Alex90,
Thanks for your kind words about CAP1122. It's a shame that the pioneering spirit, within the CAA when we first started to write it, hasn't survived.
For your info there is no EASA AMC/GM to supersede this CAP and it remains a national document, albeit adopted as best practice by a number of European states.
There are virtually no Scheme of Charges figures associated with CAP1122; I recall less than £1000. The real cost is in buying in expertise from IFP designers, safety case authors and Airspace Change Proposal managers. £50,000 outlay with no guarantee of success. That said, money from Europe channeled through the EGNOS promotion fund has helped.
Cessnapete
WAAS enabled receiver equipment goes further than RAIM which is an algorithm derived prediction tool. Did you you know at the start it was calculated on a 'flat Earth' basis so satellite visibility in the valley of a mountainous region wasn't accounted for.
However, Fault Detection and Exclusion (FDE) is what your boxes perform and is an active check in real time, though you need six, I think, satellites in view.
And referring to CAP773 the practice of a gross error check approaching the IAF is described. It's a key pillar that argues against sole means of reference. In other words one should have other Navaids available to help ensure positional verification.