Well after speaking to Rense de Boer on Facebook (nice guy) he gave me a few tips on his awesome 4k photogrammery work. I've been giving it a go in my spare time. I went into the city taking various photos from different angles. I've managed to get it working pretty well on a fairly large scale. I took it into UE4 and took a few screenshots. Still not as impressive as Rens'... guess I'll just have to keep trying.