In Peru, home to the spectacular Inca city of Machu Picchu and thousands of ancient ruins, archaeologists are turning to drones to speed up sluggish survey work and protect sites from squatters, builders and miners. Remote-controlled aircraft were developed for military purposes and are a controversial tool in U.S. anti-terrorism campaigns, but the technology’s falling price means it is increasingly used for civilian and commercial projects around the world. Small drones have been helping a growing number of researchers produce three-dimensional models of Peruvian sites instead of the usual flat maps – and in days and weeks instead of months and years. Speed is an important ally to archaeologists here. Peru’s economy has grown at an average annual clip of 6.5 percent over the past decade, and development pressures have surpassed looting as the main threat to the country’s cultural treasures, according to the government. Researchers are still picking up the pieces after a pyramid near Lima, believed to have been built some 5,000 years ago by a fire-revering coastal society, was razed in July by construction firms. That same month, residents of a town near the pre-Incan ruins of Yanamarca reported that informal miners were damaging the three-story stone structures as they dug for quartz. And squatters and farmers repeatedly try to seize land near important sites like Chan Chan on the northern coast, considered the biggest adobe city in the world. Archaeologists say drones can help set boundaries to protect sites, watch over them and monitor threats, and create a digital repository of ruins that can help build awareness and aid in the reconstruction of any damage done. Hoyle said the government plans to buy several drones to use at different sites, and that the technology will help the ministry comply with a new, business-friendly law that has tightened the deadline for determining whether land slated for development might contain cultural artifacts.