With many RNP procedures, especially RNP-AR, part of the preflight is the RAIM Prediction Report. If dispatch or crew determines there is not sufficient GPS coverage, the procedure cannot be used. Currently your typical RAIM report is NPA (arrival and alternate airports), and route. If the SID is RNAV, a RAIM check is required.
AUGUR RAIM Prediction
https://sapt.faa.gov/raim-summaries....Type=129001450
Many of the mountainous routes in China, the only procedures are RNP AR, so the RAIM check is imperative for both RNP AR departure and RNP AR approach.
Here is what you need for RAIM, minimum of 5 sats for fault detection, 6 sats for fault detection and exclusion. The HPL is also a consideration.
The FMS is always calculating RAIM, and enroute always governs over prediction, so this can have quite the effect on the flight.