Actually to create that pattern is not too difficult because we just need a long rope that tie on the machine and a rope is plug as the center of circle. If a cutter machine driver run carefully so they can create a big smooth circle. Other accessories also still use plugged rope on the machine as the center of the pattern.
A group of Students from Jogjakarta admitted this UFO track is made by them, they made this circle on the night by a grass cutting machine or lawn mower. As this can do by the above description easily. Because the current lawn mower is available in many type and very light, or they can create just by simple tool like "Gerobak" that tie with rope as a center guide.