User Manual Part 2

IS-900 User Guide Page 154 of 159
drift and maintain stability, but not as an absolute measurement system. In this
mode system is much less susceptible to magnetic interference, but heading drift
will accumulate. If compass is off, no heading compensation is applied. Older
versions of tracker firmware supported only 0 and 1, which stood for ON or
OFF. Please use the new notation. This API will correctly interpret the settings.
InertiaCube
InertiaCube associated with this station. If no InertiaCube is assigned, this
number is -1. Otherwise, it is a positive number 1 to ISD_MAX_STATIONS.
Only relevant for IS-300 and IS-600 Series devices. For IS-900 systems, it is
always the same as the station number, for InterTrax and InertiaCube2 it’s
always 1.
Enhancement
In order to provide the best performance for a large range of various applications,
three levels of perceptual enhancement are available. None of the modes introduces
any additional latency. The InterTrax is restricted to Mode 2.
Mode 0 provides the best accuracy. The inertial tracker uses gyros to measure
angular rotation rates for computing the sensor’s orientation. To compensate for the
gyroscopic drift, depending on the configuration, the tracker may use
accelerometers, magnetometers or SoniDiscs to measure the actual physical
orientation of the sensor. That data is then used to compute the necessary
correction. In Mode 0 correction adjustments are made immediately, no jitter
reduction algorithms are used. This results in somewhat jumpy output (not
recommended for head tracking) but with lower RMS error. Use this mode for
accuracy testing or for any application that requires best accuracy.
Mode 1 provides accuracy similar to that of mode 0, with an addition of a jitter
reduction algorithm. This algorithm reduces the accuracy by only a small amount and
does not add any latency to the measurements. Mode 1 is recommended for
augmented reality applications (i.e. overlaying or mixing both virtual and real objects
in a visualization system.)
Mode 2 is recommended for use with HMD or other immersive applications. The
drift correction adjustments are made smoothly and only while the sensor is
moving, so as to be transparent to the user.
Sensitivity
This setting is only used when Perceptual Enhancement Level is set to 1 or 2. It
controls the minimum angular rotation rate picked up by the InertiaCube. Default
is level 3. Increasing sensitivity does not increase latency during normal
movements. It may, however, result in some small residual movements for a
couple of seconds after the sensor has stopped. If your application requires
sensitivity greater than maximum provided by this control, you must use
Perceptual Enhancement level 0. For InterTrax this value is fixed to default and
can’t be changed.