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Surveying Through Solid Walls.

pdf icon Surveying Through Solid Walls. (1550 K)
Stone, W. C.

Automation and Robotics in Construction, 14th International Symposium. Proceedings. June 8-11, 1997, Pittsburgh, PA, 22-40 pp, 1997.


walls; electromagnetic wave propagation; metrology; non-line-of-sight; signal attenuation; spread spectrum radar; surveying; wireless communications


A good metrology system in the automated environment must (1) measure the three dimensional position and attitude of any component to a reasonable degree of accuracy; (2) acquire these data fairly rapidly; and (3) be capable of making reliable measurements anywhere on site. A significant limitation for existing surveying systems (including GPS and laser based technologies) is the requirement for direct line-of-sight betwwen the reference and roving surveying elements. Construction sites, as a rule, are highly unstructured environments and clutter is the norm. Recent fundamental research has been undertaken at NIST to develop a real-time Non-Line-of-Sight measurement system capable of tracking to 10 mm accuracy despite the presence of walls, ceilings, floors, and other obstructions. The new system determines the distance from a series of reference transmitters which broadcast pulse-synthesized baseband electromagnetic signals. Digital signal processing techniques are used to recover the time of flight (and hence distance) and to compensate for errors introduced as a result of material penetration and re-transmission of the signal. Results are disucssed.