System Start-Up And Alignment Techniques - Novatel SMART7 Installation And Operation Manual

SMART7 with SPAN Operation
Binary ASCII
WAITING_
10
AZIMUTH
INITIALIZING_
11
BIASES
MOTION_
12
DETECT

4.5.1 System Start-Up and Alignment Techniques

The system requires an initial position, velocity and attitude estimate to start the navigation fil-
ter. 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 com-
mand 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 system transitions to navigation mode.
9. The solution is refined using updates from GNSS. Once the system is operating within spe-
cifications and after some vehicle movement, the INS Status field changes to INS_
SOLUTION_GOOD. This indicates that the INS filter has successfully converged to within per-
formance specifications.
Kinematic Alignment
The kinematic or moving alignment is performed by estimating the heading from the GNSS velo-
city vector and injecting it into the SPAN filter as the initial system heading.
For the kinemtic alignment routine to work optimally, the course-over-ground azimuth must not
include any bias from the defined Vehicle Frame. (For example, a plane being blown in the wind
SMART7 Installation and Operation User Manual 0C
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.
The INS filter has determined the IMU orientation, received an initial
position and is conducting an initial IMU bias estimate.
Vehicle motion has been detected during the alignment procedure.
Description
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