Why would a certified installation be accurate? The difference is almost wholly just paperwork (and price
).
Certainly it is not holy writ that certified installations are perfect. However, many installations could be thought off (and some are flying right now) that send out ADS-B data that is misleading. Certification is one method of ruling out installations that just don't work.
How will he be navigating then?
What happened to VORs/ NDBs / DME's/ dead reckoning / eyeball & the good old map? Are you implying that GPS without RAIM should be used as sole means of navigation?