This is done with a computer connected to a mount with a digital camera in it. The computer takes tousands of shots, tracking where the camera is and then uses weeks of computer time crunching them together into one big image. I'm sure they used a DSLR for this and probably a 400mm.
A standard PSD maxes out at 30k x 30k pixels. Even the PSB format has a ceiling of 300k^2. 111 gigapixels is more than 333^2, so you couldn't 'shop it even if you wanted to.