Chapter 3 SPAN OperationOEM7 SPAN Installation and Operation User Manual v14 97The accuracy of the initial attitude of the system following the kinematic alignment varies and depends on thedynamics of the vehicle. The attitude accuracy will converge to within specifications once some motion isobserved by the system. This transition can be observed by monitoring the INS Status field in the INS logs.Dual Antenna AlignmentSPAN can also use heading information available from a NovAtel Dual Antenna ALIGN solution to rapidly per-form an alignment. Refer to SPAN with Dual Antenna on page 129 for details.NVM Seeded AlignmentSPAN 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 below.Manual AlignmentIf 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 InitializationThe INS Seed functionality is an alignment method whereby INS alignment information from a previous powerupcan be injected into the system at startup to achieve an INS alignment very quickly. This is especially useful forsystems that previously required a kinematic alignment.When INS Seed is enabled, alignment data is automatically saved when appropriate, with no specific actionrequired from the user. During subsequent power ups, the saved solution is compared to the current position ofthe system, and if valid, the saved solution is used to immediately initialize the inertial filter, making it ready foruse.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 theSAVECONFIG command to be used upon next system boot-up.CriteriaFor the INS seed functionality to be enabled, the INSSEED ENABLE command must be sent.SavingThe 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 inertialExtended 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 conditionscease to be met, the saved alignment data is automatically discarded. If the alignment data is discarded, errormodel information is automatically retained as appropriate.Use at Boot-upUpon boot, several checks are done to verify that any seed data existing in NVM is appropriate for use. Thesechecks require a GNSS position to be computed, so an NVM seed will never be injected prior to achieving a
