Chapter 3 SPAN Operation
OEM7 SPAN Installation and Operation User Manual v14
95
Binary
ASCII
Description
6
INS_
SOLUTION_
FREE
The INS filter is in navigation mode and the GNSS solution is suspected to be in
error.
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.
7
INS_
ALIGNMENT_
COMPLETE
The INS filter is in navigation mode, but not enough vehicle 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.
10
WAITING_
AZIMUTH
The INS filter has determined the IMU orientation, received an initial position and
completed initial bias estimates. Azimuth input (from vehicle motion, dual antenna or
command) is required for alignment.
11
INITIALIZING_
BIASES
The INS filter has determined the IMU orientation, received an initial position and is
conducting an initial IMU bias estimate.
12
MOTION_
DETECT
Vehicle motion has been detected during the alignment procedure.
3.4.1 System Start-Up and Alignment Techniques
The system requires an initial position, velocity and 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. The INS Status field changes from INS_INACTIVE through DETERMINING_ORIENTATION and
WAITING_INITIALPOS.
5. Once a GNSS position is available, an initial IMU bias estimate is conducted. During this period, the INS
Status field reports INITIALIZING_BIASES.
6. After the bias estimate is complete, the coarse alignment routing starts. Bias estimates will be refined and a
static alignment completed, if IMU quality allows. During this period the INS Status field reports INS_
ALIGNING.
7. If static coarse alignment is not possible or is locked out by command, the system will require an external
azimuth input, either from vehicle motion, dual antenna input or command input. While in this state the INS
Status field reports WAITING_AZIMUTH.
If vehicle movement is detected, any ongoing static coarse alignment will be reset, and the INS Status field
will report MOTION_DETECT.
8. After an alignment is completed, the INS Status field changes to INS_ALIGNMENT_COMPLETE. The