USER MANUAL
URM18PH392 Rev A. May 2020 Page 69 of 86
Elevation Coordinate of orientation tracking in the vertical plane where an increase in the angle is
upward from the horizontal. Elevation is a rotation around the Y (horizontal) axis, where
an increase in the angle is clockwise when viewed in the positive direction along this
axis. Note, in Polhemus’ default frame of reference, the +Y axis points to the right, with
+X pointing forward and +Z pointing down. The term “pitch” is often substituted for
azimuth, especially in the context of flight.
EM Field Electromagnetic Field. An EM field is a combination of an electric field (created by
changes in voltage) and a magnetic field (created by flow of electric current).
Euler Angles See Orientation Angles.
Factory Defaults The values assigned to certain system variables by the factory. Stored in non-volatile
memory, they are used to reinitialize the variables if configuration information is lost.
Firmware Term used to describe the software programmed into VIPER™ non-volatile memory.
Frame of Reference Also called a reference frame. In 3 dimensions, 3+1 reference points are sufficient to
fully define a reference frame. Using Cartesian coordinates, a reference frame may be
defined with a reference point at the origin and a reference point at one unit distance
along each of the 3 coordinate axes. When a standard Polhemus Source serves as the
reference, the origin is at the EM center of the Source and the positive X, Y, and Z axes
extend forward, right, and down from the EM center.
Hemisphere The symmetry of the magnetic fields generated by the Source creates two mathematical
solutions to each set of Sensor data processed. Therefore, only half of the total spatial
sphere surrounding the Source is practically used at any one time without ambiguity in
the X, Y, Z measurements (usually sign flips). This half sphere is referred to as the
“current hemisphere.”
When configuring Hemisphere, the selected hemisphere is defined by a LOS (line-of-
sight) vector from the source through a point at the zenith of the hemisphere, and is
specified by the direction cosines of the chosen LOS vector. See also Hemisphere
Tracking and Auto-Hemisphere Tracking definitions. See Appendix B.
Hemisphere Tracking A feature in which the Polhemus tracker continuously modifies the operating
Hemisphere, allowing full tracking coverage around all sides of the Source. Note that the
Sensor must be in a known, valid Hemisphere before engaging Hemisphere Tracking.
Host Any modern computer device capable of supporting an RS-422 interface or the high
speed USB 2.0 interface and capable of bi-directional data transmission.
I/O latency The interval of time needed by the host computer to transfer data from the VIPER™
system into the host application.
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