Conventional RDF from an airplane making a "running fix" as it flys along takes only seconds today to fix you within a few hundred meters, or closer with better gear located on the ground, after they have gotten your rough position.
It works much better in the country, where your signal is not reflected and "ghosting" all over the place, it's MUCH tougher to find you in a city where false images abound due to the abundance of ferrocement structures and electrical wires etc etc.
Really, I STRONGLY suggest you read "Killing Pablo" to learn about this subject.