It is not unlikely that a civilization as ingenious as the Incas could stumble upon elementary surveying techniques, and use them to create these drawings. The priests were also waaaay into hallucinogenic drugs, which made them feel completely dissociated from the earth, like they were flying, and they probably put these designs on the ground so they could appreciate them while they were 'flying' about in their psychedelic stupor. Seriously, anyone who was at all motivated (like the religious) could produce works like these. We are amazed only because the Incas were the only people to do something like this, and Peru is one of the few places where millenia-old etching would still be evident and uneroded.
