Quite incorrect, navaids are no longer an essential network for traffic management.
They are not essential, but some of the are very very useful. Under the separation standards we use NDB's are more accurate than GPS under some circumstances. Also passing over a VOR/DME allows us the "reset" the nav tolerances of aircraft with IRS.
Interestingly this may have ramifications for some of the smaller operators of medium jets (early A320's and 737 Classics), as most of those are not GPS-equipped,
Wouldn't they have IRS? Admittedly that only covers en-route, but people flew non navaid routes long before GPS.
ReverseFlight thats interesting. The way I read that, GPS Primary averages three IRS and the GPS position and ignores navaids. Without GPS Primary, it averages three IRS positions and a radio fix, and adds GPS only if the GPS position agrees. The difference seems to be the trust in the GPS position. Is GPS Primary selected by the crew or the FMS?