Originally Posted by
dbenj
Apples and oranges. Your iPad GPS is not certified, therefore your position is not precisely depicted on your iPad. But the GPS used by ADS-B in the aircraft around you are WAAS certified and accurate typically to 3 ft. horizontally and 5 ft. vertically. (The certification standard in less precise.) So the positions of the surrounding aircraft depicted on your iPad are more accurate than your position depicted on your iPad.
Better than controllers being completely blind in the fog.
I use the ADS-B traffic feature on the ground on my iPad all the time to see how many there are waiting for departure, so I can plan my second engine start. Airplanes pop up and disappear all the time. I was a non-radar ATC controller in training. Pretty much the legal definition of controlling blind. It was perfectly safe, as long as you followed the rules. Adding radar made it possible to add more traffic, with the same level of safety. But also with much less time to react if something went wrong...
Until there is a certified system, which as you said, takes time and money, I will go with:
"It is better to know you are blind, than think you can see."