differential gps today!

[Chris G]

Is it me or has the waas system been turned on today, 'cos when I got to work today the sat status was showing a little D in all the channel status bars

Accuracy 4ft by the way!!

 

[DodgyGeeSer]

Is the WAAS system location specific?
I only have a rough idea of how it works, i.e. ground based antennas that calculate the potential for error in GPS signals (propagation etc.), and transmit correction information to the satellites, which is then interpreted by the receiver.

So, the GPS device does not pick up information from the antennas, it only picks up the corrected information from the satellites, right? Or does the GPS receiver establish that it is close to an antenna (by picking up a signal from the antenna) and then filter for correction data based on proximity to a WAAS ground station?

So, if I'm based in Ireland, where there may be no WAAS ground stations, WAAS is Fe** all use to me?

 

[DodgyGeeSer]

Oh, and is it the EGNOS system you would be connecting to in Europe, or have they started implementing WAAS in Europe too? And are WAAS-capable receivers compatible with EGNOS?

So many questions.... ;-)

 

[Chris G]

Is the WAAS system location specific?
I only have a rough idea of how it works, i.e. ground based antennas that calculate the potential for error in GPS signals (propagation etc.), and transmit correction information to the satellites, which is then interpreted by the receiver.

So, the GPS device does not pick up information from the antennas, it only picks up the corrected information from the satellites, right? Or does the GPS receiver establish that it is close to an antenna (by picking up a signal from the antenna) and then filter for correction data based on proximity to a WAAS ground station?

So, if I'm based in Ireland, where there may be no WAAS ground stations, WAAS is Fe** all use to me?

Calling PanEuropean to the board please

 

[DodgyGeeSer]

I just found some of my answers Here.

A GPS receiver does not connect to a WAAS base station to determine its proximity. Instead, the satellite transmits corrections which are location independant, as well as additional corrections which are area specific, but are broadcasted based on specific WAAS zones. So your GPS receiver will calculate if are are in a specific zone in the WAAS grid, and then intepret the correction information for that particular zone..

Still not sure about the system in use in Europe..

And is there any down-side to leaving the GPS in WAAS mode? It wouldn't require any additional battery power, right? Does it slow-down position calculation?

 

[DodgyGeeSer]

and here's the WAAS coverage areas:
Non-aviation WAAS in the WAAS aviation coverage area.
Non-aviation WAAS outside the WAAS aviation coverage area.

I'll stop talking to myself now.

 

[Deleted account W]

Still not sure about the system in use in Europe..

I think it will be called EGNOS in Europe, but I don't think it's been made public yet.

Here

 

[PanEuropean]

This topic has been discussed in some detail here on the forum, about 16 months ago, at this thread: WAAS satellite coverage In Europe. If you want to have a browse through it - about 3 pages - that will make you an expert on the subject.

...is there any down-side to leaving the GPS in WAAS mode? It wouldn't require any additional battery power, right? Does it slow-down position calculation?

Sharp question, glad you asked. There are significant disadvantages to turning it on. The bottom line on using SBAS - WAAS -EGNOS in the automotive world is this: Turn it off and forget about it! For a whole variety of reasons, you will actually get worse performance from your GPSR if you turn augmentation on. Satellite based augmentation is designed and intended for use only by GPSRs that have a clear, unobstructed view of the sky at all times, such as those used in marine and aviation applications. In the automotive environment, we frequently have obscured views of the satellite constellation due to trees, buildings, etc., and if you have augmentation turned on, you devote two of your satellite reception channels to augmentation only - thus depriving you from using these two channels to pick up satellites that might actually tell you where you are, instead of leaving you looking at a blinking question mark.

Michael