New Scientist has a popular version of an article in the Journal of Archaeological Science about recording the locations of archaeological artifacts using acoustic signals.

Every object unearthed by an archaeological dig must have its exact position recorded. This is normally a painstaking process involving measuring rods and string, but a device that uses technology originally developed to guide robots could speed up the process.
Gran Dolina in central Spain is a Palaeolithic site that contains important hominin remains which date from between 780,000 and 300,000 years ago. Thousands of fossils are discovered there every year, but registering them all by hand makes progress frustratingly slow. So archaeologists working on the site contacted Angélica de Antonio Jiménez and Fernando Seco at the Institute of Industrial Automation in Madrid, to see if they could come up with a better way.
Antonio Jiménez and Seco were working on an ultrasound system to help blind people and robots navigate, in which a mobile transmitter sends signals to a network of fixed nodes. The time taken for the signal to arrive at each node determines the precise location of the transmitter. To adapt the system for archaeological sites, Antonio Jiménez developed a 2-metre-long pointer, like a big pencil, to act as the transmitter. To prevent the user’s body blocking the signals, it has two transmitters, one at the top and one 70 centimetres below it.
When a researcher finds an object, they trace its outline with the pointer, transmitting ultrasound data to a network of nodes above the site.
Software then reconstructs not only the position of the object, but also its size, shape and orientation, to an accuracy of about 5 millimetres (Journal of Archaeological Science, DOI: 10.1016/j.jas.2009.06.027).

The New Scientist article continues here.

HT: Joe Lauer