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Asked by: 489 views FAA Regulations, Instrument Rating

So from my understanding that, we need at least 5 visible satellites in order to calculate RAIM. RAIM only calculates HPL(Horizontal protection Level) but WAAS does something even better; HPL + VPL(Vertical Protection Level).

Now from my understanding, WAAS stations receive L1, L2 Satellites information directly to calculate and generate WAAS message to further correct signal and shoot them to WAAS satellites.

My question is that why do we still get LOI on G1000 when we have less than 4 visible satellites when WAAS is on ? (even though WAAS further fine tunes the signal...)

Also, with WAAS, is WAAS technically doing RAIM + VPL calculation or HPL + VPL calculation? Does the techincal word 'RAIM' applicable to WAAS?

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