from
http://www.asy.faa.gov/safety_products/GPSSafetyAdv.htm
RAIM for Integrity
... The GPS technical standard order (TSO) requires all IFR-approved receivers to have RAIM. A RAIM algorithm works by overdetermining position using at least five satellites or four satellites and a baro altitude input from an encoding altimeter or altitude encoder. The receiver will sound a RAIM alarm (an annunciator light) if one or more satellites are providing questionable data.
The RAIM alarm limit for en route operations is 30 seconds; for nonprecision approaches, it's 10 seconds, meaning the receiver must be capable of detecting an integrity fault in that amount of time. For future GPS precision approaches, the RAIM alarm limit will be six seconds. If a RAIM alarm is active, the receiver will continue to navigate in en route mode, but it will not operate in approach mode until the RAIM limitation is resolved. RAIM will be the primary means of assuring integrity until the wide area augmentation system (WAAS) is fully operational.
27/09
Also the human readable version is quite handy when you are planning the flight, so that you know RAIM will be available at you ETA before you even light the fires.
I can see that that would be usefull, but as I don't need to do approaches in crappy weather, I would prefer to have much slimmer ARFOR/TAF/NOTAM printouts.
Perhaps the NAIPS briefings could have another user-selected option to generate a seperate GPS RAIM briefing ? ala the MET/NOTAM/Head Office NOTAM options on the NAIPS software.