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Position/Orientation Trackers
Position trackers are instrumentation that can sense
the position and/or orientation of objects with some defined volume.
Unlike global positioning systems (GPS) which have a virtually unlimited
working volume, long latency, low sampling rate, and course resolution,
AuSIM's position trackers feature resolution and accuracy in the millimeter
range and sampling at interactive rates.
No matter which position tracking technology or instrument is chosen,
AuSIM's tracking software,
AuTrakTM,
provides the highest performance data of any available.
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- Electro-magnetic
- Polhemus Liberty
- Polhemus Patriot
- Polhemus Fastrak 2
- Polhemus Isotrak 2
- Polhemus Long Ranger (extended range transmitter)
- Ascension Flock of Birds
- Ascension Extended Range Transmitter (ERT)
Electro-Magnetic (EM) trackers have the wonderful properties of
having no line-of-sight (LOS) issues and detecting objects in all attitudes.
The tracking volume is a hemisphere
with the performance inversely proportional to the radius.
Electro-magnetic trackers are very sensitive to environmental conditions.
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- Ultra-sonic
- Logitech Ultra-sonic head-tracker by Fakespace
- InterSense IS-900
- InterSense IS-600 head-tracker
Ultra-Sonic tracking technologies are inexpensive and
easily calibrated to environmental conditions.
Because of their relatively large wavelengths,
the precision and accuracy of ultrasonic systems is low to medium.
Ultra-sonic trackers have a characteristic conic working volume,
are line-of-sight dependent and
suffer from long latencies proportional to the transmitter-receiver radius.
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- Inertial
- InterSense InertiaCube 2
- InterSense InterTrax 2, InterTrax
- InterSense IS-300, IS-300 Pro, IS-600, IS-600 Mark2, IS-900
Inertial tracking technologies sense the motion of objects
and calculate relative position through a double integration of the motion.
Inertial systems are source-less (no transmitter or grounded reference),
and thus have an infinite working volume.
The precision and accuracy of inertial systems may be quite high,
but only relative to the original assumed position.
Inertial tracking technologies may sample at very high rates,
and thus feel very responsive.
Inertial trackers tend to accummulate error
through the double integration of the sensed motion.
The accummulated error is evident as "drift".
The drift in inertial position tracking is typically corrected
with an inexpensive absolute tracking technology such as ultrasonics.
The drift in inertial orientation tracking is typically corrected
by the constant gravitational pull of the earth's core and the
constant magnetic pull of the earth's poles.
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- Optical: Infra-Red, Laser, and Visible
Infrared (IR) tracking technologies are fast, inexpensive,
and can range greatly in precision and accuracy.
IR trackers have an inherent line-of-sight dependence and conic working volume,
and can be sensitive to environmental conditions.
However, IR technology is compatible with redundant sensing,
which may enhance precision, accuracy, and working volume,
as well as reduce LOS factors.
Laser scanning trackers use 2D sweeps of laser light to
illuminate an object.
Some trackers use the reflection and range-finding techniques
to derive 3D information.
However, these techniques do not work well in dynamic situations.
More robust laser trackers place detectors on the target.
Visible light optical trackers use computer vision technology
to recognize objects or beacons in the image.
Visible light optical trackers share many characteristics
with IR trackers, but are more susceptable to noise,
require more signal processing, and can potentially
leave the tracked object unencumbered.
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