To WAAS or not to WAAS

[+bpwilldo]

I've searched. Seen people use it and some don't. Seems like a no brainer since it is supposed to improve accuracy of the receiver. However, testing here-

http://www.fs.fed.us/database/gps/mtdcrept/accuracy/index.htm

would indicate some receivers are better with WAAS and some aren't.

So, what's up with this? Does it depend on where you are? Some brands better than others? Anyone know?

Thanks in advance,

BP

[+Atlas Cached]

WAAS assistance depends greatly on your present location in relation to the WAAS satellites, and weather or not you have any obstructions between you and them.

 

If your GPSr is in line of sight and can receive WAAS information, you will have a more accurate position reported to you.

 

Some info on WAAS and EGNOS here.

[+Atlas Cached]

I never bother with WAAS. My Etrex 20 is so accurate using GPS plus GLONASS I can't see the point

 

Show Off

 

I am looking forward to Garmin adding GLONASS to the Montana, or next version of. Until then, I'll WAAS ;-)

[+garyg51]

Dumb question probably - I did read the information referenced above by Atlas Cached - does using both the GLONASS and the WAAS cause any degradation of accuracy?

[+Atlas Cached]

Dumb question probably - I did read the information referenced above by Atlas Cached - does using both the GLONASS and the WAAS cause any degradation of accuracy?

 

Shouldn't, but will eat the batteries up much faster

[+BlackRose67]

I never bother with WAAS. My Etrex 20 is so accurate using GPS plus GLONASS I can't see the point

I've been finding that GLONASS doesn't always work well for me when out in the open (coords can be off by as much as 6 to 9 metres), but does help when under a tree canopy.

[+Glenn]

I never bother with WAAS. My Etrex 20 is so accurate using GPS plus GLONASS I can't see the point

I've been finding that GLONASS doesn't always work well for me when out in the open (coords can be off by as much as 6 to 9 metres), but does help when under a tree canopy.

 

Doesn't seem to make any difference on mine, accurate in the open as well as in wooded areas

 

Since GLONASS and GPS use almost the same frequencies it is difficult to believe, from a physics standpoint, that anyone could notice a difference between the two systems concerning tree cover. GLONASS is currently the most accurate of the two systems but only by a little. This is mostly because they are using newer satellites with the latest technology.

[jholly]

I never bother with WAAS. My Etrex 20 is so accurate using GPS plus GLONASS I can't see the point

I've been finding that GLONASS doesn't always work well for me when out in the open (coords can be off by as much as 6 to 9 metres), but does help when under a tree canopy.

 

Doesn't seem to make any difference on mine, accurate in the open as well as in wooded areas

 

Since GLONASS and GPS use almost the same frequencies it is difficult to believe, from a physics standpoint, that anyone could notice a difference between the two systems concerning tree cover. GLONASS is currently the most accurate of the two systems but only by a little. This is mostly because they are using newer satellites with the latest technology.

and the GPS constellation is being upgraded now with the IIF satellites. I forget if this block has the L2 signal or not, but the IIIA satellites targeted for 2014 and beyond will have the L2 signal for improved accuracy. This, of course, is if the handheld unit includes that capability.

[John E Cache]

WAAS satellites can be used for navigation, but they are on very high geosynchronous orbits. The main use is to get the current errors for ground stations that have fixed known locations. If you are close to a ground station they assume you have the same transmission error and and your GPS corrects the error. So yes, it does depend on where you are. I have a ground station very near me.

[tr_s]

 

Since GLONASS and GPS use almost the same frequencies it is difficult to believe, from a physics standpoint, that anyone could notice a difference between the two systems concerning tree cover.

 

From what I've read, Glonass has a more pole-prioritized constellation - higher probability of satellites being close to zenith at northerly latitudes. Sussam is somewhere in the UK and I'm in Stockholm, so both rather far north. Have also noted strongly improved accuracy by using GPS+GA under tree cover. In the open using merely GPS seems better.

[+Glenn]

 

Since GLONASS and GPS use almost the same frequencies it is difficult to believe, from a physics standpoint, that anyone could notice a difference between the two systems concerning tree cover.

 

From what I've read, Glonass has a more pole-prioritized constellation - higher probability of satellites being close to zenith at northerly latitudes. Sussam is somewhere in the UK and I'm in Stockholm, so both rather far north. Have also noted strongly improved accuracy by using GPS+GA under tree cover. In the open using merely GPS seems better.

 

This is really strange. I don't understand how a GPSr can work better when the signal is being blocked by tree cover. That would be like saying "my GPSr works better inside my house than outside my house."

[+Rotareneg]

 

This is really strange. I don't understand how a GPSr can work better when the signal is being blocked by tree cover. That would be like saying "my GPSr works better inside my house than outside my house."

 

He's not saying the GPS is more accurate under trees than in the open, he's saying that turning on GLONASS reception helps keep the accuracy closer to normal when under trees which are partially blocking the GPS signals as opposed being out in the open.

 

If you've got a clear view of the sky, I personally wouldn't use both at the same time, but in a city or under trees all the extra satellites visible can really help.

 

As far as WAAS goes, if I were in a forested area where keeping a solid track on the WAAS signals is going to be unlikely I might turn it off, perhaps freeing up one channel depending on how the particular receiver works, but otherwise I always leave it on.

[+Glenn]

He's not saying the GPS is more accurate under trees than in the open, he's saying that turning on GLONASS reception helps keep the accuracy closer to normal when under trees which are partially blocking the GPS signals as opposed being out in the open.

 

Ah, that makes more sense. Thanks for explaining it to me.

 

Just think only 7 more years until Galileo is fully operational!