Gps

[+wcfd661]

IS A WAAS CAPABLE UNIT A MUST IN FINDING THE CACHES? WILL THE OLDER UNITS GET YOU CLOSE ENOUGH TO FIND THEM?

[+Thot]

IS A WAAS CAPABLE UNIT A MUST IN FINDING THE CACHES? 

No.

 

WILL THE OLDER UNITS GET YOU CLOSE ENOUGH TO FIND THEM?

Yes.

 

I believe you get closer with WAAS, and therefore it's easier. Some others disagree with this.

Edited June 14, 2005 by Thot

[+EraSeek]

Certainly not a must.

[+workerofwood]

WAAS *may* put you closer to the coordinates, but you don't know if the hider used it when they placed the cache, so it is no guarantee. They may have had an error of 100' when they marked the coordinates.

[+Team Cotati]

IS A WAAS CAPABLE UNIT A MUST IN FINDING THE CACHES?  WILL THE OLDER UNITS GET YOU CLOSE ENOUGH TO FIND THEM?

It is not a must and Yes, you will get close enough without it. However you'd have to go waaaaaayyyyy out of your way to find a unit on the market that does not support WAAS. Some report that they believe that enabling WAAS drain their batteries much faster. I have yet to see this assertion substantiated. No doubt that every bit of processing in the unit results in some degree of additional power consumption, just how much WAAS affects battery life is, as far as I know, insignificant.

 

As Garmin states it:

"You've heard the term WAAS, seen it on packaging and ads for Garmin® products, and maybe even know it stands for Wide Area Augmentation System. Okay, so what the heck is it? Basically, it's a system of satellites and ground stations that provide GPS signal corrections, giving you even better position accuracy. How much better? Try an average of up to five times better. A WAAS-capable receiver can give you a position accuracy of better than three meters 95 percent of the time. And you don't have to purchase additional receiving equipment or pay service fees to utilize WAAS."

 

"WAAS signal reception is ideal for open land and marine applications. WAAS provides extended coverage both inland and offshore compared to the land-based DGPS (differential GPS) system. Another benefit of WAAS is that it does not require additional receiving equipment, while DGPS does."

 

"Other governments are developing similar satellite-based differential systems. In Asia, it's the Japanese Multi-Functional Satellite Augmentation System (MSAS), while Europe has the Euro Geostationary Navigation Overlay Service (EGNOS). Eventually, GPS users around the world will have access to precise position data using these and other compatible systems."

 

Why you would not use WAAS is a mystery.

 

Cache on Dude!!

Edited June 14, 2005 by Team Cotati

[TCE]

Make sure you can actually pick up the WAAS satelite where you live. Where I live in Oregon, I've never been able to pick it up. It could be that there are too many trees where I live, or the hills are always in the way, no matter where I am...I don't know...but I have a feeling that I may be a tad bit north to find the satelite unless I'm way out in the flat...or on top of a tall hill, or mountain.

 

So, I've never used WAAS to find any geocaches, and have come within a few feet regardless on occasion. We're usually within 20 feet on average...even under heavy tree cover.

 

I hope you find lots of caches

[JadeLuTristan]

Just started geocaching yesterday and found 3 out of the 4 attempted with no GPS unit. Will get one ASAP but will be caching in the mean time.

[+Team Cotati]

Make sure you can actually pick up the WAAS satelite where you live. Where I live in Oregon, I've never been able to pick it up. It could be that there are too many trees where I live, or the hills are always in the way, no matter where I am...I don't know...but I have a feeling that I may be a tad bit north to find the satelite unless I'm way out in the flat...or on top of a tall hill, or mountain.

 

So, I've never used WAAS to find any geocaches, and have come within a few feet regardless on occasion. We're usually within 20 feet on average...even under heavy tree cover.

 

I hope you find lots of caches

The?......It? Those sound like singular terms to me.

 

More from Garmin:

 

"WAAS consists of approximately 25 ground reference stations positioned across the United States that monitor GPS satellite data. Two master stations, located on either coast, collect data from the reference stations and create a GPS correction message. This correction accounts for GPS satellite orbit and clock drift plus signal delays caused by the atmosphere and ionosphere. The corrected differential message is then broadcast through one of two geostationary satellites, or satellites with a fixed position over the equator. The information is compatible with the basic GPS signal structure, which means any WAAS-enabled GPS receiver can read the signal."

[+Prime Suspect]

The?......It? Those sound like singular terms to me.

WAAS was designed for aircraft navigation, not people hiking in the woods. Generally speaking, you're probably only going to be able to get one WAAS satellite, so it's common to refer to it singly.

[+EraSeek]

I live in Washington State. 48 degrees north. It is not uncommon for me to get both (2) WAAS satelliteS. No, when under tree cover don't expect to get them.

 

Wings were designed for birds, so I guess that means people shouldn't be using them to fly airplanes? You don't have to be an aircraft to take advantage of WAAS. You just have to have some exposure to a lower sky view.

[+bigdog999]

Ilive in Massachusetts, most of the caches are in wooded areas. I've decided that I get close enough without WAAS, and since WAAS uses more battery juice, I only enable it when I'm street navigating. One feature I'd like Garmin to include are settings profiles where you can change settings based on various profiles, ie street navigation vs geocaching.

[vagabond]

http://gps.faa.gov/programs/WAAS/howitworks-text.htm

 

Try this, tells you all you want to knoww about WAAS

Edited June 15, 2005 by vagabond

[+Melrose Plant]

Up until a few weeks ago, I never had WAAS capability. Now I do. I messed around with it some. I couldn't tell where it made any difference in my neck of the woods, which would be Central Iowa. I leave it turned off, and haven't had any trouble (well, no more than usual) finding caches.

[+Team Cotati]

Vagabond........thank you.

[+fizzymagic]

WAAS *may* put you closer to the coordinates, but you don't know if the hider used it when they placed the cache, so it is no guarantee. They may have had an error of 100' when they marked the coordinates.

Well, WoW, while what you say may be true for any single individual cache, on average enabling WAAS will cause your GPS to zero out closer to the posted coordinates for the cache.

 

And its use certainly improves the quality of the coordinates one posts for hidden caches!

[+StarBrand]

While it is important to remember that our GPSr can give us coordinates with large errors (60 foot or more) - most of the time (95+%) - the error is aless than 30 feet and with WAAS on and working well that drops to 12 or less. Still lots of room for much error - but WAAS makes it closer. Generally.

 

Not much help though if coords are just plain bad or if the hider had a 60 foot error at placement plus the 30 foot error you are getting......but chances of that are really quite low.

[TCE]

Thanks for the correction! I had no idea there were 2 WAAS satelites! How cool! I hope one of those repeater stations can broadcast to most of Oregon, that would be cool! I'll have to try it out again. I haven't used it in a while.

[+WhatsRNutts]

I have a Garmin GPS 38. it is about 8-9 years old. I have taken it out several time in the past week trying to figure out how to use it. I have it all figured out except that in 20 minutes it not once got any information from the 8 satelites that were showing up on the screen...it just said "acquiring EPE" and nothing else. could it be that it is too old?

[+sbell111]

I have a Garmin GPS 38. it is about 8-9 years old. I have taken it out several time in the past week trying to figure out how to use it. I have it all figured out except that in 20 minutes it not once got any information from the 8 satelites that were showing up on the screen...it just said "acquiring EPE" and nothing else. could it be that it is too old?

Your unit should still work. Check your owner's manual for the proper initialization instructions. If you no longer have your manual, you can download one here. Page 8 has the instructions that you need.

[+sbell111]

I was curious, so I checked ebay for 38s. They actually still sell regularly at prices from 35-80 bucks. One was being advertised as NIB. Another was touted as 'the smallest and easiest to use' unit. I think that some people may fib in their auction descriptions.

[+Kai Team]

WAAS *may* put you closer to the coordinates, but you don't know if the hider used it when they placed the cache, so it is no guarantee. They may have had an error of 100' when they marked the coordinates.

WAAS will *always* put you closer, assuming you can pick up the WAAS signal.

 

If the hider had an error of 100' and you have an error of 35' (without WAAS), your combined error could be as large as 135'. If you use WAAS and have an error of 7', your combined error is no larger than 107'. 107' is still a large error, but smaller than 135'!

[+Kai Team]

Make sure you can actually pick up the WAAS satelite where you live. Where I live in Oregon, I've never been able to pick it up.

Before your unit will use WAAS it has to download the "almanac" for the WAAS satellites, which also allows it to more easily find the appropriate WAAS satellite in the future.

 

Go to a location (e.g. hilltop) with an unobstructed view of the southern horizon. Turn WAAS on and be patient - it may take 10-15 minutes. You'll know it's found WAAS when it locks onto a satellite with a number higher than 34. You'll know it's using WAAS when you see a little "D" in the satellite strengh bar (at least on a Garmin).

 

Once your GPSr has found the WAAS satellite and downloaded the almanac, it will have a much easier time finding it in the future, assuming you're not more than 600 miles from where you initialized it!

 

However, to the OP - WAAS is by no means required to find geocaches!

[+WhatsRNutts]

I have a Garmin GPS 38.  it is about 8-9 years old.  I have taken it out several time in the past week trying to figure out how to use it.  I have it all figured out except that in 20 minutes it not once got any information from the 8 satelites that were showing up on the screen...it just said "acquiring EPE" and nothing else.  could it be that it is too old?

Your unit should still work. Check your owner's manual for the proper initialization instructions. If you no longer have your manual, you can download one here. Page 8 has the instructions that you need.

I have the owners manual and have tried doing everything it says to do step by step... maybe I'm just not getting it... ill try again...thank you!

[+Prime Suspect]

WAAS will *always* put you closer, assuming you can pick up the WAAS signal.

No, not always. A GPS unit will not mix WAAS and non-WAAS data when solving for the location. If you have a lock on 8 satellites, but your GPS has acquired WAAS data on only 4 of them, the GPS will only use those 4 to calculate the position. That could cause you to end up with a much less accuracy than if WASS was turned off, and all 8 satellites were used (particularly if those 4 formed a poor configuration).

[+sbell111]

I have the owners manual and have tried doing everything it says to do step by step... maybe I'm just not getting it... ill try again...thank you!

OK. A little more research turned up this info.

 

The first thing you want to do is put in brand new batteries. You're going to need them.

 

Do NOT do a master reset on this unit. Instead, clear you autolocate info by holding down the page button as you power the unit up.

 

Next, make sure that the unit is in autolocate mode.

 

Place the unit outside where it has the best view of the most sky as possible.

 

Leave it there. It may take an hour (or two) to get a lock. Once you have a lock, leave it out there for as long as possible so it can update ephemeris data from all of the sats.

[+EraSeek]

WAAS will *always* put you closer, assuming you can pick up the WAAS signal.

No, not always. A GPS unit will not mix WAAS and non-WAAS data when solving for the location. If you have a lock on 8 satellites, but your GPS has acquired WAAS data on only 4 of them, the GPS will only use those 4 to calculate the position. That could cause you to end up with a much less accuracy than if WASS was turned off, and all 8 satellites were used (particularly if those 4 formed a poor configuration).

I don't believe this to be correct at all. Some time back Garmin had a patch fixing this problem, so that the best configuration is used as opposed to prioritizing a waas sat that has a less favorable position.

[+EraSeek]

This is all I could find on that: "Improved WAAS/EGNOS satellite selection algorithm to select the satellite with the most beneficial corrections given the unit's current position. "

 

You brought up a good point though, about mixing sats. I'm not sure if this statement covers it or not. I'd like to see some specific link or statement clearing this point up.

[+Kai Team]

I'd like to see some specific link or statement clearing this point up.

I'm also curious. The FAA says:

WAAS provides better accuracy that GPS alone. Non-aviation WAAS receivers in the aviation WAAS coverage area (http://www.nstb.tc.faa.gov/vpl.html) will get far better accuracies due to the WAAS corrections they are receiving.

 

The link shows that aviation coverage is available throughout the continental US, so it's a pretty unequivocal statement.

 

I've emailed Garmin technical support and asked if there are ANY circumstances under which using WAAS on a handheld GPSr will degrade positional accuracy. I'll let you know what they say!

[+Team Cotati]

WAAS will *always* put you closer, assuming you can pick up the WAAS signal.

No, not always. A GPS unit will not mix WAAS and non-WAAS data when solving for the location. If you have a lock on 8 satellites, but your GPS has acquired WAAS data on only 4 of them, the GPS will only use those 4 to calculate the position. That could cause you to end up with a much less accuracy than if WASS was turned off, and all 8 satellites were used (particularly if those 4 formed a poor configuration).

Precious beyond belief.

[+fizzymagic]

WAAS will *always* put you closer, assuming you can pick up the WAAS signal.

No, not always. A GPS unit will not mix WAAS and non-WAAS data when solving for the location.

You stated this incorrectly. What you should have written is:

 

A defective GPS unit will not mix WAAS and non-WAAS data when solving for location.

 

There is no excuse for such behavior in GPS firmware; the primary WAAS correction is ionospheric, which is not given on a per-satellite basis. The ephemeris and clock corrections, which are, are considerably smaller and the GPS can get the position perfectly well without them.

 

One other note: WAAS corrections do not require a current WAAS satellite lock; most WAAS corrections should be good for at least 10 minutes or so after they have been downloaded by the unit.

 

The urban legend that GPS accuracy with WAAS is worse than without does not bear repeating, since it is only applies to significantly defective GPS firmware.

[+Team Cotati]

WAAS will *always* put you closer, assuming you can pick up the WAAS signal.

No, not always. A GPS unit will not mix WAAS and non-WAAS data when solving for the location.

You stated this incorrectly. What you should have written is:

 

A defective GPS unit will not mix WAAS and non-WAAS data when solving for location.

 

There is no excuse for such behavior in GPS firmware; the primary WAAS correction is ionospheric, which is not given on a per-satellite basis. The ephemeris and clock corrections, which are, are considerably smaller and the GPS can get the position perfectly well without them.

 

One other note: WAAS corrections do not require a current WAAS satellite lock; most WAAS corrections should be good for at least 10 minutes or so after they have been downloaded by the unit.

 

The urban legend that GPS accuracy with WAAS is worse than without does not bear repeating, since it is only applies to significantly defective GPS firmware.

"firmware"? Crack me up.

[+Prime Suspect]

This is all I could find on that: "Improved WAAS/EGNOS satellite selection algorithm to select the satellite with the most beneficial corrections given the unit's current position. "

 

You brought up a good point though, about mixing sats. I'm not sure if this statement covers it or not. I'd like to see some specific link or statement clearing this point up.

I don't believe this to be correct at all. Some time back Garmin had a patch fixing this problem, so that the best configuration is used as opposed to prioritizing a waas sat that has a less favorable position.

 

I can't find any patch info that backs this up. The statement you quote only concerns selecting the best satellite to get the correction data from. I do know (straight from a Garmin tech), that they will not intermingle WAAS enhanced data with non-enhanced data to calculate a location.

[+EraSeek]

Here is the flaw in your argument. Lets think about how WAAS works. It is not the individual Sat's themselves which are being adjusted by the WAAS corrections, what is happening is that the WAAS almanac for the corrections are downloaded to THE GPS RECIEVER, it is a grid of corrections, and your reciever applies these corrections according to that grid. It takes a bit of time to gather the almanac and apply the corrections, but the corrections should be made to all the sats, not just some. Thus, though there is some delay in applying the corrections, it should be global, and the comprimising of any position solution should be short. This is probably why when you first lock on to WAAS your EPE will jump way up for a short period before dropping down to an improved EPE. If I am correct this would validate your point about mixing WAAS and Non-WAAS but it would also point out that such a degraded position error due to WAAS would be short lived and WAAS corrections are always a benefit once applyed.

 

"This Iono data (and other corrections) are constantly uploaded to the Geo Sats for re-transmission to GPS navigation receivers. There is no interpolation between ground stations by the receiver. This is because the WAAS master system computes a "grid of Iono corrections" which are location dependent based on the user's position. There is an interpolation/extrapolation process to determine the iono correction, but it is not specifically related to the location of ground stations that collect the information. The Iono-corrections grid offered by WAAS are interpolated and applied by the receiver.

 

GPS receivers must then apply the data for corrections appropriate at their location. This may take five or ten minutes to complete in a typical receiver."

[+EraSeek]

Just a note, clock and sat position errors are are corrected in the almanac updates for each satellite, however the iono error corrections are based on the recievers position and thus the grid.

 

From Dale DePriest's site:

"It seems that Garmin will favor differentially corrected satellites, when at least four exist, to the exclusion of regular satellites. If the four are in a poor geometric relationship the epe number, and possibly the accuracy of the solution, can be worse that it was with a regular solution. Luckily the GEO will generally download corrections for all of the satellites above a mask angle of 5 degrees so this anomaly is usually short lived. "

[+Team Cotati]

Here is the flaw in your argument. Lets think about how WAAS works. It is not the individual Sat's themselves which are being adjusted by the WAAS corrections, what is happening is that the WAAS almanac for the corrections are downloaded to THE GPS RECIEVER, it is a grid of corrections, and your reciever applies these corrections according to that grid. It takes a bit of time to gather the almanac and apply the corrections, but the corrections should be made to all the sats, not just some. Thus, though there is some delay in applying the corrections, it should be global, and the comprimising of any position solution should be short. This is probably why when you first lock on to WAAS your EPE will jump way up for a short period before dropping down to an improved EPE. If I am correct this would validate your point about mixing WAAS and Non-WAAS but it would also point out that such a degraded position error due to WAAS would be short lived and WAAS corrections are always a benefit once applyed.

 

"This Iono data (and other corrections) are constantly uploaded to the Geo Sats for re-transmission to GPS navigation receivers. There is no interpolation between ground stations by the receiver. This is because the WAAS master system computes a "grid of Iono corrections" which are location dependent based on the user's position. There is an interpolation/extrapolation process to determine the iono correction, but it is not specifically related to the location of ground stations that collect the information. The Iono-corrections grid offered by WAAS are interpolated and applied by the receiver.

 

GPS receivers must then apply the data for corrections appropriate at their location. This may take five or ten minutes to complete in a typical receiver."

Who's argument?

[+Glenn]

You are saying the same thing just in different ways.

[+EraSeek]

You are saying the same thing just in different ways.

In some ways, yes, but Prime Suspect's suggestion is that WAAS was made for aviation and thus it is somehow useless for all else, and that using WAAS can actually be worse than not useing WAAS, and this is patently untrue, though technically true for a short period before WAAS is fully applied. It is like saying that cars are useless things because there is a period before you put it into drive when it doesn't "go".

 

WAAS always will improve position once fully applied. This can take anywhere from a few seconds to maybe 5 minutes depending on where the data stream is in it's cycle and how much the almanac in your gps needs to gather.

 

Now the second part of all this is HOW MUCH IMPROVEMENT will you get with WAAS. That depends. If the Ionosphere is active, than it may help alot, If not so active, maybe not much. Generally, for what we do, it is not a huge deal. Generally, it may get you from 20' away down to a few feet away when WAAS is applied.

[+Kai Team]

WAAS *may* put you closer to the coordinates, but you don't know if the hider used it when they placed the cache, so it is no guarantee. They may have had an error of 100' when they marked the coordinates.

WAAS will *always* put you closer, assuming you can pick up the WAAS signal.

 

If the hider had an error of 100' and you have an error of 35' (without WAAS), your combined error could be as large as 135'. If you use WAAS and have an error of 7', your combined error is no larger than 107'. 107' is still a large error, but smaller than 135'!

When I responded to the post from workerofwood (and started the great WAAS debate ), I was actually disagreeing with a more basic point: That WAAS would not help unless the hider also used WAAS when they placed the cache.

 

Still waiting to hear from Garmin on the more technical question raised by Prime Suspect (it is an interesting question)...don't really expect to hear over the weekend.

[+Team Cotati]

I find this 'debate' fascinating.

 

Here we have a group of people who just can't wait to have the most latest, prettiest and just plain swell GPSr technology known to mankind. Presumably this is for the purpose of assisting in hiding and finding stuff that has been specifically hidden so that you will use your GPSr in the process of finding it.

 

Then for reasons perhaps only known by God almighty they are escared all to hellandback to use the single most important component of the technology that will improve the accuracy of their navigation endeavors.

 

No doubt that buried somewhere deep deep deep within the bowels of the library of the American Psychiatric Association, there lies an explaination.

 

Let's not even mention 'rant'.

 

And since you will never know whether or not the hider did or did not use WAAS....?

 

Epilogue:

 

On second thought, since it now appears as though WAAS in fact might be causing GPSr's to actually be less accurate with WAAS enabled, I am considering just turning the freaking thing off. (WAAS that is)

 

Nu Bees, my sincerest aplolgies.

Edited June 18, 2005 by Team Cotati

[+Prime Suspect]

Here is the flaw in your argument. Lets think about how WAAS works. It is not the individual Sat's themselves which are being adjusted by the WAAS corrections, what is happening is that the WAAS almanac for the corrections are downloaded to THE GPS RECIEVER, it is a grid of corrections, and your reciever applies these corrections according to that grid. It takes a bit of time to gather the almanac and apply the corrections, but the corrections should be made to all the sats, not just some. {snip}

That would be true, if that's how the system worked. But it isn't.

 

WAAS data contains corrective information on ionospheric disturbances, timing and satellite orbit errors. While the first will cover a large area, the last two are, obviously, on a satellite by satellite basis. Once you get all the WAAS data for a satellite, it then (and not before) becomes available for use in a WAAS-enabled solution (that's when that satellite's bar shows the WAAS indicator).

 

That's how it's sometimes possible to end up with only a few WAAS enabled birds, and end up with a poorer solution using it, than without it. I'm not saying that happens very often, but it does happen, and that's why the statement that WAAS will always give you better results, is false.

 

I'll end this with a quote from Joe Mehaffey's excellent article on the what's and why's of WAAS:

 

How much improvement in accuracy can I expect when WAAS corrections are working properly?

Answer: This is difficult to say with any certainty. We have observed that MOST OF THE TIME WAAS appears to improve averaged accuracy at a fixed location for maybe 5 minutes averaging from about 7 meters to perhaps 3 meters. Sometimes there has been no improvement and a few times (when WAAS signals were not of good quality or when we were far from a WAAS correction station) the measurements have actually had more error with WAAS than without.

 

The upshot of this is: WAAS is a tool for casual GPS users. It is not guaranteed to work, it is not guaranteed to increase accuracy, it is not really able to tell you when it will improve accuracy, when it will have no effect, or when it will make for less accuracy than the normal GPS signal. Under good conditions when YOU ARE OUT IN THE CLEAR AND RECEIVING A GOOD SIGNAL FROM THE WAAS SATELLITE, you should get both improved accuracy and improved position stability. YOU must insure that you have the proper conditions so as to experience the improvement at YOUR location.

 

This is just the way it is and remember: If you do not like the current limitations of WAAS there is a very simple option -Turn it off.

Edited June 18, 2005 by Prime Suspect

[+WhatsRNutts]

I have the owners manual and have tried doing everything it says to do step by step...  maybe I'm just not getting it... ill try again...thank you!

OK. A little more research turned up this info.

 

The first thing you want to do is put in brand new batteries. You're going to need them.

 

Do NOT do a master reset on this unit. Instead, clear you autolocate info by holding down the page button as you power the unit up.

 

Next, make sure that the unit is in autolocate mode.

 

Place the unit outside where it has the best view of the most sky as possible.

 

Leave it there. It may take an hour (or two) to get a lock. Once you have a lock, leave it out there for as long as possible so it can update ephemeris data from all of the sats.

thank you so much sbell!! I will try this first thing tomorrow morning. I was out doing a fund raiser and then doing like 4 hours of caching. so I am terrible tired and sunburnt. ill replyback tomorrow whether or not it works... thank you again for doing all that research for me.

[+EraSeek]

WAAS data contains corrective information on ionospheric disturbances, timing and satellite orbit errors. While the first will cover a large area, the last two are, obviously, on a satellite by satellite basis. Once you get all the WAAS data for a satellite, it then (and not before) becomes available for use in a WAAS-enabled solution (that's when that satellite's bar shows the WAAS indicator).

 

That's how it's sometimes possible to end up with only a few WAAS enabled birds, and end up with a poorer solution using it, than without it. I'm not saying that happens very often, but it does happen, and that's why the statement that WAAS will always give you better results, is false.

 

I'll end this with a quote from Joe Mehaffey's excellent article on the what's and why's of WAAS:

 

How much improvement in accuracy can I expect when WAAS corrections are working properly?

Answer: This is difficult to say with any certainty. We have observed that MOST OF THE TIME WAAS appears to improve averaged accuracy at a fixed location for maybe 5 minutes averaging from about 7 meters to perhaps 3 meters. Sometimes there has been no improvement and a few times (when WAAS signals were not of good quality or when we were far from a WAAS correction station) the measurements have actually had more error with WAAS than without.

 

The upshot of this is: WAAS is a tool for casual GPS users. It is not guaranteed to work, it is not guaranteed to increase accuracy, it is not really able to tell you when it will improve accuracy, when it will have no effect, or when it will make for less accuracy than the normal GPS signal. Under good conditions when YOU ARE OUT IN THE CLEAR AND RECEIVING A GOOD SIGNAL FROM THE WAAS SATELLITE, you should get both improved accuracy and improved position stability. YOU must insure that you have the proper conditions so as to experience the improvement at YOUR location.

 

This is just the way it is and remember: If you do not like the current limitations of WAAS there is a very simple option -Turn it off.

Joe Mehaffey's article is from 2002. It is now 2005. They descirbe WAAS as simply experimental at the time, and there were outages and such in that phase. WAAS is now offically up and running (as of last july I think), and some of what they stated is no longer true. Some never was true. Their point about being to far from a station is in error. That is the beauty of the modeled WAAS system. As long as you are in the service area, nothing to do with distance from a station, you are good to go.

Here is a better, more up to date site: http://www.gpsinformation.org/dale/dgps.htm

 

I'll admit that I am always on a learning curve, sometimes retention is not great and I have to review and re-learn. I think you are correct on the first point. But as far as enabled birds, understand that WAAS does not kick in till you have 4 birds up. Those 4 birds are giving good correction data. The issue is geometery of the birds. Though a 12 channel reciever is tracking up to 12 birds, it only uses 4 at any one time if I recall correctly. The good part about haveing more than just 4 tracked is that if there is better geometry, or one is lost, the unit can jump to another or better positioned sat for the solution. Running on WAAS the best solution for geometery is still going to apply. If WAAS and Non-WAAS are not mixed (and I'm still not certain on that) there is nothing to say that those intial 4 WAAS sats do not do the job, and certainly as sats are added in the solution get better especially with the corrections. There is also the question of whether 4 corrected sats in a worse position is not better that 4 non- corrected sats with better geometry. It depends on how much correction is needed at the time.

 

As far as I am concerned I use WAAS all the time except when I am in heavy tree cover and know I cannot get the low WAAS sats. Why, mostly just fascination with the technology and if the accuracy is there why not use it?

[+EraSeek]

Just as a practicle little test I just stepped into my yard where I know I have a view of one WAAS sat. After firing up the map76 and aquiring satellites and a position, I had "D's", one by one, on all 7 bars I had up within 60 second.

[+fizzymagic]

WAAS data contains corrective information on ionospheric disturbances, timing and satellite orbit errors. While the first will cover a large area, the last two are, obviously, on a satellite by satellite basis. Once you get all the WAAS data for a satellite, it then (and not before) becomes available for use in a WAAS-enabled solution (that's when that satellite's bar shows the WAAS indicator).

Sorry, the above is just not true. It only applies to defective firmware from Garmin. Magellan units treat the three corrections independently (as they should) and apply whatever corrections are available to each satellite. The unit never ignores a satellite because it does not have complete WAAS information.

 

If any Garmin units still behave as you describe, they are defective and should be either upgraded r returned for service.

[+sbell111]

Funny thing happened this morning, which may or may not have anything to do with this thread. On my way to the airport, I fired up my V. I watched as it locked onto the sats and computed epe. It had a good lock on about seven sats with an approximated accuracy of 13 feet. It then locked onto WAAS and began computing the diff accuracy. All the sudden it has the accuracy at 86 feet. Within a minute or so, it was down to 8 feet and then six as it got the info from each sat.

[+Team Cotati]

WAAS data contains corrective information on ionospheric disturbances, timing and satellite orbit errors. While the first will cover a large area, the last two are, obviously, on a satellite by satellite basis. Once you get all the WAAS data for a satellite, it then (and not before) becomes available for use in a WAAS-enabled solution (that's when that satellite's bar shows the WAAS indicator).

 

That's how it's sometimes possible to end up with only a few WAAS enabled birds, and end up with a poorer solution using it, than without it. I'm not saying that happens very often, but it does happen, and that's why the statement that WAAS will always give you better results, is false.

 

I'll end this with a quote from Joe Mehaffey's excellent article on the what's and why's of WAAS:

 

How much improvement in accuracy can I expect when WAAS corrections are working properly?

Answer:  This is difficult to say with any certainty.  We have observed that MOST OF THE TIME WAAS appears to improve averaged accuracy at a fixed location for maybe 5 minutes averaging from about 7 meters to perhaps 3 meters.  Sometimes there has been no improvement and a few times (when WAAS signals were not of good quality or when we were far from a WAAS correction station) the measurements have actually had more error with WAAS than without.

 

The upshot of this is:  WAAS is a tool for casual GPS users.  It is not guaranteed to work,  it is not guaranteed to increase accuracy,  it is not really able to tell you when it will improve accuracy,  when it will have no effect,  or when it will make for less accuracy than the normal GPS signal. Under good conditions when YOU ARE OUT IN THE CLEAR AND RECEIVING A GOOD SIGNAL FROM THE WAAS SATELLITE,  you should get both improved accuracy and improved position stability.  YOU must insure that you have the proper conditions so as to experience the improvement at YOUR location.

 

This is just the way it is and remember:  If you do not like the current limitations of WAAS there is a very simple option  -Turn it off.

Joe Mehaffey's article is from 2002. It is now 2005. They descirbe WAAS as simply experimental at the time, and there were outages and such in that phase. WAAS is now offically up and running (as of last july I think), and some of what they stated is no longer true. Some never was true. Their point about being to far from a station is in error. That is the beauty of the modeled WAAS system. As long as you are in the service area, nothing to do with distance from a station, you are good to go.

Here is a better, more up to date site: http://www.gpsinformation.org/dale/dgps.htm

 

I'll admit that I am always on a learning curve, sometimes retention is not great and I have to review and re-learn. I think you are correct on the first point. But as far as enabled birds, understand that WAAS does not kick in till you have 4 birds up. Those 4 birds are giving good correction data. The issue is geometery of the birds. Though a 12 channel reciever is tracking up to 12 birds, it only uses 4 at any one time if I recall correctly. The good part about haveing more than just 4 tracked is that if there is better geometry, or one is lost, the unit can jump to another or better positioned sat for the solution. Running on WAAS the best solution for geometery is still going to apply. If WAAS and Non-WAAS are not mixed (and I'm still not certain on that) there is nothing to say that those intial 4 WAAS sats do not do the job, and certainly as sats are added in the solution get better especially with the corrections. There is also the question of whether 4 corrected sats in a worse position is not better that 4 non- corrected sats with better geometry. It depends on how much correction is needed at the time.

 

As far as I am concerned I use WAAS all the time except when I am in heavy tree cover and know I cannot get the low WAAS sats. Why, mostly just fascination with the technology and if the accuracy is there why not use it?

I am curious. Why would you want to disable WAAS while under dense tree cover?

[+EraSeek]

To free up 2 extra channels that thw WAAS sats use. I know they are lower on the horizon and perhaps less likly to get in that situation than some other sats.

[+EraSeek]

Funny thing happened this morning, which may or may not have anything to do with this thread. On my way to the airport, I fired up my V. I watched as it locked onto the sats and computed epe. It had a good lock on about seven sats with an approximated accuracy of 13 feet. It then locked onto WAAS and began computing the diff accuracy. All the sudden it has the accuracy at 86 feet. Within a minute or so, it was down to 8 feet and then six as it got the info from each sat.

Yes, that always happens. When locking on WAAS it will always jump up much higher before it drops down lower.

[+WhatsRNutts]

I have the owners manual and have tried doing everything it says to do step by step...  maybe I'm just not getting it... ill try again...thank you!

OK. A little more research turned up this info.

 

The first thing you want to do is put in brand new batteries. You're going to need them.

 

Do NOT do a master reset on this unit. Instead, clear you autolocate info by holding down the page button as you power the unit up.

 

Next, make sure that the unit is in autolocate mode.

 

Place the unit outside where it has the best view of the most sky as possible.

 

Leave it there. It may take an hour (or two) to get a lock. Once you have a lock, leave it out there for as long as possible so it can update ephemeris data from all of the sats.

thank you so much sbell!! I will try this first thing tomorrow morning. I was out doing a fund raiser and then doing like 4 hours of caching. so I am terrible tired and sunburnt. ill replyback tomorrow whether or not it works... thank you again for doing all that research for me.

ok. I sat outside for almost 2 hours in a big field. It went through 1 satellite after another. only one ever showed up on the display but the number on it changed. it cycled through about 35 approximately 5 times but nothing ever changed after than... also while I was sitting out there my screen sarted going really light... I couldn't hardle see what it said.. i think I am going to give this one up and just buy a new one... I don't have the patience for this...lol

[Digital_Cowboy]

WAAS *may* put you closer to the coordinates, but you don't know if the hider used it when they placed the cache, so it is no guarantee. They may have had an error of 100' when they marked the coordinates.

Ok, that brings up a question that I have.

 

Let's say that I go out and I hide a cache with my Garmin eTrex Legend. WITH WAAS enabled I have say a 10' accuracy reported by the unit. Does that mean that IF another cacher goes out and THEY have a Garmin eTrex Legend also with WAAS enabled and they're given a 10' accuracy. That they'll find my cache at the exact location that I posted?