Chapter 3 SPAN Operation
OEM7 SPAN Installation and Operation User Manual v14
97
The accuracy of the initial attitude of the system following the kinematic alignment varies and depends on the
dynamics of the vehicle. The attitude accuracy will converge to within specifications once some motion is
observed by the system. This transition can be observed by monitoring the INS Status field in the INS logs.
Dual Antenna Alignment
SPAN can also use heading information available from a NovAtel Dual Antenna ALIGN solution to rapidly per-
form an alignment. Refer to
on page 129 for details.
NVM Seeded Alignment
SPAN can use the alignment information from a previous power up to quickly perform an alignment. For inform-
ation about enabling and using an NVM Seeded Alignment, refer to
INS Seed / Fast INS Initialization
Manual Alignment
If the initial azimuth of the system is known, it can be entered manually using the
SETINITAZIMUTH
command.
Refer to the
OEM7 Commands and Logs Reference Manual
for more information about this command.
A manual alignment should be used only if the azimuth is accurately known.
3.4.2 INS Seed / Fast INS Initialization
The INS Seed functionality is an alignment method whereby INS alignment information from a previous powerup
can be injected into the system at startup to achieve an INS alignment very quickly. This is especially useful for
systems that previously required a kinematic alignment.
When INS Seed is enabled, alignment data is automatically saved when appropriate, with no specific action
required from the user. During subsequent power ups, the saved solution is compared to the current position of
the system, and if valid, the saved solution is used to immediately initialize the inertial filter, making it ready for
use.
Error model information is also saved with the seed data. Even if full alignment cannot be achieved, this inform-
ation will still be used to aid filter convergence, although another method of alignment will be required.
This feature is enabled via the
INSSEED
command. This command setting must be saved to NVM via the
SAVECONFIG
command to be used upon next system boot-up.
Criteria
For the INS seed functionality to be enabled, the
INSSEED ENABLE
command must be sent.
Saving
The following criteria must be met for valid alignment data to be saved into receiver NVM.
l
The INS solution status must be converged, as indicated by the INS solution convergence flag in the inertial
Extended Solution Status.
l
The system velocity is less than 0.2 m/s.
When these conditions are met, the required information is automatically saved to NVM. If these conditions
cease to be met, the saved alignment data is automatically discarded. If the alignment data is discarded, error
model information is automatically retained as appropriate.
Use at Boot-up
Upon boot, several checks are done to verify that any seed data existing in NVM is appropriate for use. These
checks require a GNSS position to be computed, so an NVM seed will never be injected prior to achieving a