Jump to content

Waas


The Saints
Followers 3

Recommended Posts

I recently got my GPS for my birthday. My wife met some geocachers and decided that she would give me this present (for her). It worked. We both love it, and I can use the gps on my kayak.

The unit she bought me has WAAS capability. Everytime I try to use it, it says "Searching for WAAS". I mentioned this to the store where it was bought at and they told me that President Bush turned the WAAS off. Forgive me because I don't know the technical lingo and technology.

 

Thank you,

Scott, Valerie and Daisy dog :rolleyes:

Link to comment

I was out a couple of days ago and my GPS was giving me the big "D" on several channels, so, WAAS is still active here.

 

The problem with WAAS is that it is not everywhere. If you are near an airport you can expect to be receiving it. If not, you likely will not. At least that is my experience and understanding.

Link to comment

They are incorrect. WAAS is on and working fine.

 

The Puzzler's message above is incorrect. WAAS is visible and works fine over the entire continental US. There is no need to be near an airport.

 

Leave your GPS on with a clear view of the entire southern sky for an hour or so. If you are in the eastern half of the US, make sure you can see to the southeast; in the west, tend more to the southwest. It will pick up at least one of the two visible WAAS satellites and should find them more quickly in the future.

 

A GPS unit will not start doing WAAS corrections right away; it has to acquire the satellite and get enough data to start the corrections. Usually, from a cold start, that takes at least 10 minutes.

Edited by fizzymagic
Link to comment

My experience with WAAS is that when you first start to use it, it takes a long, long time. It wasn't until I turned it on and forgot about it that I finally noticed I was gettinga WAAS lock (indicated by the D's in the satalite signal bars) and my EPE was below 10'.

 

Before I forgot about it even if I saw the D's I had an EPE worse than when it was turned off in my GPS.

 

WAAS works you just have to give it time.

Link to comment

Rumors of the Pres disabling WAAS or GPS in general are unfounded, based on some off-hand remark that he had the capability of doing so if terrorists were using it. The military can selectively jam it in areas as needed, and I assume they would do so if necessary. Until then, as pointed out above, you can search your little WAAS off and get good results, once the GPSr has downloaded the correction information, which initially takes a while.

Link to comment
The Puzzler's message above is incorrect.  WAAS is visible and works fine over the entire continental US.  There is no need to be near an airport.

I have to agree and disagree on this. The WAAS signals are primarily from satellites and the do provide coverage for a lot and then some of the continental US. Just remember that satellites part WAAS was designed for airplanes in flight so the satellites are in a less favorable orbit than other geosynchronized satellites (planes are high so they can “see” farther south). There is a part of the system at all major airports that broadcast the signal like the satellites which the GPS also receives it provides the same information that the satellites broadcast. These “fake” satellites are at a lot of airports in addition to the majors. Driving home I go past Ohare, and as a norm my Garmin is indicating an error of 3 to 5 feet.

Link to comment
The WAAS signals are primarily from satellites and the do provide coverage for a lot and then some of the continental US.

WAAS signals are received only from satellites.

 

Just remember that satellites part WAAS was designed for airplanes in flight so the satellites are in a less favorable orbit than other geosynchronized satellites (planes are high so they can “see” farther south).

WAAS satellites are in geostationary orbits. There is only one geostationary orbit. All geostationary satellites (including the WAAS satellites) are strung out along the same orbit. "Further south" has no meaning.

 

There is a part of the system at all major airports that broadcast the signal like the satellites which the GPS also receives it provides the same information that the satellites broadcast.

I think you are talking about LAAS. I was unaware that Garmin receivers were able to receive LAAS without an external unit. If you have any pointers to further information on this, I would be most grateful to see them.

Edited by fizzymagic
Link to comment
WAAS signals are only from satellites.

Somewhat incorrect, depending on how you look at it. The GPS receiver does receive the signals only from the satellites, but the system itself relies on ground stations. From Garmin's FAQ

 

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.

 

Just remember that satellites part WAAS was designed for airplanes in flight so the satellites are in a less favorable orbit than other geosynchronized satellites (planes are high so they can “see” farther south).

Incorrect. There is only one geostationary orbit. All geostationary satellites (including the WAAS satellites) are strung out along the same orbit. "Further south" has no meaning.

 

You're not reading the response properly. The poster was indicating that aircraft do not have obstructed views like we do on the ground, so they can "see" farther south than someone standing under trees or where their view of the horizon is obstructed.

Edited by Jeremy
Link to comment
There is a part of the system at all major airports that broadcast the signal like the satellites which the GPS also receives it provides the same information that the satellites broadcast. These “fake” satellites are at a lot of airports in addition to the majors. Driving home I go past Ohare, and as a norm my Garmin is indicating an error of 3 to 5 feet.

The SCAT-1 and LAAS DGPS correction data is transmitted in the VHF band around 115 MHz whereas consumer GPS receivers get the GPS and WAAS signals in the microwave band around 1500 MHz.

http://www.ntia.doc.gov/osmhome/LRSP/LRSP5a.htm

To the extent that you get better WAAS reception near an airport I'd guess it's due to the fact that airports tend to be put where the terrain (both natural and manmade) is fairly flat and therefore you have less chance of obstructing the signals from the geostationary satellites that are pretty low in the sky.

 

FWIW I just upgraded to a WAAS-capable receiver and frequently got WAAS corrections while driving around the last couple days (without an external antenna).

Link to comment

My Vista would pick up WAAS only when I was in an area with a clear view of the horizon. After being powered up for 20 minutes or so I would see little "D''s pop up on some of the satellites. If it could see satellite 35, I had an accuracy of 9 to 15 feet. This didn't happen very often - I had to be several hundred feet above sea level. Your mileage may vary.

Link to comment
B) Thank you very much for the quick responses. I'll turn it on now and forget about it for a while. Hopefully this doesn't burn an image into my screen.

 

Scott, Valerie and Daisy dog

Screen burn is not a problem with Liquid Crystal Displays. A problem known as temporary image persistance can occur (must be on for an extremely long time) and is similar to "screen burn" but it is reversible.

Link to comment
You're not reading the response properly.

Umm, the poster said

"so the satellites are in a less favorable orbit than other geosynchronized satellites

that doesn't make sense, sorry.

 

FizzyMagic is right.

I'm waiting for someone to argue that the satellites aren't "relatively low in the sky" and/or that it is impossible for WAAS signals to be blocked on the ground. That would put the icing on the cake. B)

 

Fizzy was right and Fizzy was wrong. Jeremy was wrong and Jeremy was right.

Link to comment
Screen burn is not a problem with Liquid Crystal Displays. A problem known as temporary image persistance can occur (must be on for an extremely long time) and is similar to "screen burn" but it is reversible.

This also happens if your LCD gets too hot, such as leaving the GPS on the dash of a car too long in the sun. The image refresh is very sluggish and poor quality, but stick it infront of the Air Conditioner vent for a while, cool it down, and all is good again. Thankfully.

Link to comment
I recently got my GPS for my birthday. My wife met some geocachers and decided that she would give me this present (for her). It worked. We both love it, and I can use the gps on my kayak.

The unit she bought me has WAAS capability. Everytime I try to use it, it says "Searching for WAAS". I mentioned this to the store where it was bought at and they told me that President Bush turned the WAAS off. Forgive me because I don't know the technical lingo and technology.

 

Thank you,

Scott, Valerie and Daisy dog :huh:

What was the name of the store Radio Shack or REI?

 

1st) WASS is not off

 

2nd) you do not need WASS for geocaching

Link to comment
:D Thank you very much for the quick responses. I'll turn it on now and forget about it for a while. Hopefully this doesn't burn an image into my screen.

 

Scott, Valerie and Daisy dog

According to my Garmin users manual, using WAAS does cause batteries to drain a little faster.

 

If you're getting an accuracy of 30-40 feet without WAAS, I'd bet you shouldn't worry about turning it on. That's good enough to find a cache location.

 

Also keep in mind that havng a more accurate reading with WAAS can only help if the person that hid the cache also had WAAS on when recording the location.

Link to comment
According to my Garmin users manual, using WAAS does cause batteries to drain a little faster.

 

If you're getting an accuracy of 30-40 feet without WAAS, I'd bet you shouldn't worry about turning it on.  That's good enough to find a cache location.

 

Also keep in mind that havng a more accurate reading with WAAS can only help if the person that hid the cache also had WAAS on when recording the location.

Sorry, I just can't walk away from this one.

 

1) Yes, WAAS being turned on measurably decreases the battery life of my Garmin Geko 301, I would guess about 20% decrease, which seems to me like a surprisingly large amount.

 

2) Accuracy of 30-40 ft means only a 50% chance of the real position being within 30-40 ft of where your unit says it is, and about a 95% chance of it being within 60-80 ft. I have hunted plenty of caches where decreasing my search radius by as little as 10-15 ft made a huge difference in the difficulty of the hunt. It all depends on the terrain, the ground cover, and the viciousness of the hider.

 

3) The error in your location relative to the cache is always a combination of your error plus the hider's error. The more error the hider has, the more important it is for you to reduce your error so that you don't compound the error problem.

 

If you can get WAAS, and the cache is hidden such that accurate coordinates are an advantage, using WAAS will always improve your hunting regardless of how accurate the original hide was. . . it is simple statistics.

Link to comment
In order to receive WAAS, you need to have a view of either (Garmin numbering) satellite #35 (east coast) or #47 (west coast). If your GPS isn't receiving either one of those satellites, then you won't get WAAS.

 

Thanks to you and Eraseek for the great info. I played with my IQue 3600 today, watching the bars come in and out, and spotting the "D" indicators. I'm East Coast, so I am receiving #35.

 

Tomorrow, I'll watch the system with WAAS turned off, to see if freeing up two channels for additional satellites makes any difference in the accuracy. From what I read on the linked report, it appears there is a certain trade-off, with advantages and disadvantages both ways. (My unit is connected to the automobile battery, so power consumption is not an issue.)

 

-Paul-

Link to comment
Tomorrow, I'll watch the system with WAAS turned off, to see if freeing up two channels for additional satellites makes any difference in the accuracy. From what I read on the linked report, it appears there is a certain trade-off, with advantages and disadvantages both ways. (My unit is connected to the automobile battery, so power consumption is not an issue.)

 

-Paul-

Keep in mind that your GPS's EPE or Accuracy Reading is not true accuracy. It is only an programmed estimate of how well your GPS is doing. When first aquiring WAAS the reading will go way up until the current almanac is loaded, and then it will begin dropping. Generally the way it goes is from about 12 - 20 up to 60 or so before dropping to sub 10, often to about 6'. Improved accuracy depends on how much correction is needed. For instance, at night the ionosphere is not very active so little correction can be made, but mid day or during solar storms a great deal more correction can be made. True accuracy depends on satellite geometery as much as WAAS corrections. The best way to see true difference is to take postions on top of a benchmark where the coordinates are known with WAAS on and off. When I have done that I've noticed about a 40 percent improvment. In terms of actual feet it isn't going to be that much but in terms of actual improvement it is (again dependant upon corrections needed and existant sat geometry).

Link to comment

Keep in mind that the two WAAS satellites will also be used to determine your position, in addition to providing the augmentation data. So you're not really losing the two slots. Well, maybe one slot if you're only picking up one WAAS satellite.

 

But considering I rarely see more than 8 or 9 "regular" satellites at a given time, I'm actually *gaining* satellites by turning on WAAS.

Link to comment
What was the name of the store Radio Shack or REI?

 

We got it from West Marine in Santa Cruz CA.

It is a Garmin 276C maps

I love it

I would have expected more from West Marine, but then again, a few years ago they got rid of most of there experianced employees and hire new staff to cut corners, I guess they got what they paid for.

Link to comment
Keep in mind that the two WAAS satellites will also be used to determine your position, in addition to providing the augmentation data. So you're not really losing the two slots. Well, maybe one slot if you're only picking up one WAAS satellite.

 

But considering I rarely see more than 8 or 9 "regular" satellites at a given time, I'm actually *gaining* satellites by turning on WAAS.

The waas satellites are not part of the GPS constellation and play no part in the position fix other than to provide corrections.

 

To elaborate, the WAAS sats DO provide a GPS ranging code that CAN be used by GPS receivers that have the ability to use them. whether or not our low end units do this or not is really in question. Clearly, we do not have the ability to select whether the WAAS signals are to be used for corrections, ranging or both. We can only turn WAAS on or off. High end receivers used in aircraft generally have the abiltiy to select what they are using WAAS signals for.

Edited by Poindexter
Link to comment
The waas satellites are not part of the GPS constellation and play no part in the position fix other than to provide corrections.

I do believe that is incorrect. The WAAS signal itself is not used for a postion fix (just for correction data), but the sats used for WAAS do carry the normal GPS signal and can be part of the postion fix.

 

"w's" I believe is Magellens version of the "D's".

 

My 40% was incorrect. I noticed that the actual position was 40% better than what the EPE or Accuracy Reading stated. WAAS improvement generally took me down from about 10' or 12' to on the mark to about 6'.

Link to comment
Poindexter, I know nothing about ranging but clearly WAAS is used for corrections to position and time every time we acquire a WAAS signal.

Yes, WAAS is used for corrections, I didn't mean to imply that it wasn't. WAAS sats also send a GPS ranging code that CAN be used in determining position along with the GPS sat's. Our position is determined by computing our distance (range) from the sat's. Do our receivers use the ranging code from the WAAS sat's? Nobody really seems to know. If they do, it would be nice to be able to just use the WAAS sat's for that ONLY and not use the corrections. High end units allow you to do this. Sorry for the confusion. I was trying to say that our low end units don't use the WAAS sat's ranging signal as part of the position fix but in fact we really don't know if they do or not.

Link to comment
Sorry, I just can't walk away from this one.

 

1) Yes, WAAS being turned on measurably decreases the battery life of my Garmin Geko 301, I would guess about 20% decrease, which seems to me like a surprisingly large amount.

 

2) Accuracy of 30-40 ft means only a 50% chance of the real position being within 30-40 ft of where your unit says it is, and about a 95% chance of it being within 60-80 ft. I have hunted plenty of caches where decreasing my search radius by as little as 10-15 ft made a huge difference in the difficulty of the hunt. It all depends on the terrain, the ground cover, and the viciousness of the hider.

 

3) The error in your location relative to the cache is always a combination of your error plus the hider's error. The more error the hider has, the more important it is for you to reduce your error so that you don't compound the error problem.

 

If you can get WAAS, and the cache is hidden such that accurate coordinates are an advantage, using WAAS will always improve your hunting regardless of how accurate the original hide was. . . it is simple statistics.

Sorry, I just can't walk away either.

 

1) Battery drain - not worth the "advantage" in my opinion.

 

2) Once my GPSr gets me within 40 feet or so I put it down and start using my eyes. I think like someone hiding the cache and try to figure out where I would hide it. I also look for signs of other cachers that have been there before me. It's just something you learn to do after several hundred finds. When I was new at this I kept trying to follow my GPSr all the way to the container. My post in this thread was an attempt to help the new people realize there's more to finding a cache than how accurate your reciever is. The GPSr can only do so much.

 

3) If the hider had an error of 40 feet, and I had an WAAS accuracy of 9 ft while looking, I could be 31 feet away but believe that I'm only 9 feet away. In the Walmart parking lot this isn't an issue. In other places (like out in the woods, or night caching) it's enough to throw you off instead of helping if you're relying too much on it.

 

That's why I said that getting within 40 feet is good enough to find the cache location. Getting your hands on the log book will often require you to use your eyes and brain. It's simple logic.

Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
Followers 3
×
×
  • Create New...