Novatel NEXAGON CPT7, User Manual

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Chapter 4 SPAN Operation
CPT7 and CPT7700 Installation and Operation User Manual v12 88
Bit 31-29
Values 1
Hex Value NVM Seed Type
000 0x00 NVM Seed Inactive
001 0x01 Seed stored in NVM is invalid
010 0x02 NVM Seed failed validation check
011 0x03 NVM Seed is pending validation (awaiting GNSS)
100 0x04 NVM Seed Injected (includes error model data)
101 0x05 NVM Seed data ignored due to a user-commanded filter reset or configuration change
110 0x06 NVM Seed error model data injected
Table 12: NVM Seed Indication
4.4.3 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 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 filter decreases in its system accuracy, the INS Status field changes to INS_HIGH_
VARIANCE. When the accuracy converges again, the INS status continues as INS_SOLUTION_GOOD.
4.4.4 Data Collection
The INS solution is available in the INS-specific logs with either a standard or short header. Other parameters
are available in the logs shown in
Table 13: Solution Parameters below:
Parameter Logs
Position
INSPOS or INSPOSS
INSPVA or INSPVAS
INSPOSX or INSPVAX
Velocity
INSVEL or INSVELS
INSSPD or INSSPDS
INSPVA or INSPVAS
INSVELX or INSPVAX
Attitude
INSATT or INSATTS
INSPVA or INSPVAS
INSATTX or INSPVAX
Solution Uncertainty INSSTDEV or INSSTDEVS
Table 13: Solution Parameters
1The values from left to right are Bit 31, Bit 30 and Bit 29.