NIST Construction Automation Program Report No. 1: Non-Line-of-Sight (NLS) Construction Metrology.
NIST Construction Automation Program Report No. 1:
Non-Line-of-Sight (NLS) Construction Metrology.
Stone, W. C.
NISTIR 5825; 217 p. February 1996.
Available from: National Technical Information Service
construction automation; dielectric constant;
diffraction; metrology; multipath; NLS;
non-line-of-sight; penetration capacity; positioning
system; propagation delay; spread spectrum radar;
This paper addresses the subject of automated metrology
(surveying) for use on construction sites.
Specifically, the research is directed to the
development of a novel Non-Line-of-Sight (NLS) system
with which the real-time position and orientation
(attitude) of any object on a construction jobsite may
be determined, irrespective of the presence of
intervening obstacles that would otherwise render
optical and/or electro-optical techniques useless. Tests
were conducted using a specially configured broad-band,
low-frequency spread-spectrum radar. The transmission
and receiving antennae, which in normal radar are
typically one and the same, were physically separated so
as to create a system with a fixed broadcast unit and a
"roving" receiver, whose range was to be determined
relative to the transmission antenna by means of
time-of-arrival measurements. Time domain response was
synthesized by means of fourier theory from a broad
spectrum of data sampled in the frequency domain.
Numerous field experiments were performed in which
typical construction site obstacles were placed between
the transmitter and receiver with separation distances
of up to 80 meters. The obstacles included a half-meter
thick, heavily reinforced concrete wall, varying
combinations of masonry block and brick up to more than
a meter in thickness, and metal pre-fabricated wall
panels. In all but the latter case, repeatable
distances were obtained. Range detection was lost in
the presence of extensive metal panels that contained no
windows. However, the presence of even small openings
permitted range acquisition. Sources of error, limits
of resolution and accuracy, and factors affecting time
of flight measurement are discussed.