EGNOS

[+Slug Trails]

When I bought my Garmin Etrex H, the fact it supported WAAS was advertised everywhere. I immediately shrugged off the idea of using it as I was under the impression it was only supported in North America. This is of no use to me as I live in the UK.

 

Correct me if I'm wrong, but I recently discovered that EGNOS is a european version of the American WAAS. Another post on the forum suggests that the correction data comes from the satellites numbered 33, 37 and 39 on the GPS.

 

After reading up online, I gather that the EGNOS system has been up since 2004. The WAAS and EGNOS signals are also transmitted in the same 'format', so a device supporting one would also support the other.

 

This made me curious as to if it would work on my Etrex H in the UK, so today when sat in an open car park, I enabled the option and watched the satellite screen. The display changed to 'Ready to navigate diff: 10ft' and a total of 7 D's appeared on some of the satellite bars - from a total of 11. This was after 15 minutes of the GPS being on, so it didn't happen straight away.

 

When I had WAAS disabled on the device, I also got a supposed accuracy of 10ft. The only difference in co-ordinates was one-thousandth of a minute of the Longitude. 54.209 as a pose to 54.210.

 

My question is, and the point of this post is, is the EGNOS system really worth using from the UK? I didn't see an increase in accuracy, the battery is not meant to last as long, it took me 15 minutes to establish the corrective signal and all the satellites (33, 37 and 39) were appearing from just the South (I'm not sure if this changes, but if not then I presume you would have to have a clear view of the South for it to work).

 

Thanks

Edited September 4, 2008 by Slug Trails

[+Prime Suspect]

 

Correct me if I'm wrong, but I recently discovered that EGNOS is a european version of the American WAAS. It doesn't use ground stations, though, but rather the signal is transmitted from certain satellies (numbers 33, 37 and 39 on the GPS).

OK, I will. EGNOS uses ground stations, just like WAAS. And just like WAAS, the correction data comes from the satellites. The ground stations communicate only with the satellites, not GPS receivers.

[+Slug Trails]

OK, I will. EGNOS uses ground stations, just like WAAS. And just like WAAS, the correction data comes from the satellites. The ground stations communicate only with the satellites, not GPS receivers.

 

Thanks... Better edit my original post slightly as to not confuse or misinform others

[+hogrod]

If EGNOS is anything like WAAS when you first enable this it does take the unit a bit to lock on the signal, maybe even 10minutes out in the open. After getting this signal the first time, the next time you use your GPS it will usually get WAAS in under 2minutes.

 

I also noticed it doesn't do that much to improve accuracy, and in the woods were signal would need to be improved the most, your probably not going to get WAAS anyway.

[+trainlove]

WAAS is the Americanized name for the whole world of the Satellite Based Augmentation System that includes WAAS, EGNOS, MSAS and some other future proposed ones for some foreign countries like India.

 

It should be called SBAS but that would confuse people even more, LOL.

 

Yes, ground stations at very precise locations process the signals fromthe GPS satellites and using their known position figure out how the atmosphere interacted with the microwave signals. They then calculate some kind of correction that negates the effect of that interferance and broadcast it to the SBAS satellites. A GPS receiver will pick up those corrections from the SBAS satellites and decide if it should use them on some of the particular GPS satellite signals that your GPS receiver is picking up from your current location.

 

To pick up 'WAAS' signals you need a good view of the Clark Belt of geosynchronous satellites. A problem in the woods and in higher latitude countries. You have to be in an area covered by the corrections they transmit.

 

I've gotten the Fast and Long corrections in mere seconds but due to Magellan GPS receivers kindergarten firmware problems I've never received Iono corrections. Well at least not since I've started to work on a problem mentioned in my web page http://ray.jerome.jobs.googlepages.com/majormagellanproblem

Edited September 5, 2008 by trainlove

[+Prime Suspect]

To pick up 'WAAS' signals you need a good view of the Clark Belt of geosynchronous satellites. A problem in the woods and in higher latitude countries. You have to be in an area covered by the corrections they transmit.