Amazing chalk arts spoted on the streets of Torronto

Hi, This is my first post. let it be something useful and mind blowing. These are some of the good chalk arts from the streets of Toronto done by Grassroots.

I don’t have any idea how do they guys draw these big images. Anyway these pics really pulls everybody's attention.

 No doubt to their creativity, But I am trying to figure out how do they do this mind blowing art