This is my final line drawing for my walking city.  I traced over my pencil drawing which was on tabloid paper with two 9.6 x 8.5 sheets of tracing paper and a size 1 micron.  I might have to go over some of the lines toward the middle in Photoshop but other than that I'd say it's a pretty effective technique if you want to do a traditional drawing.  I left some parts blank because their either going to be covered in dust from the desert or I planned on copying a part of my drawing and sliding it into place.  The legs in the back ground are going to be more hinted at in atmospheric perspective to really make this thing look big. Now I just gotta paint it.