Novatel OM-20000122 user manual System Start-Up and Alignment Techniques, Ascii

SPAN-CPT Operation			Chapter 3
		Table 4: Inertial Solution Status
Binary	ASCII		Description
0	INS_INACTIVE		IMU logs are present, but the alignment routine has not started;
			INS is inactive.
1	INS_ALIGNING		INS is in alignment mode.
			The INS solution is still being computed but the azimuth solution
			uncertainty has exceed the threshold. The default threshold is 2
2	INS_HIGH_VARIANCE		degrees.a The solution is still valid but you should monitor the
			solution uncertainty in the INSCOV log. You may encounter this
			state during times when the GNSS, used to aid the INS, is
			absent.b
3	INS_SOLUTION_GOOD		The INS filter is in navigation mode and the INS solution is good.
			The INS filter is in navigation mode and the GNSS solution is
			suspected to be in error.
6	INS_SOLUTION_FREE		This may be due to multipath or limited satellite visibility. The
			inertial filter has rejected the GNSS position and is waiting for the
			solution quality to improve.
			The INS filter is in navigation mode, but not enough vehicle
7	INS_ALIGNMENT_COMPLETE		dynamics have been experienced for the system to be within
			specifications.
8	DETERMINING_ORIENTATION		INS is determining the IMU axis aligned with gravity.
9	WAITING_INITIALPOS		The INS filter has determined the IMU orientation and is awaiting
			an initial position estimate to begin the alignment process.

a.This value is configured using the INSTHRESHOLDS command. See the SPAN on OEM6 Firmware Reference Manual (OM-20000144) for more information.

b.See also question #5 in Appendix C, Frequently Asked Questions on page 56.

3.4.1System Start-Up and Alignment Techniques

The system requires an initial attitude estimate to start the navigation filter. This is called system alignment. On start-up the system has no position, velocity or attitude information. When the system is first powered up, the following sequence of events happens:

1.The first satellites are tracked and coarse time is solved.

2.Enough satellites are tracked to compute a position.

3.Receiver “fine time” is solved, meaning the time on board the receiver is accurate enough to begin timing IMU measurements.

4.Raw IMU measurements begin to be timed by the receiver and are available to the INS filter. They are also available in the RAWIMU, RAWIMUS, RAWIMUX, and RAWIMUSX logs. The INS Status field changes from INS_INACTIVE through DETERMINING_ORIENTATION and WAITING_INITIALPOS during this period.

5.The inertial alignment routine starts and the INS Status field reports INS_ALIGNING.

6.When the kinematic alignment is completed and the INS Status field changes to INS_ALIGNMENT_COMPLETE. The system transitions to navigation mode.

SPAN-CPT User Manual Rev 8 27