
3DM-GX4
™
-45
™
Inertial Navigation System
User Manual
Performance Optimization
41
diverge. Position and velocity errors will grow exponentially with measured acceleration error,
and attitude errors will grow linearly with estimated bias error. Monitoring uncertainty metrics
during GPS outage conditions will provide an indication of the reading reliability.
5.8
GPS Antenna Offset
GPS antenna offset is the distance of the antenna for the GPS receiver in the 3DM-GX4-45
™
.
This offset effects the accuracy of the GPS position readings. The MIP Monitor allows entry of
the offset in the Settings > Device > Estimation Filter > Mounting > Antenna Offset (
Figure 29 -
GPS Antenna Offset
).
For the best possible position accuracy, the GPS antenna offset should be defined to the
highest degree possible, preferably down to the centimeter or millimeter range. Inaccuracies
become non-negligible at 2 to 3 centimeters. The user should strive to minimize this distance as
large offsets (10s of meters or more) will result in position oscillation due to small orientation
inaccuracies. For example, a 1 degree error in attitude with a 10 meter antenna offset would
result in a position error of approximately 0.17 meters. If the offset was only 1 meter, the
position error would be 1.7 cm.
Figure 29 -
GPS Antenna Offset