3DM-GX4
™
-45
™
Inertial Navigation System
User Manual
Sensor Measurements
27
4.3
Computed Outputs (Estimation Filter/PVA)
The computed outputs are measurements from the 3DM-GX4-45
™
IMU sensors and GPS
receiver that are processed through an Extended Kalman Filter (EKF) algorithm. Together they
produce high accuracy position, velocity, and attitude (PVA) outputs at high data rates. Refer to
Table 6 - Estimation Filter Outputs
for a complete list of outputs.
All computed outputs are determined with reference to the sensor frames (
see Sensor
Reference Frames on page 30
). Heading is the direction of travel derived from the GPS and
velocity or magnetometer readings. Position is the coordinate location of the sensor, and
velocity is the rate of change from that position. Attitude is an estimation of the sensor’s
orientation in space and is generated from the sensed acceleration and magnetic field vectors,
and gyroscope outputs. Attitude is reported as roll, pitch, and yaw. All output estimates
represent the orientation of the device relative to the local North, East, Down (NED) frame at a
particular point on the Earth’s surface.
In the MIP Monitor software there are user settable options for how the estimations are made.
These setting are available in the Settings > Device > EF (tab). The context sensitive Help
menus (accessed with the Help button) provides explanations of the settings when hovered
over (
Figure 18 - Estimation Filter Settings
).
Figure 18 -
Estimation Filter Settings