Chapter 4 SMART7 with SPAN Operation
SMART7 Installation and Operation User Manual v6
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4.3 SPAN Translations and Rotations
A SPAN system combines GNSS and INS into a single system. In a GNSS system, the position is reported rel-
ative to the phase center of the GNSS antenna. In an INS system, the position, velocity and attitude data is
reported relative to the center of navigation of the IMU. For a SPAN system to provide a combined GNSS+INS
position, velocity and attitude, it must know where the GNSS antenna is positioned relative to the IMU.
The orientation of the IMU relative to the forward direction of the vehicle is also needed to convert the velocity
and attitude changes sensed by the IMU into the actual motion of the vehicle.
If the SPAN system incorporates other devices, the SPAN system also needs to know the location and ori-
entation of these additional devices relative to the IMU.
4.3.1 Translational Offsets
The three dimensional distances between the IMU and other SPAN components are called translational offsets.
The translational offsets are measured in three directions, X axis, Y axis and Z axis, typically relative to the IMU
Body frame. Translational offsets can also be entered relative to the Vehicle frame.
The X, Y and Z axes of the IMU Body frame are indicated on the SMART7 mechanical drawings. See
SMART7 Mechanical Specifications
The translational offsets from the IMU to the GNSS antenna are required for all SPAN systems. Since the IMU
and GNSS antenna are inside the SMART7 enclosure, the IMU to antenna offset is configured at the factory. No
additional translational offset configuration is needed on the SMART7, unless there are additional SPAN system
components that require an offset.
Do not
use the SETINSTRANSLATION ANT1 command to change the IMU to primary antenna offset.
Changing this value from the factory default will impair SPAN system performance.
Some SPAN systems may have other sensors or devices integrated into the system for which the SPAN needs
translational offsets. For example, a second receiver and GNSS antenna in a SPAN ALIGN system. The offsets
to these additional sensors and devices are also entered using the
SETINSTRANSLATION
command.
Figure 19: ALIGN Translation Offset
on the next page shows an example of the translational offsets between a
SMART7-S and a SMART7 in an ALIGN configuration. In this example, the SMART7-S is mounted at rear left
corner of the tractor roof and the IMU Body Frame of the SMART7-S (indicated by the small arrows) has the Y
axis pointing in the direction of the vehicle motion and the z axis pointing up.
