[Dugie8]

You basically have it. RNAV and GPS are the same thing. The old (god it hasn't been that long) RNAV units where basic trig calculators, you could enter in a VOR freq a radial and distance and fly to that point just as if it was a VOR (radials to from). There were/are?? approaches that were RNAV approaches that you set up these waypoints based off a nearby VOR. I flew some PA28s that had these units, worked great, there were/are?? charts designed for using those RNAV units. All the VORs had bold lines for N, E, S and W and you simply drew your course and entered in waypoints as they crossed those cardinal radials.

Now, with the advent of GPS and how widespread it is, GPS has become RNAV on the approach plates, instead of GPS RWY 17.