** UPDATED IN LIGHT OF REPLIES THAT FOLLOW, so some of the replies later in the thread may no longer make sense.
I confess to bring a bit confused about the current state of EGNOS (the European equivalent of WAAS) and do did some research. Are my assumptions below correct and have I missed anything obvious?
1) An aviation GPS receiver is more sophisticated than a car SatNav, including features such as RAIM which double check the integrity of the signal received. Often GPS receivers are connected to other instruments such as a CDI or HSI, this being a requirement if used for IFR flight.
2)
EGNOS provides extra information to a GPS receiver which allows it to achieve accuracy of 1-2 metres compared to the normal 19 metres, both horizontally and vertically. This is a wide-area augmentation system that is more accurate than and not the same as Differential GPS (as explained in
approved for "Safety of Life" applications such as aviation approaches in March 2011. It covers all European countries and even parts of North Africa
5) Most UK GPS approaches are classed as a non precision approach and don't provide a glide slope - they are similar to an NDB/DME or ILS localiser only. EGNOS is NOT required for this type of approach. Navigation equipment to handle these Non Precision Approaches can often be installed as an EASA minor mod.
6) A more sophisticated GPS approach is called an LPV which also provides a glide slope just like an ILS. These all require EGNOS to be fitted to be used legally. If the EGNOS signal is not received then the GPS approach cannot be used. Most GPS LPV installations would require a very expensive Major Mod, but Garmin has obtained generic approval for their GTN series which means they can be installed for LPV as a minor mod only (see detailed reply below) Today there is only one in the British Isles today at Alderney - next is Southampton in March, while France now has four (see
list)
7) An IMC rated private pilot probably legally may require further training to use a GPS or LPV approach, regardless of which this might be sensible
8) Fitting an EGNOS capable GPS such as the 430W is not normally a Major Mod, for non-precision approaches, but for LPV would require one and be ludicrously expensive. Garmin has obtained a generic EASA approval for their GTN 750/650 series which means they only require a minor mod.
9) LPV and GPS approaches are available to EASA and Annex II IFR capable aircraft, (not to Permit or VFR only)
10) Unlike in the US, in Europe all GPS approaches must be manned by full ATC service (not a FISO or A/G) when used, but needn't have radar. This will limit the rollout of GPS approaches outside those which already have some form of instrument appriach today.
Thanks in advance
SD
*Editted to incorporate clarifications and corrects from later replies 19/2/12