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 US anti-terrorism campaigns, but the technology's falling price means it is increasingly used for civilian and commercial projects.

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 in Peru. The country's economy has grown at 6.5 percent on average over the past decade, and development pressures have surpassed looting as the main threat to the country's cultural treasures, according to the Peruvian 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.