Best resolution for huge banners - 47 by 3 meters?!?

I want to create a banner for the fence of an apartment building 47 meters by 3 meters. Its going to have several pictures. I'm concerned about the quality of the images. I'm worried that they may look pixelated when I enlarge them!

What resolution size or pixels for the pictures do you think would be best for say 5 by 3 meters?
How do I even make sure it wont be pixelated before printing it on a canvas?

Thanks