Does WAAS improve YOUR gpsr's accuracy?

[+traildad]

I recently pressed clear all on my Meridian gold by accident. Before I knew about the WAAS problem I noticed that it did not seem as accurate. It has been said on another site that the loss of WAAS is of no importance because at worst it will only be 5 feet less accurate. I wish that I could turn WAAS on and off or run two identical GPSr models side by side to see what difference WAAS makes. If someone could run two identical models side by side one with WAAS on and one with WAAS off. Then approach a known waypoint location and note the accuracy of both units. I would love to know if WAAS makes a difference in real world Geocaching. I know it doesn't matter when looking for a road or a building, but finding a cache is not the same. Has anyone done this in the past, can anyone try it now? I would love to know if all this lost WAAS stuff is really just a "no biggie". Thanks Ken

[+KOOLAID105]

I had a Explorist 210 that I broke back in October. When I was getting WAAS signal my accuracy would usually be in the 10-15 foot range with the 210. Sometimes less, sometimes more. I recently got an Explorist 500 that is not getting WAAS and have visited some of the same caches, and noticed that the best accuracy that I can get is about 30 feet. We have found several other caches with the 500 and it does not seem to be a huge problem. I looked forward to having WAAS in the summer as we do alot of summer caching, but since this July 2007 WAAS thing, I most likely won't have it until I wear this 500 out.

 

Honestly, it is nice to have, but I don't think it is a "must-have" feature.

[+jotne]

This will become a 200 post thread.

 

Do a search on WAAS/Egnos and you will find lots of thread about WAAS

[+EScout]

The way to do this is find a super-accurate benchmark and compare with WAAS and without. I have done this with my Meridian Green several years ago. Enter the coordinates of the BM as a waypoint, and stand over it while using the GOTO. (If you want to be more accurate, consider the rounding of the BM to your waypoint coords, and find how many feet N/S or E/W of your rounding and stand over that point, which is within a 3' diameter of the BM.)

I did not do any statistics, but sometimes the WAAS signal was better, sometimes the same, sometimes worse, usually only a few feet difference at most. These benchmarks are in very exposed, good locations, with a good view of the sky and horizons. The displayed distance to the waypoint, while standing over it was almost always better than the reported EPE (accuracy), sometimes much better. Usually after remaining still for a few minutes, the distance shown to waypoint improved by a couple of feet.

Edited March 25, 2008 by EScout

[+traildad]

The way to do this is find a super-accurate benchmark and compare with WAAS and without. I have done this with my Meridian Green several years ago. Enter the coordinates of the BM as a waypoint, and stand over it while using the GOTO. (If you want to be more accurate, consider the rounding of the BM to your waypoint coords, and find how many feet N/S or E/W of your rounding and stand over that point, which is within a 3' diameter of the BM.)

I did not do any statistics, but sometimes the WAAS signal was better, sometimes the same, sometimes worse, usually only a few feet difference at most. These benchmarks are in very exposed, good locations, with a good view of the sky and horizons. The displayed distance to the waypoint, while standing over it was almost always better than the reported EPE (accuracy), sometimes much better. Usually after remaining still for a few minutes, the distance shown to waypoint improved by a couple of feet.

I agree this would be a good way to test it. I just got a second backup Meridian Gold GPSr. If anyone ever comes up with a way to fix the WAAS issue I will try it. One with WAAS on and one with WAAS off and then switch just to be sure. Thanks.

[bigbill25]

This guy did some testing:

 

http://users.erols.com/dlwilson/gpswaas.htm

 

Looks like 95% of the time he was within 3.2 meters using WAAS and 5.3 without it...

 

--Bill

Edited March 25, 2008 by bigbill25

[+Barrettg]

I recently pressed clear all on my Meridian gold by accident. Before I knew about the WAAS problem I noticed that it did not seem as accurate. It has been said on another site that the loss of WAAS is of no importance because at worst it will only be 5 feet less accurate. I wish that I could turn WAAS on and off or run two identical GPSr models side by side to see what difference WAAS makes. If someone could run two identical models side by side one with WAAS on and one with WAAS off. Then approach a known waypoint location and note the accuracy of both units. I would love to know if WAAS makes a difference in real world Geocaching. I know it doesn't matter when looking for a road or a building, but finding a cache is not the same. Has anyone done this in the past, can anyone try it now? I would love to know if all this lost WAAS stuff is really just a "no biggie". Thanks Ken

 

Ken, Here's a very thorough comparison.

 

http://users.erols.com/dlwilson/gpswaas.htm

 

Hope this helps.

 

Gil

[+EScout]

Regarding the Meridians, the problem seems to be if you did a full reset, or did not turn on your GPSr during a certain time period last year. The solution is probably waiting until another change in WAAS satellites and then turn on your Meridian and let it acquire.

 

For your own confidence in the performance of your GPSr, if you are in the USA, go here:

NGS Datasheet by County

Choose state, county, "GPS sites only". Sort by lat or lon, and choose a disk or rod. Other types may not be accessible.

[+Pod-Cache]

I'm located in Nova Scotia, and I've heard from some GPS enthusiasts here that it does not make a big difference in this location or a lot of places in the northeast US since the two WAAS satellites appear on the "horizon", therefore do not improve accuracy dramatically.

[+traildad]

Regarding the Meridians, the problem seems to be if you did a full reset, or did not turn on your GPSr during a certain time period last year. The solution is probably waiting until another change in WAAS satellites and then turn on your Meridian and let it acquire.

 

If there is another change in WAAS satellites won't they broadcast the new info on the current WAAS satellites? I can't get those so how will I get the update?

[dogwalkers2]

I would love to know if WAAS makes a difference in real world Geocaching. I know it doesn't matter when looking for a road or a building, but finding a cache is not the same.

It wouldn't make a bit of difference in the world of geocaching. A geocache's coordinates are only as good as when they are noted when the cache was placed. Even if your GPS had millimetre accuracy, it would still only get you as close as any standard GPS.

 

The only time WAAS would make a difference is if it was used for both placement of the cache and finding of it. In the "world" of GPS, this would require the coordinates of all caches to be corrected...not very likely.

[bigbill25]

I'm located in Nova Scotia, and I've heard from some GPS enthusiasts here that it does not make a big difference in this location or a lot of places in the northeast US since the two WAAS satellites appear on the "horizon", therefore do not improve accuracy dramatically.

That's not quite true. While the WAAS satellite can be used as an additional reference point to compute position, its biggest benefit is to give you local ionospheric delay corrections. These are determined by ground stations, then relayed through the WAAS satellites. In your case, there are ground stations in Maine and Newfoundland, so you should be getting reasonable corrections in Nova Scotia.

 

--Bill

[+Renegade Knight]

It improves my GPSs Estimated Position Error. I've seen it as low as 3' with WAAS enabled. 15 is about the best with it off. I've never actually tried to do a comparison to a known point though.

[+Klemmer]

I have done so many times at adjusted (very accurate) benchmarks, and yes, it certainly does improve your accuracy. Those who say it doesn't are (politely) under-informed.

[+traildad]

I thought of an idea to test the accuracy of my Meridian Gold. I used Google Earth to mark a waypoint in front of my house. I imported it into my GPSr and went outside. When I first acquired satellite lock it said I was 258 feet from the spot. As I stood there the GPSr averaged the reading and the distance slowly came down until it read 3 feet. It took a few minutes, but I was happy with the results.

[cracked cork]

I have done so many times at adjusted (very accurate) benchmarks, and yes, it certainly does improve your accuracy. Those who say it doesn't are (politely) under-informed.

 

This is from my 60CX manual......"Currently enabling WAAS on your GPSMAP 60CX in regions that are not supported by ground stations, may not improve accuracy, even when receiving signals from an SBAS satellite. In fact it can degrade the accuracy to less then that provided by GPS satellites alone. For this reason, when you enable WAAS on your Garmin GPS receiver, the receiver automatically uses the method that achieves the best accuracy".

 

Can someone tell me what they mean by ground stations? I am trying to get a grip on all the terminology.

[+LifeOnEdge!]

I would love to know if WAAS makes a difference in real world Geocaching. I know it doesn't matter when looking for a road or a building, but finding a cache is not the same.

It wouldn't make a bit of difference in the world of geocaching. A geocache's coordinates are only as good as when they are noted when the cache was placed. Even if your GPS had millimetre accuracy, it would still only get you as close as any standard GPS.

 

The only time WAAS would make a difference is if it was used for both placement of the cache and finding of it. In the "world" of GPS, this would require the coordinates of all caches to be corrected...not very likely.

 

This post is a bit confusing/confused. It makes an assumption that just isn't true.

 

While a cacher has almost no control (or information on) the cache owner's conditions while determining the posted coordinates, a cacher does have control over their own conditions. These two errors are independant -- not linked together in any way.

 

Ideally, we would like to believe that a cache's posted coordinates are completely accurate. Since these posted coordinates are only stated to three significant digits in decimal minutes, regardless of the cache owner's accuracy, the actual accuracy depends directly on how close the cache is to the corner of this "grid" (created by those three significant digits.)

 

Add to this the error with or without WAAS by the cache owner.

 

Now add to this the error of your GPS/satellite conditions while you are searching.

 

Realize that these errors are NOT linear. While you may have an idea of the order of these errors, you never know the direction. (Estimated accuracy is a circle, not a line.)

 

The greater your field accuracy is, the less error you're adding to the process. The lesser your field accuracy, the more error you are adding to the process. If WAAS gives you a more accurate reading in the field, the total error will certainly be less.

 

Here is a link that is useful in this discussion: http://gpsinformation.net/waasgps.htm

Edited April 7, 2008 by LifeOnEdge!

[+LifeOnEdge!]

I have done so many times at adjusted (very accurate) benchmarks, and yes, it certainly does improve your accuracy. Those who say it doesn't are (politely) under-informed.

 

Speaking of being under-informed, you guys might also find this information "informative:"

 

http://gpsinformation.net/waasgps.htm

[+EraSeek]

This is the near-real time coverage area for WAAS

http://www.nstb.tc.faa.gov/RT_VerticalProtectionLevel.htm

[+LifeOnEdge!]

This is from my 60CX manual......"Currently enabling WAAS on your GPSMAP 60CX in regions that are not supported by ground stations, may not improve accuracy, even when receiving signals from an SBAS satellite. In fact it can degrade the accuracy to less then that provided by GPS satellites alone. For this reason, when you enable WAAS on your Garmin GPS receiver, the receiver automatically uses the method that achieves the best accuracy".

 

Can someone tell me what they mean by ground stations? I am trying to get a grip on all the terminology.

 

cracked cork, you might find this link of some use:

 

http://en.wikipedia.org/wiki/Differential_GPS

[+EraSeek]

I have done so many times at adjusted (very accurate) benchmarks, and yes, it certainly does improve your accuracy. Those who say it doesn't are (politely) under-informed.

 

Speaking of being under-informed, you guys might also find this information "informative:"

 

http://gpsinformation.net/waasgps.htm

 

Consider the year of that write-up. (revised: 28 July 2002)

WAAS is now fully operational, coverage has expanded, (yes even Canada), there were 2 WAAS sats, then 4, now 2 new ones.

[cracked cork]

[

 

cracked cork, you might find this link of some use:

 

http://en.wikipedia.org/wiki/Differential_GPS

 

Thanks for all of the above links. That is alot of info to digest, or even try to. Unless I have read it wrong, it sounds like its a crap shoot if its going to help the average geocacher, unless all the conditions are perfect. That takes me back to the statement in my manual that "the receiver automatically uses the method that achieves the best accuracy".

[+EraSeek]

name='cracked cork' date='Apr 6 2008, 05:51 PM' post='3410103']

[

 

cracked cork, you might find this link of some use:

 

http://en.wikipedia.org/wiki/Differential_GPS

 

Thanks for all of the above links. That is alot of info to digest, or even try to. Unless I have read it wrong, it sounds like its a crap shoot if its going to help the average geocacher, unless all the conditions are perfect. That takes me back to the statement in my manual that "the receiver automatically uses the method that achieves the best accuracy".

 

Well I'm not sure I would be that pessimistic. Leave it on. The newer units will decide when it can and can't get it. WAAS does improve accuracy, but generally it is not a live or die situation here. WAAS does more than one thing:

 

It corrects for clock and sat position errors so your unit can achieve better accuracy, because it is all about timing and geometry. This is nearly half the errors.

 

It corrects for ionospheric disturbances (sp?). An active ionosphere will delay the signal and therefore corrupt your position. So again, timing. One nanosecond (one-billionth of a second) in delay will cause you one foot of error in position. However, the ionosphere is not always very active or maybe be much more active in one place than another. Generally the further south and the closer to mid-day the more active you will find the ionosphere above you (also during solar storms). At night you have very little correction to be made. This is nearly half of the rest of the errors. It is this portion of WAAS that depends on where you are and your GPS to be part of that solution.

 

Generally, look at it this way. If you have an open view of the sky, at least partially, you should be good to go for WAAS. Clouds and fog and rain are not a problem. If you were on a boat in heavy fog and looking for a buoy it may take you several passes to find that buoy, but with WAAS you will probably nail it the first time.

Edited April 7, 2008 by EraSeek

[+geognerd]

Can someone tell me what they mean by ground stations? I am trying to get a grip on all the terminology.

Explanation of WAAS and reference stations

Map of reference stations and other WAAS components (as of 2007)

[+StarBrand]

Does WAAS help with accuracy of your unit?? - no doubt about it - everything is more accurate when you can get the WAAS corrections.

 

Does WAAS help with Geocaching?? Debatable but probably not much.

[+Red90]

Does WAAS help with Geocaching?? Debatable but probably not much.

 

Actually, I would say yes..... This is more because the placements have become much more accurate since WAAS was availble up here. You see, before the new satellites, it was basically impossible to hold a WAAS lock at our location due to the sat being too low in the sky. Since the new sats were put into service, I've seen a much better accuracy for hides than before.