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SPAN-CPT Operation Chapter 3
SPAN-CPT User Manual Rev 8 29
3.4.1.2 Manual Alignment
If the attitude of your vehicle (roll, pitch, azimuth) is known, enter the attitude information using the
SETINITATTITUDE command. Details of this command are in the SPAN on OEM6 Firmware Reference
Manual (OM-20000144).
3.4.1.3 Dual Antenna Alignment
SPAN can also use information available from a NovAtel Dual Antenna ALIGN
®
solution to perform an
alignment. Refer to Chapter 4, SPAN-CPT Dual-Antenna on page 37 for details.
3.4.2 Navigation Mode
Once the alignment routine has successfully completed, SPAN enters navigation mode.
SPAN computes the solution by accumulating velocity and rotation increments from the IMU to generate
position, velocity and attitude. SPAN models system errors by using a filter. The GNSS solution, phase
observations and automatic zero velocity updates (ZUPTs) provide updates to the filter. Peripheral
updates can also be supplied; wheel sensor for displacement updates or an external receiver for heading
updates.
Following the alignment, the attitude is coarsely defined, especially in heading. Vehicle dynamics,
specifically turns, stops and starts, allow the system to observe the heading error and allows the heading
accuracy to converge. The amount of dynamics required for filter convergence vary by the alignment
quality, IMU quality, and maneuvers performed. The INS Status field changes to INS_SOLUTION_GOOD
once convergence is complete. If the attitude accuracy decreases, the INS Status field changes to
INS_HIGH_VARIANCE. When the accuracy converges again, the INS status continues as
INS_SOLUTION_GOOD.
3.4.3 Vehicle to SPAN-CPT Frame Angular Offsets Calibration Routine
Kinematic fast alignment requires the angular offset between the vehicle and the SPAN-CPT frame is
known approximately. If the angles are simple (that is, a simple rotation about one axis), the values can
easily be entered manually through the VEHICLEBODYROTATION command. If the angular offset is more
complex (rotation is about 2 or 3 axis), then the calibration routine may provide a more accurate
estimation of the values.
The steps for the calibration routine are:
1. Apply power to the SPAN-CPT (see Appendix A, Technical Specifications on page 48).
2. Configure the SPAN-CPT (see SPAN IMU Configuration on page 25).
3. Ensure an accurate lever arm is entered into the system.
4. Allow the system to complete an alignment (see the System Start-Up and Alignment Techniques on
page 27).
5. Enable the vehicle to body calibration using the RVBCALIBRATE ENABLE command. See the SPAN
on OEM6 Firmware Reference Manual (OM-20000144).
6. Start to move the system under good GNSS conditions. Movement of the system under good GNSS
conditions is required for the observation of the angular offsets.
Vehicle speed must be greater than 5 m/s (18 km/hour) for the calibration to complete. Drive straight
on a level surface if possible.
7. When the solved angles are verified (after approximately 30 seconds), the calibration stops and the
VEHICLEBODYROTATION log provides the solved values. Log VEHICLEBODYROTATION using
the ONNEW trigger to monitor the progress of the calibration.