To start with...
RNP & RNAV have nothing in common (assume)
RNAV is a method of navigation..... RNP is part of a concept viz Performace Based Navigation
RNAV
A method of navigation which would allow the system to take any desired path/course within the coverage of nav beacons/or the navigation system
PBN-> method of navigation is dependent on the performance of the nav equipemnt
RNP -> The regulatory number (rnp .3 1 5 10) to be complied with to fly in the airspace/route/procedure with which it is associated.
Only when it is certain that my equipment has an ANP(actual nav performance) for at least 95% of the time equal to or better than RNP can i be allowed to fly any track/path/route that i may want to.
eg
DEL-MAA
Conventional route- vor to vor -> DPN BPL HIA MAA
RNAV route -> DPN abeam BPL abeam HIA maa
THe abeam points have been mathematically made (pseudo ranges/ghost stations) by the system, the end result would be a straight line b.w DEL and MAA
Systems such as DME DME can be used only when they remain within the coverage are of the beacons i.e DPN,BPL,HIA,MAA any 2 atleast at all times
same for VOR VOR
more morden systems such as gnss give me a wider coverage are such as north pole to south pole
so RNAV and RNP have nothing in common but are related .to be able to do RNAV ANP needs to be RNP or better that is what is common b/w them