Between 1 and 3m depending on where you are. I've played with an 11-16 lens and got some OK shots, but I'd need to go back and do the whole crag (not that hard really, it's only short). For an overview I think it might be better to go to Crosslands Rd on the far side with about a 300 zoom and shoot across the valley (That's how I found the crag!). Because of the ledge the only tree which would really interfere is a large casuarina in front of Induction at the left end of the crag.
And I think one of the shops is doing RC helicopters with a "720p" camera for under $100. Probably IR control which means it wouldn't work to well in daylight. Maybe I should nick my brother in law's quad rotor FPV thingie and crash it into either the cliff or the river!