GPS+GLONASS and WASS+EGNOS?

[+FireBoxRazor]

Oregon 650.

 

Should all those be on when out HIKING? I know a very rough idea of what they do, but does having them all on complicate anything?

 

I have two option.

 

WASS+EGNOS = off or on

 

GPS = on or off

 

GPS + GLONASS = on or off.

 

Can anyone advise me on these please?

[jholly]

WASS + EGNOS = on

 

GPS + GLONASS = on

[+BlackRose67]

I'm at N45 W075 and always have GPS+GLONASS and WAAS/EGNOS enabled.

[+FireBoxRazor]

So if no point having WASS on does it drain extra battery life? and does it mean that the garmin is not taking advantage of it if it makes no difference?

[+Red90]

I've fond having WAAS/EGNOS available makes no difference whatsoever, so have it set to off. GLONASS on the other hand does improve accuracy and acquisition time so I run with it on.

 

Well. You are in the UK.

 

It makes a substantial difference in North America. Normally doubling accuracy.

[alandb]

I haven't really noticed significant improved accuracy with a WAAS lock either, but it does seem like a good WAAS lock helps reduce the drift from changes in the satellite constellation. I haven't really collected any data on this, so it may just be my perception. I have a old DeLorme LT-40 puck that has WAAS. Just for grins, I used to hook this up to my laptop in my living room and let it track that spot in my house for hours on the Street Atlas USA map. It seemed to me that when I had a good WAAS lock, the 'birdsnest" effect on the track log was a lot "tighter" than without a WAAS lock.

 

My GPS device does not have GLONASS. My tablet does, but I have not done enough GPS navigation with it to make a conclusion on whether GLOSNASS helps or not.

Edited September 10, 2015 by alandb

[Pacific NW]

Here in the Pacific Northwest, WAAS doesn't seem to offer much benefit. On the other hand, enabling GLONASS has brought EPE "accuracy" down to 9 ft. indoors. Pretty impressive in the northern latitudes.

 

Link to a real-time FAA map showing GPS satellite locations: http://www.nstb.tc.faa.gov/RT_WaasSatelliteStatus.htm

 

Also, here's a real-time map that shows GPS satellites, and you can show/hide the various types: https://in-the-sky.org/satmap.php

Edited September 10, 2015 by Pacific NW

[jholly]

Here in the Pacific Northwest, WAAS doesn't seem to offer much benefit. On the other hand, enabling GLONASS has brought EPE "accuracy" down to 9 ft. indoors. Pretty impressive in the northern latitudes.

When I get a WAAS lock I don't notice a large difference, perhaps a couple feet EPE. I do notice better under tree cover performance with GLONASS. I have seen EPE's down to six feet with GLONASS on and in the open. Although WAAS does seem to offer much, I see no reason to turn it off. Now when the newer satellites get operational with two civilian signals and the consumer hardware to match, I expect we will some really great performance.

[+BAMBOOZLE]

I've tried and my units perform better with WAAS turned off.....I don't have GLONASS on the 62S units.

[+fizzymagic]

I've tried and my units perform better with WAAS turned off.....I don't have GLONASS on the 62S units.

 

It is quite literally impossible for that to happen. I know that you believe that is what you saw; there is a word for it: apophenia. But it didn't actually happen that way.

[+ecanderson]

Yep, I guess in the US flatlands you'll get a lock with no issue :}

No matter where you live in the UK, Sussamb, you're the flatlander in relative terms! Offhand, I'd be comfortable saying that 80%+ of my finds are at more than a mile high.

 

Anyway, even when one further west is shadowed by the mountains, we still have access to more easterly WAAS, so a WAAS lock here is worth its weight in geocoins.

Edited September 11, 2015 by ecanderson

[+BAMBOOZLE]

I've tried and my units perform better with WAAS turned off.....I don't have GLONASS on the 62S units.

 

It is quite literally impossible for that to happen. I know that you believe that is what you saw; there is a word for it: apophenia. But it didn't actually happen that way.

 

I had to look up that word ....could be. Its not huge but with all three 62S units performance is better off with WAAS off unless I have a clear view of the horizon. My take is that with WAAS on, two of your 12 sats are trying to lock in to WAAS sat's so the unit searches and searches trying to lock and give you the " little D's ". The majority of the time I can't get a lock so I think I'm better off allowing those two allocated to WAAS to pick up traditional sat's.

[+fizzymagic]

I had to look up that word ....could be. Its not huge but with all three 62S units performance is better off with WAAS off unless I have a clear view of the horizon. My take is that with WAAS on, two of your 12 sats are trying to lock in to WAAS sat's so the unit searches and searches trying to lock and give you the " little D's ".

 

That's not how units or WAAS satellites work. Channels are not dedicated to individual satellites. If the GPS can't get a good signal of a particular satellite on a channel, it uses it for another. At most one channel would be used by the WAAS satellite, and it transmits GPS information like the other GPS satellites in addition to the WAAS data. Garmin engineers are really quite competent, you know.

 

In other words, I suspect that you were predisposed to not like WAAS (a sentiment that is puzzlingly common, I have found) and noticed when you saw evidence that supported your prior conclusion.

[+BAMBOOZLE]

I had to look up that word ....could be. Its not huge but with all three 62S units performance is better off with WAAS off unless I have a clear view of the horizon. My take is that with WAAS on, two of your 12 sats are trying to lock in to WAAS sat's so the unit searches and searches trying to lock and give you the " little D's ".

 

That's not how units or WAAS satellites work. Channels are not dedicated to individual satellites. If the GPS can't get a good signal of a particular satellite on a channel, it uses it for another. At most one channel would be used by the WAAS satellite, and it transmits GPS information like the other GPS satellites in addition to the WAAS data. Garmin engineers are really quite competent, you know.

 

In other words, I suspect that you were predisposed to not like WAAS (a sentiment that is puzzlingly common, I have found) and noticed when you saw evidence that supported your prior conclusion.

 

Actually I was all for it and all my units had it enabled for quite some time.Then I noticed the units weren't behaving as well as they used to and reading the forums I saw others who had experienced problems so I turned off WAAS and the units began to respond better.

My wife and I cache side by side with identical units so I'll do a test and see.

[+ecanderson]

My wife and I cache side by side with identical units so I'll do a test and see.

No, you don't, but it's still a good test all the same. Between my caching buddy and I, we have 3 Oregon 450's, and the two we regularly take out to do a caching run sometimes act like they're from different planets. Both are running exactly the same GPS and Garmin firmware versions, and when this occurs, we are careful to orient them identically and avoid any body 'shielding' differences. Heck, we can lay them on the same rock a couple of feet apart and watch them point 12 feet in opposite directions. These devices do have component tolerances and the like that seem to have a real impact on both claimed position and claimed EPE.

 

So don't put TOO much stock in the results, but tell us what you see. Recommendation ... alternate which of your two units is set up for WAAS several times to see what happens.

 

The correction data provided by both the WAAS and EGNOS systems are designed to provide 'local' offsets to correct for certain types of errors in obtaining an accurate fix. Theoretically, the closer you are to one of their 38 ground stations (WRS), the closer the correction will be to the necessary offset for your particular location, though the interpolation used for predicting errors between ground station positions works really well. I happen to live practically on top of one of them since one of the 22 regional ARTC sites is here as well, and they've set up a ground station on site.

[+BAMBOOZLE]

My wife and I cache side by side with identical units so I'll do a test and see.

No, you don't, but it's still a good test all the same. Between my caching buddy and I, we have 3 Oregon 450's, and the two we regularly take out to do a caching run sometimes act like they're from different planets. Both are running exactly the same GPS and Garmin firmware versions, and when this occurs, we are careful to orient them identically and avoid any body 'shielding' differences. Heck, we can lay them on the same rock a couple of feet apart and watch them point 12 feet in opposite directions. These devices do have component tolerances and the like that seem to have a real impact on both claimed position and claimed EPE.

 

So don't put TOO much stock in the results, but tell us what you see. Recommendation ... alternate which of your two units is set up for WAAS several times to see what happens.

 

The correction data provided by both the WAAS and EGNOS systems are designed to provide 'local' offsets to correct for certain types of errors in obtaining an accurate fix. Theoretically, the closer you are to one of their 38 ground stations (WRS), the closer the correction will be to the necessary offset for your particular location, though the interpolation used for predicting errors between ground station positions works really well. I happen to live practically on top of one of them since one of the 22 regional ARTC sites is here as well, and they've set up a ground station on site.

 

You and fizzy are definitely the technical ones.....all I know is what I read here ( I save about everything ) and what I get " hands on " in the field. You are correct in identical units at times behaving differently but the performance of quality units can be impressive. I assisted in putting out a PT once and carried two units to where I hung each cache, a 60 CSx and Magellan Platinum....the idea was to average the readings of the two. On 120 caches there wasn't much to average...usually either the N or W would be identical, many times both , but on occasion there would be a VERY slight diff. on N or W sometimes not enough to average so I had to pick one.

Somewhere just off the interstate between Denver and Cheyenne is a great test station high up on a rock with clear view of the sky....most of my units were dead on with the rest just a digit off.

Let me just say good units can get you spoiled.

A few observations :

1. Some days seem worse for GPS than others...don't know why but foul weather seems to affect them.

2. In an area west of Henderson , TN going toward Brevard NONE of my Platinums ( 4 ) would get a signal....perfect day and had cached the area with no problems a few times in the past with the same units....it wasn't just one spot , I tried them all day as we drove west ( we cached with a 60 CSx and Oregon 450 which have higher sensitivity than the Platinums but still they always worked before ).

3.Firmware WILL make a unit perform badly....before upgrades we wanted to throw the 450 and 62S in the lake.

4. Folks saying all your unit should do is get you within 20-30 feet....that hasn't been my experience.

With folks hiding micro's down here in the swamp I wouldn't find very many....I'm amazed when at GZ how many I step on or hit my head on.

Thanks to the technical folks who contribute here, I love this stuff and do print outs and bookmarks etc. If Robert contributes much more I will need to give him his own bookshelf. I read so much here that its hard to buy new units....too much information causes paralysis, I'm usually at least one model behind the game but thats all right because in takes almost 2 years to get the bugs out.

[+cheech gang]

There seem to be a couple knowledgeable people here. I am not one of them.

 

To the OP question. Is are there any pros or cons to turning on the waas option in addition to glonass? Or is this answer really "it depends"?

[+ecanderson]

There seem to be a couple knowledgeable people here. I am not one of them.

 

To the OP question. Is are there any pros or cons to turning on the waas option in addition to glonass? Or is this answer really "it depends"?

UNLESS there is something seriously wrong with the firmware of a device, the addition of the correction information provided by WAAS or EGNOS systems can only IMPROVE the quality of the fix. That's precisely why the U.S. and Europe spent a lot of bucks/Euros setting up these systems for their respective aviation industries.

[+ecanderson]

1. Some days seem worse for GPS than others...don't know why but foul weather seems to affect them.

Absolutely true that some days will provide more accurate positioning than others. To start with, the configuration of the satellite constellation varies all the time. While predictable, it might as well be random as far as a cacher is concerned. The quality of what is essentially a mathematical triangulation of your position is impacted by the number of satellites your unit is receiving AND their position in the sky. It would be great if they would all cooperate and form a nice ring around your position at about 60 degrees in the sky, but that just ain't gonna happen. Instead, they sometimes get clustered more overhead or there are gaps in one direction or another. It's actually possible to predict when these situations will occur for a particular location on the earth. We call them 'lousy DOP moments', but they can last for a good bit longer than a 'moment'. I've seen situations where a couple of hours are kinda junky.

 

"DOP" stands for 'Dilution of Precision', and the axis we all worry over is horizontal (not up and down), so when the accuracy of our position readings aren't as good as normal due to any of several variable conditions, what we're seeing are the effects of 'HDOP' (horizontal dilution of precision).

 

Yes, weather can impact things a bit. Any signal attenuation is a bad thing since it can remove from the equation (bad pun) the more marginal satellites that might have been helpful additions. It's the same with being under anything from light to heavy tree canopy. Water does absorb energy in this spectrum. While it gets worse at higher frequencies (which is why your microwave oven reheats your coffee), there's a definite impact on signals in the GPS band as well. Then there's activity in various atmospheric layers between the satellites and us. That's another thing for which WAAS tries to provide correction data since they, like us, are ground based stations. Certain solar events can really ruin a good cache day. They're not common, but they do occur.

 

Suffice it to say that there are times when the quality of the signal being received even when all other conditions are as identical as possible.

 

2. In an area west of Henderson , TN going toward Brevard NONE of my Platinums ( 4 ) would get a signal....perfect day and had cached the area with no problems a few times in the past with the same units....it wasn't just one spot , I tried them all day as we drove west ( we cached with a 60 CSx and Oregon 450 which have higher sensitivity than the Platinums but still they always worked before ).

You talking about the Meridian 'Platinum'? I haven't followed their technology, so have no idea whose chip they were using back then, nor what the claimed/actual sensitivity was for those devices. Would need to know a great deal more about the specifics of that day. These days, if four devices are all dark at once on the highway, it's usually a truck running a jammer, but you're saying it was over a wide area and time. Heck, you might have been out on a day where the sunspots were fouling things up badly.

 

3.Firmware WILL make a unit perform badly....before upgrades we wanted to throw the 450 and 62S in the lake.

True enough, although the reasons why vary. For your Garmin units, there is separate firmware for the GPS receiver and separate firmware for the device. The GPS firmware comes from the chip manufacturer, and is their best shot at providing location information. How they choose to massage that data before handing it off to Garmin's own firmware is always a mystery to anyone outside of the program, and how Garmin chooses to massage that data after it is received from the GPS chip is not provided to us, either. Suffice it to say that what we're seeing on our screens isn't a 'clean' pass-through of the hard mathematical calculations performed on the timing of the signals from the satellites. You probably wouldn't be very happy if it was since it would be pretty jumpy.

 

4. Folks saying all your unit should do is get you within 20-30 feet....that hasn't been my experience.

Nor mine when the stars -- er -- satellites -- are all in perfect divine alignment. I think what folks are saying is that you shouldn't EXPECT to get closer than 20 to 30 feet for a whole host of reasons. When you do, do your happy dance, because there are a lot of reasons that you might not.

 

Let's start out by eliminating the error that occurred when the cache was placed. Whether you can stand on a cache at the posted coordinates using the best technology available (not something you would carry around to cache!) will of course be a function of whether the coordinates provide by the CO were right to begin with, and there's many reasons to suspect that those coordinates will not have been accurate down to the precision of the reading on your device (0.001 minutes). So again, let's ignore that for the moment, critical as it is to the end results when finding a cache... What we want to stick to for the moment is whether your own unit can take you to a theoretical set of coordinates in a repeatable fashion, or rather, how close it can be expected to get you to that position on a repeatable basis.

 

Starting with one obvious mathematical fact, if your device had a perfect knowledge of your WGS84 location, it displays those results to 0.001 minutes. 0.001 minutes represents about 6 feet in the N/S direction, and at my latitude, about 4 feet in the E/W direction. Since the distance between longitude lines shrinks as you get farther from the equator, that E/W number varies depending upon where you are. At the equator, it's more on the order of the 6 feet that you get N/S. Take that into account and then use your own unit(s) to perform the following experiment:

 

We'll use your front yard or whatever other spot you choose, but try to make it a typical 'open sky' location without lots of structures and trees nearby. Take a unit and give it a chance to acquire a decent lock in your 'front yard'. Set it up to record a track and lay it down in the grass and leave it be for 30 minutes. Go back and shut down the track and bring it in and copy that track data to your PC. Look at where the device thought that it was. You'll find that the recorded position moved over time, and for every 0.001 N/S difference, it's giving you 6 feet of offset, and something on the order of 4 feet for every 0.001 E/W. I think you'll be surprised at what you find.

 

Now, let's compound the problem. ANYTHING that degrades the signal quality is going to cause more drift than you experienced in your ideal spot.

1) Nearby structures that can reflect a GPS signal are lethal due to multipath -- the same signal being seen by your unit from more than one path due to the reflected signals.

2) Water, be it in the atmosphere or in the leaves of trees don't do your signal strength any good. That will increase the error.

3) A lousy DOP moment (explained above) where the satellites are in a less than optimal configuration in the sky gives you less ability to triangulate well.

4) Self-induced lousy DOP -- where the way you are carrying the device is causing your body (lots of water) to shield the device from satellite signals coming from the other side of your body (can be much more impactful than you can imagine)

5) Terrain induced lousy DOP -- where the hillside you're standing next to is blocking the signals of satellites, perhaps even half the sky.

 

Anyway, repeat the yard/drift/track experiment above at different times on a couple of different days, and realize the importance of each 0.001 difference at any given moment as I explained. Life will never get any better than that, and you must add to that any of the items 1-5 above when you are out in the 'real world'.

 

Now, add the error of the CO to all of that. Heaven knows what the DOP conditions were, whether the CO measured on multiple days/times, or understood the advantage of using his device's averaging algorithm on any of the trips that actually were made to get coordinates.

 

Now you see why you shouldn't EXPECT to see near-perfect results.

[jholly]

UNLESS there is something seriously wrong with the firmware of a device, the addition of the correction information provided by WAAS or EGNOS systems can only IMPROVE the quality of the fix. That's precisely why the U.S. and Europe spent a lot of bucks/Euros setting up these systems for their respective aviation industries.

 

Well this makes two assumptions.

 

One is you can actually get a WAAS/EGNOS lock. As I've previously mentioned where I cache/hike that's often not the case.

 

Two, that the difference is actually discernible and useful. Tests I've done when I was able to get a good WAAS/EGNOS lock for most of the day showed nothing better than what I normally get with just GPS + GLONASS. By 'better' I mean by observing my position on the screen and using it to navigate. Now, there was an indication on my GPS that accuracy was better, but that's just a number on a screen. If those things turn you on then so be it, but what matters to me is whether my GPS shows my position more accurately. It never did.

 

The real clue is, as ECANDERSON states, that this was set up for the aviation industry and I don't hike/cache up in the air

The point is it was set up to compensate for the effects of the ionosphere. Those effects are just as real on the ground as they are in the air. But actually I was under the impression that WAAS was more for the landing phase of the flight, not so much as the straight and level phase.

[+BAMBOOZLE]

1. Some days seem worse for GPS than others...don't know why but foul weather seems to affect them.

Absolutely true that some days will provide more accurate positioning than others. To start with, the configuration of the satellite constellation varies all the time. While predictable, it might as well be random as far as a cacher is concerned. The quality of what is essentially a mathematical triangulation of your position is impacted by the number of satellites your unit is receiving AND their position in the sky. It would be great if they would all cooperate and form a nice ring around your position at about 60 degrees in the sky, but that just ain't gonna happen. Instead, they sometimes get clustered more overhead or there are gaps in one direction or another. It's actually possible to predict when these situations will occur for a particular location on the earth. We call them 'lousy DOP moments', but they can last for a good bit longer than a 'moment'. I've seen situations where a couple of hours are kinda junky.

 

"DOP" stands for 'Dilution of Precision', and the axis we all worry over is horizontal (not up and down), so when the accuracy of our position readings aren't as good as normal due to any of several variable conditions, what we're seeing are the effects of 'HDOP' (horizontal dilution of precision).

 

Yes, weather can impact things a bit. Any signal attenuation is a bad thing since it can remove from the equation (bad pun) the more marginal satellites that might have been helpful additions. It's the same with being under anything from light to heavy tree canopy. Water does absorb energy in this spectrum. While it gets worse at higher frequencies (which is why your microwave oven reheats your coffee), there's a definite impact on signals in the GPS band as well. Then there's activity in various atmospheric layers between the satellites and us. That's another thing for which WAAS tries to provide correction data since they, like us, are ground based stations. Certain solar events can really ruin a good cache day. They're not common, but they do occur.

 

Suffice it to say that there are times when the quality of the signal being received even when all other conditions are as identical as possible.

 

2. In an area west of Henderson , TN going toward Brevard NONE of my Platinums ( 4 ) would get a signal....perfect day and had cached the area with no problems a few times in the past with the same units....it wasn't just one spot , I tried them all day as we drove west ( we cached with a 60 CSx and Oregon 450 which have higher sensitivity than the Platinums but still they always worked before ).

You talking about the Meridian 'Platinum'? I haven't followed their technology, so have no idea whose chip they were using back then, nor what the claimed/actual sensitivity was for those devices. Would need to know a great deal more about the specifics of that day. These days, if four devices are all dark at once on the highway, it's usually a truck running a jammer, but you're saying it was over a wide area and time. Heck, you might have been out on a day where the sunspots were fouling things up badly.

 

3.Firmware WILL make a unit perform badly....before upgrades we wanted to throw the 450 and 62S in the lake.

True enough, although the reasons why vary. For your Garmin units, there is separate firmware for the GPS receiver and separate firmware for the device. The GPS firmware comes from the chip manufacturer, and is their best shot at providing location information. How they choose to massage that data before handing it off to Garmin's own firmware is always a mystery to anyone outside of the program, and how Garmin chooses to massage that data after it is received from the GPS chip is not provided to us, either. Suffice it to say that what we're seeing on our screens isn't a 'clean' pass-through of the hard mathematical calculations performed on the timing of the signals from the satellites. You probably wouldn't be very happy if it was since it would be pretty jumpy.

 

4. Folks saying all your unit should do is get you within 20-30 feet....that hasn't been my experience.

Nor mine when the stars -- er -- satellites -- are all in perfect divine alignment. I think what folks are saying is that you shouldn't EXPECT to get closer than 20 to 30 feet for a whole host of reasons. When you do, do your happy dance, because there are a lot of reasons that you might not.

 

Let's start out by eliminating the error that occurred when the cache was placed. Whether you can stand on a cache at the posted coordinates using the best technology available (not something you would carry around to cache!) will of course be a function of whether the coordinates provide by the CO were right to begin with, and there's many reasons to suspect that those coordinates will not have been accurate down to the precision of the reading on your device (0.001 minutes). So again, let's ignore that for the moment, critical as it is to the end results when finding a cache... What we want to stick to for the moment is whether your own unit can take you to a theoretical set of coordinates in a repeatable fashion, or rather, how close it can be expected to get you to that position on a repeatable basis.

 

Starting with one obvious mathematical fact, if your device had a perfect knowledge of your WGS84 location, it displays those results to 0.001 minutes. 0.001 minutes represents about 6 feet in the N/S direction, and at my latitude, about 4 feet in the E/W direction. Since the distance between longitude lines shrinks as you get farther from the equator, that E/W number varies depending upon where you are. At the equator, it's more on the order of the 6 feet that you get N/S. Take that into account and then use your own unit(s) to perform the following experiment:

 

We'll use your front yard or whatever other spot you choose, but try to make it a typical 'open sky' location without lots of structures and trees nearby. Take a unit and give it a chance to acquire a decent lock in your 'front yard'. Set it up to record a track and lay it down in the grass and leave it be for 30 minutes. Go back and shut down the track and bring it in and copy that track data to your PC. Look at where the device thought that it was. You'll find that the recorded position moved over time, and for every 0.001 N/S difference, it's giving you 6 feet of offset, and something on the order of 4 feet for every 0.001 E/W. I think you'll be surprised at what you find.

 

Now, let's compound the problem. ANYTHING that degrades the signal quality is going to cause more drift than you experienced in your ideal spot.

1) Nearby structures that can reflect a GPS signal are lethal due to multipath -- the same signal being seen by your unit from more than one path due to the reflected signals.

2) Water, be it in the atmosphere or in the leaves of trees don't do your signal strength any good. That will increase the error.

3) A lousy DOP moment (explained above) where the satellites are in a less than optimal configuration in the sky gives you less ability to triangulate well.

4) Self-induced lousy DOP -- where the way you are carrying the device is causing your body (lots of water) to shield the device from satellite signals coming from the other side of your body (can be much more impactful than you can imagine)

5) Terrain induced lousy DOP -- where the hillside you're standing next to is blocking the signals of satellites, perhaps even half the sky.

 

Anyway, repeat the yard/drift/track experiment above at different times on a couple of different days, and realize the importance of each 0.001 difference at any given moment as I explained. Life will never get any better than that, and you must add to that any of the items 1-5 above when you are out in the 'real world'.

 

Now, add the error of the CO to all of that. Heaven knows what the DOP conditions were, whether the CO measured on multiple days/times, or understood the advantage of using his device's averaging algorithm on any of the trips that actually were made to get coordinates.

 

Now you see why you shouldn't EXPECT to see near-perfect results.

 

Good stuff....yet another I'll have to save.

Two questions :

1. If you can't get a WAAS lock are you better off ( unit accuracy and response ) disabling it or not ?

2. In 1. above will the unit use extra power or be affected in any other way while it is futilely trying to lock on WAAS sats ?

[+ecanderson]

Well this makes two assumptions.

 

One is you can actually get a WAAS/EGNOS lock. As I've previously mentioned where I cache/hike that's often not the case.

I didn't assume you could get a WAAS/EGNOS lock. I simply stated that when it's available, it is specifically set up to improve accuracy, and that's what it does. Assumption 1 = nil.

 

Two, that the difference is actually discernible and useful.

If it's not, you're either in perfect ionospheric conditions or your unit is defective. The results are both discernable and useful. Do you REALLY think they spent all that money to add a correction factor that couldn't be useful? See next assumption (which would actually be #3). WAAS/EGNOS, while not used to actually land an aircraft on autopilot, was developed to a point where one could actually do so. That's its purpose, which I might point out is very near ground level.

The real clue is, as ECANDERSON states, that this was set up for the aviation industry and I don't hike/cache up in the air

I hope that smiley was a 'just joking one', because if it's not, it's just silly. WAAS/EGNOS wasn't set up for IN FLIGHT NAVIGATION. It was designed to be used when aircraft are in proximity to the ground on approach. So BZZZZT to that assumption, too.

 

Look, I know you like to argue interminably about things -- just go read up on the topic. You'll then understand the one and only statement I have made about WAAS/EGNOS -- It will only hurt you if you have defective hardware/software. In any other instance, it can only help.

[+ecanderson]

The point is it was set up to compensate for the effects of the ionosphere. Those effects are just as real on the ground as they are in the air. But actually I was under the impression that WAAS was more for the landing phase of the flight, not so much as the straight and level phase.

Spot on, jholly.

[+ecanderson]

Good stuff....yet another I'll have to save.

Two questions :

1. If you can't get a WAAS lock are you better off ( unit accuracy and response ) disabling it or not ?

2. In 1. above will the unit use extra power or be affected in any other way while it is futilely trying to lock on WAAS sats ?

 

1. If you don't have a WAAS/EGNOS lock, the result is nil. There is simply no correction data to use as offset information to the 'pure' GPS information. No different than having the feature turned off.

2. Not with today's chips, no. It's no different than the device constantly scanning the constellation for any other fringe satellite out on the horizon - which it does all the time.

 

I think the confusion was back eons ago when WAAS was first introduced to consumer gear and being treated as a special case, rather than being fully integrated into the GPS hardware and firmware.

[+Atlas Cached]

Absolutely true that some days will provide more accurate positioning than others. To start with, the configuration of the satellite constellation varies all the time. While predictable, it might as well be random as far as a cacher is concerned.

 

Doesn't have to be

 

If you visit CalSKY and select the 'GPS/GLONASS' link under the 'Satellites' tab, you can enter any date and time, choose your desired interval and duration, click 'go!' and be presented with a chart of the best and worst times for GPS satellite coverage for your chosen location. You can even select the desired minimum elevation (above the horizon) for satellites to be considered in the chart.

[39_Steps]

And don't forget cabin pressure! I average about one airliner flight every 5 years or so, but did have my PN-60 along on the last flight from Texas to California two months ago. I did manage to finally get a signal through the window and track the western portion of the flight across Arizona, Nevada, and California.

 

Track points are about 710 feet apart at one second intervals at altitudes above 36,000 feet in one section. Then I started messing with the built in pressure sensor display, and got it into a mode that only displayed and recorded cabin pressure of 6700 feet through some 10,000+ foot mountains in Yosemite National Park. I did obey the Captain and turned off my gps 50 miles short of the runway and let him land it on his own.

[+ecanderson]

As for some of your other inaccurate statements:

 

My hardware works perfectly thank you, always has done.

I never suggested your particular hardware was broken, only that it would have to be for enabling this feature to degrade your performance. Then enabling WAAS/EGNOS won't hurt you. It might not help, either, as I've said several times before. There was nothing inaccurate about that statement.

 

Garmin didn't spend a fortune developing WAAS/EGNOS (which you seemed to imply, if you didn't mean to do so then I apologise in advance as often your comments are ambiguous), it was spent by others for, as already agreed by you, the aviation industry.

No idea how you interpreted my ramblings to imply that Garmin developed it. Enough of that tangent.

Here even minor differences in position at the speeds aircraft move translate into major positional errors quite quickly. At the speeds you and I move that simply doesn't apply.

Baloney. Speed has nothing to do with this. The error, and the correction for it provided by the WAAS and EGNOS systems, don't change quickly. The resulting corrections are equally applicable at 120mph or 0 mph. You SURE you've read up on this?

[+fizzymagic]

I can assure you I'm well read on this topic.

 

I'm sorry, but I don't believe you. If you had read up on it, you would not post nonsense like this:

 

...it was spent by others for, as already agreed by you, the aviation industry. Here even minor differences in position at the speeds aircraft move translate into major positional errors quite quickly. At the speeds you and I move that simply doesn't apply.

 

Speed has exactly zero to do with it.

[+cheech gang]

Since I will more likely be using the Garmin 64 for geocaching rather than aerospace activities or trying to intercept the "geocache" on the ISS I assume the following to be true:

 

WASS+EGNOS =on

 

GPS + GLONASS = on

 

It may or may not help but it will not hurt.

 

How'm I doin' so far?

[+Atlas Cached]

Since I will more likely be using the Garmin 64 for geocaching rather than aerospace activities or trying to intercept the "geocache" on the ISS I assume the following to be true:

 

WASS+EGNOS =on

 

GPS + GLONASS = on

 

It may or may not help but it will not hurt.

 

How'm I doin' so far?

 

Yes, turn them all on, and go outside and have some fun!

Edited September 14, 2015 by Atlas Cached

[+ecanderson]

Speed has exactly zero to do with it.

Perhaps hearing that again, it will sink in. He certainly didn't understand why I said it. Then again, clearly a non-pilot that doesn't appreciate that it's a vector being used, and why the attempt to insert angular error x speed (which was his point, I think?) is so irrelevant.

[+ecanderson]

How'm I doin' so far?

Perfectly. Even if the entire GLONASS system craps out again the way it did back in the Spring of '14 when their entire constellation of 24 was down for 13 hours, you have the ability to shut that feature down if the unit can't cope with the errors involved for any reason --and then you get what you get with the regular U.S. GPS satellites that are currently available in view. My guess is that given the magnitude of the data errors, even a normal consumer GPS chip would just reject the resulting solutions. The Russians had really screwed the pooch on their ephemeris data and none of their satellites were where they were 'projected' to be in the sky. IIRC, the miss was about an hour and a half of transit time error!

 

Turn it all on and hope for the best.