes the guys with my white jacket and medications.
Thumper
Yes, that's in line with what I'm thinking.
DOH! I just noticed an error in the spreadsheet! Forget what I said. I'm going to have to recalculate.
George
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Do you really leave the charger plugged in all the time, even when not charging batteries?Many rechargers I've seen are drawing power even if they aren't being used...at least the transformers are warm so some energy is being lost.I was referring to rechargers in general. Like for my PDA or electric toothbrush.
I guess you could make a habit of unplugging them all the time when they're not needed, but that's not always practical...especially if you have to move the couch to get to the outlet.
George
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Well, my laptop literally burned up doing the calculations, but I think it had more to do with the fan going out.
Long story short...we took 20 readings at the same, very open location at various times over three days. WAAS and non-WAAS readings had an average difference of 1.6 meters, or roughly 5 feet.
The most extreme difference was 3.6 meters, which happened twice. However, 5 times there was no difference measured at all.
My interpretation is that regular GPS service worked a lot better than I expected. Granted, it's a small sampling, but 25% of the time WAAS and non-WAAS measured the same, 10% of the time they differed by about 11 feet. On average they only differed by 5 feet. That doesn't seem like a huge difference to me, especially for something like hiking or geocaching.
We measured elevation, but I haven't much confidence in that data. I think the Vista's barometer impacted the measurements.
Please realize that we just measured the differences between the readings of a WAAS and non-WAAS receivers. We didn't compare them to a measured point like a benchmark.
George
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Oh, I've decided we've got enough data, at least as far as his science project is concerned. 20 pairs of readings at various times over the last few days. If anyone wants to take a stab at analyzing the raw data, send me an e-mail and I'll send you the Excel spreadsheet.
Thanks
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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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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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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Just curious, how far apart were the two units when you were doing the comparison? I know I read here in the forums that two units held within 3 feet of each other will cause disturbances in the signal (possibly from Kerry or Eraseek?). As for me, I'm still a firm believer in non-WAAS from my own experiments and observations. Even so, a lot of times, my Legend will lead me to within a foot or so of the cache, even under tree cover on cloudy days.
I thought about that. I spaced them consistantly about a foot apart. Hopefully that will quell any interference problem, but maybe not.
I guess a question would be how such interference would tend to manifest itself. My biggest suprise is that the non-WAAS unit seems a lot more accurate than I would have suspected. Maybe it's peaking over at the Vista and cheating?
It's not that I think WAAS is performing poorly, I'm just amazed on how non-WAAS seems to be performing so well.
George
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heres a stupid newbe Q,
whats waas? thanks
TAZ If memory serves, it stands Wide Area Augmentation Service.
It's a system that works over much of North America, and it's intended purpose seems to be to make GPS readings more accurate for aviation use, especially in the elevation readings. It's pretty much standard now in most consumer GPS receivers. The only one that I can think of on the market that doesn't have it is the original yellow eTrex.
There have been debates here regarding the utility of WAAS. My son and I are now doing an experiment to see how WAAS really performs with regards to consumer hand-held units.
So far I'm just getting more confused. Regular GPS seems to be a lot better than I expected, and WAAS seems to be kind of touchy...even out in the open where it should have no problems. It could be the firmware in my Vista is still buggy with regards to WAAS. I'm still trying to figure that one out.
George
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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
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Same here with the "typical" can attain accuracies of 1-3 meters. Especially when inexpensive 'averaging' GPS units actually have some general precision issues displaying less than 3 metres. Again many quote GPS accuracy as X metres but forget the important bit, the type/confidence of those metres.
Here's where I'm getting confused.
Do the Garmins do any kind of position averaging if you just let them sit in one location for a while (like I'm doing in this test)? I was under the impression that they don't, but Magellans do. I'm just trying to figure out why the readings are so close to each other...I just expected the non-WAAS readings to be more spread out than I'm getting.
And the figure the Garmins display ("Ready to navigate to X meters"). Am I correct in thinking this is like a "confidence" reading, or is it really something else?
Elevation is another thing. The Vista seems to vary a lot more than the eTrex yellow. I'm thinking this may have something to do with the Vista's barometer, but any attempts to disable it have met with really strange readings. The between the two units the elevation readings seem to be close most of the time, but the Vista seems prone to wider swings.
Thanks
George
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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
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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.
Did they actually *test* WAAS receivers against non-WAAS?
From the way I read that quote, it sounds like they tested non-WAAS receivers. Their "corrected" data of 10-20 meters doesn't sound too far afield from the typical 15 meters cited. So that part sounds legit.
But the last sentence sounds just like an FYI that WAAS can improve accuracy. It doesn't seem to imply they actually tested WAAS vs non-WAAS receivers to me.
In the test my son and I are currently doing, we're not seeing positioning data more than 3 meters difference between WAAS and non-WAAS. Usually it seems more like 2 meters.
The final results aren't in yet, but the simple yellow eTrex (non-WAAS) seems to be holding its own pretty well against its bigger WAAS-enabled brother (a Vista).
George
TAZ
WAAS...do You Really Need It?
in How do I...?
Posted
>1. What is the scientific use of your test?
Compare the readings of two instruments that calculate their results in different ways.
>2. What is its practical use?
Calibrating instruments comes to mind.
>3. What is it based on?
Observations of measurements taken over time on a single spot.
>4. Where is the RUBBISH?
Your posts, primarily. Just a stream of mathmatical psuedo-babble. You name-drop mathmatical terms, but don't seem to have any clue how they are used. Then you cite definitions for no apparent reason with poorly done links.
The real kicker was when you made a big deal about your being in the to 10% in mathmatics in the USA. I hate to break your bubble, but I'm in the top half of the top 1% as far as math is concerned. That puts me in a group of about 1.5 million people, many of them professional mathemeticians who could easily kick my butt in this area.
So, no. No one was impressed with your 10% play. All it did was make us was put a glaring spotlight on your tenuous grasp on numbers.
I'm sorry if the experiment didn't meet your demanding "standards", but this was set up for a 6-th grader's science fair project, not a doctoral thesis. It met Intel's guidelines for how a display of this sort should be set up and presented.
Case closed. Bye, Bye.
Any further discussion will have to be off-line.
George