Just a clarification here, but it is my understnading that GPS usage in the UK and Europe cannot currently benefit from WAAS so why do so many shops and sites state this as a benefit to purchasing said model over another. Obviously if you are going to use it in the states there is reason, otherwise is it not pointless?

Should be up and running now. It's known as EGNOS in Europe and the signal was activated in July this year.

my handset isn't WAAS enabled (Geko 101), does anyone have one that is and have noticed a difference?

WAAS is enabled in the UK and DOES give significantly improved accuracy.

My GPS60 has it and once enabled, it does make a significant difference.

See the ESA EGNOS website for information on EGNOS and WAAS.

i've not really noticed all that much difference whilst walking. my gps usually give me accuracy down to 3m on a good day and usualy around 6-8m on others without waas enabled. waas improves that to around a consistent 4m. good if i was cache hunting.
the usefulness of increased accuracy for general walking is possibly debateable as maps aren't that accurate to begin with.

egnos is on but hasn't been declared "live" yet as further testing is being undertaken before they are confident of it "going critical" i.e. fully up and working e.g. you can blind land an aircraft.

i think the egnos satellites are numbered from 31 (or is it 30) so you can see on the display whether you've got one captured or not.



edit: aha! the capt has the very site above

Has the problem regarding poor/no signal at more northern latitudes (i.e. Scotland) been resolved yet?

If its the problem I think you mean, it needs the Galileo satellites before that problems gone. As the satellites are in geostationary orbit over the equator resolution as you trave l both north and south from the equator diminishes.
Galileo aims to eradicate this problem

Generally though, when I've managed signal in Scotland its been of a good quality (<10m accuracy)

It's aye been <10m accuracy - with WAAS switched off.

When my Legend C is listening to an EGNOS satellite a "D" appears in the bottom of each of the bars on the the bar chart screen which represents an EGNOS enabled satellite thus alerting me to that fact. I imagine other models do similar things. I understand that "D" stands for "differential". There now, I have exhausted my knowledge of this area!

I haven't done a back to back comparison with WAAS switched on or off so I can't say how much more accurate the GPS is with it switched on. I shall go and do that comparison this w/e.

i thought that about the D too. but unfortunately it isn't. you need a lock on a satellite numbered 31 (or 30?) or above which are the waas/egnos ones.

To clarify the above when looking at the Advanced Skyview page on a Garmin GPS.

Satellites numbered above 30 are WAAS/EGNOS transmitters, these transmit a differential correction signal for each of the GPS satellites. If a WAAS/EGNOS differential correction has been received for a GPS satellite then it's signal bar will have a "D" on it.

When there are enough GPS satellites are in view which have had a differential correction received from a WAAS/EGNOS satellite then you will have a differential fix and the ACCURACY measure will switch to being a DIFF measure.

It is important to realise that these are different measures.

The ACCURACY measure is determined entirely from the GPS signal, it is generated by estimating the errors in the signals from the GPS satellites. The accuracy measure may be inaccurate as if incorrect signals received from all GPS satellites in view are consistent with each other then you will have a high reported accuracy.

The DIFF measure is determined by the information in the WAAS/EGNOS signals which are generated by considering the signals received by fixed location GPS receivers. This information measures the error in the GPS system and relays it so that non-fixed receivers can both correct for this error and know the accuracy of the system.

As an extreme example. The GPS system could be modified such that each satellite believed it's longitude to be 1 degree greater than it actually was. Each GPS receiver would believe that it had an accurate position as all satellite signals would be consistent even though all positions returned would be incorrect. The WAAS/EGNOS base stations would all receive signals placing them at the wrong longitude, this error measurement would feed into the WAAS/EGNOS signal allowing correction and more importantly identification of the error.

Using my supercheapie Geko 101 I get ~ 5m accuracy and pretty good altitude accuracy (within a few m), such that I can't see in practice that another metre or two of accuracy would be any real use to me, unless I was geocaching.

Well that's the point - normal GPS is accurate enough for most applications but WAAS is just 'extra' accuracy - most new GPS receivers will just include it as standard.

It's not just extra accuracy, it's measured accuracy.

I am impressed. Thanks John and Parky, I didn't know it was 30 or above. Although I did my experiment over the w/e, and got "D" I can't recall if satellite 30 or above was being received. I shall repeat.

i've had the D appear without having a lock on an egnos satellite? how does that work then??

I took a reading with my Geko 201 at the base of Lord's Rake. I had a good strong "D" signal and the readout said that the accuracy was ~ 5m.

Got back home and transferred the data to MM on the laptop. It plotted the mark about 40m due south of the cross on the Scafell saddle, at an altitude of 217m.

:-(

Looking South-West out of my back bedroom window I get D on satellites 3,6,7,16,21 and 25 but not 31 or 33 or 39. Looking North-East out of the front of my house I don't get any D's. That seems broadly comparable to Parky's experience. WAAS is enabled in both cases.