Hmm but he was flying over a huge area - from Brooklyn Bridge, Statue of Liberty, apartment buildings on the waters-edge, etc. I'm wondering if they used radio

Hmm but he was flying over a huge area - from Brooklyn Bridge, Statue of Liberty, apartment buildings on the waters-edge, etc. I'm wondering if they used radio direction finder - but a) would they have that equipment to hand and b) how would they know what frequency to be looking on?