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Real Time Positioning
The Need
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Construction operations involve location and
positioning elements in the field. These activities are typically performed by surveyors
and inspectors using traditional equipment such as theodolites, levels, and chains or
tapes. These traditional methods are laborious, time consuming, expensive and open to
errors when the data is gathered, transcribed and processed.
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Transmitters

Receivers

Space Station Software
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The Technology
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There are two primary components to the
system; transmitters and receivers. The system requires a minimum of two transmitters.
Each transmitter is set on a tripod with a front plate such that light can be scattered
about the site. A battery is used to power the unit, and each 12 volt battery will operate
a transmitter for 30 hours. The system can also be directly wired to a standard outlet
with the addition of an AC to DC converter. The set
up of the transmitters can be very quick and imprecise. The transmitters can be set up at
unknown points with the face plate generally aimed at the site. This can be thought of as
setting up a spotlight which is generally aimed at the site to be illuminated. However,
the energy source is infra-red which will allow only receivers to "see' the
"light". The site would require several known points to be established within
the area of the site to be used to back-calculate the position of the transmitters.
The receiver is comprised of a computer and screen, two
optical lenses mounted on a pole, a battery which is mounted on the pole, and a data entry
retrieval system. The two optical lenses form a line. The position of the lenses and the
known geometry of the pole allow the point position definition to be projected to the end
of the pole. Therefore, the position of any point that the user touches with the device is
accurately and "instantly" captured. Note that the position of the pole does not
change if the pole is slanted, rotated, upside down or sideways. The system can be
directly linked to CAD and the receiver becomes a three dimensional cursor within the CAD
environment. |
The Benefits
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The system allows multiple users to work at
the same time once the system is set up. These users can include surveyors, craftpeople,
and equipment operators each of whom is working concurrently and using the positioning
system to capture accurate real-time position information about the work environment. The
various users work from the same set of transmitters and can determine their position if
they can "see" any two transmitters. If the system is connected to CAD, it will
provide a real-time link between the physical and virtual design worlds. The system will work indoors, outdoors, under obstacles, in urban
environments, under water, on land, in the dark and in space. Also it is not affected by
changes in temperature or humidity nor by human sighting error. This greatly reduces human
error prevalent in current measurement techniques. In other words the implementation of
this system can result in higher productivity, better quality, less rework and improved
safety. |
Status
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A first system has been developed and
commercialized. Ongoing research and development will focus on the improvement of its
primary capabilities. The system currently provides 1:10,000 accuracies, 5 updates per
second, and has a working range of 130 meters. The next generation is expected to be of
millimeter accuracy over 200 meters with a 10 to 20 Hz data rate. Longer and higher rates
are anticipated. It is expected that the system will
work in many markets alongside current measurement equipment as an added tool in the
overall measurement toolkit. These other market segments include: measurement for object
placement and as-built creation, control of equipment, robotics or remotely operated
vehicle control and, modeling of surfaces. |
Barriers
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The primary limitation of the system is the
distance achieved. This can be partially negated by adding cascading areas of control.
This will allow individuals to move from one part of a large site to another. Continuity
of measurement can be established. As sensor and laser technology matures in areas of
visible light and other light frequencies, distance will increase. |
Points of Contact
- Beliveau, Yvan., Civil Engineering Dept., Virginia Tech,
Blacksburg, VA 24061-0105.
- Spatial Positioning Systems, Inc., Technology Center, 1700
Kraft Drive, Suite 1200, Blacksburg, VA 24060-6345. Phone: (540) 552-0010, Fax: (540)
552-0011
References
Beliveau, Yvan., "Real-Time Position Measurement:
Odyssey TM," Equipment Resource Management, pp. 203-208.
Disclaimer Statement
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Neither the Construction
Industry Institute nor Purdue University in any way endorses this
technology or represents
that the information presented can be relied upon without further investigation. |
IRA03
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| Last Modified: Saturday, 24-Jun-00 09:49:48 EST |
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