Declination value, Pitch and roll – PNI TCM 2.6 User Manual
Page 20
PNI Sensor Corporation
DOC#1009269 r11
TCM2.5 & TCM2.6 User Manual
Page 20 of 49
The TCM2.5/2.6 can calibrate for any environment that creates a magnetic field that
does not exceed the dynamic range of its magnetometers.
Declination Value
Declination, also called magnetic variation, is the difference between true and magnetic north,
relative to a point on the earth. It is measured in degrees east or west of true north. Correcting for
declination is accomplished by storing the correct declination angle, and then changing the heading
reference from magnetic north to true north. Declination angles vary throughout the world, and
change very slowly over time. For the greatest possible accuracy, go to the National Geophysical
Data Center web page below to get the declination angle based on your latitude and longitude:
Pitch and Roll
The TCM2.5/2.6 uses accelerometers to measure the orientation of the compass with respect to
gravity. Since the compass also measures the complete magnetic field, the TCM2.5/2.6 can
correct for the tilt of the compass to provide an accurate heading.
The TCM2.5/2.6 utilizes Euler angles as the method for determining accurate orientation. This
method is the same used in aircraft orientation where the outputs are Heading (Yaw), Pitch and Roll.
When using Euler angles pitch and roll are defined as the angle rotated around an axis through the
center of the fuselage; pitch is rotation around an axis through the center of the wings. These two
rotations are independent of each other since the rotation axes rotate with the plane body.
For the TCM2.5/2.6 a positive pitch is when the front edge of the board is rotated upward and a
positive roll is when the right edge of the board is rotated downward.
Figure 3: TCM2.5 Pitch & Roll Axes
Figure 4: TCM2.6 Pitch & Roll Axes