About: http://webisa.webdatacommons.org/146948276

Property	Value
http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://www.w3.org/ns/prov#Entity
http://www.w3.org/ns/prov#value	These devices are now readily available and work by sending out an ultrasound, laser or other types of beams and determining the transit time required for the beam to reach the selected point, and return.
http://www.w3.org/ns/prov#wasQuotedFrom	google.com