Interesting. Why do people assume this could not have been done without GPS? Maps have long been created by triangulation, is there any reason that process could not be used backwards to create a terrain feature from a map?
I'm sure theres a rich history of people claiming the pyramids/great wall/stone henge couldn't have been built without X technology, when they evidently were.
Exactly. Random idea, but one simple way to do it could have been to draw the figure on paper, draw a grid over it, for example with 1cm boxes, and then draw much bigger boxes, say 10 or 100 meters big on the soil. And then just copy box by box and in the end get rid of the grid. Who needs GPS?