Chapter 4 SPAN Operation
CPT7 and CPT7700 Installation and Operation User Manual v12
83
Body to Vehicle Frame Rotation Calibration Routine
on page 91 or
Multi-Line Body to Vehicle Frame Rotation
on page 91 for more information.
These parameters are estimated in the background when the system is fully converged, however it is always
better to have this measured as precisely as possible before mission critical data is collected.
Since slight variations in alignment can be introduced when the CPT7 is remounted, a Body to Vehicle
Frame calibration should be performed each time the device is remounted.
An accurate RBV is especially important if the position is being transferred to a user offset.
4.4 Real-Time Operation
SPAN operates through the OEM7 command and log interface. Refer to the
log and command details.
Real-time operation notes:
l
By default, raw IMU data will begin to output as soon as the IMU is connected. However an initial position is
required to begin the INS alignment process. This position is typically set by GNSS. The GNSS position will
not be used until the FINESTEERING time status is reached. This requires a GNSS antenna connected
with a clear view of the sky. See
System Start-Up and Alignment Techniques
on the next page for more
details.
l
The inertial solution is computed separately from the GNSS solution. The GNSS solution is available from
the SPAN system through the GNSS-specific logs, even without SPAN running. The integrated
GNSS+INS solution is available through special INS logs documented in INS Logs in the
Commands and Logs Reference Manual
l
The IMU raw data is available at the maximum rate of output of the IMU. Because of this high data rate, a
shorter header format was created. These shorter header logs are defined with an S (RAWIMUSXB rather
than RAWIMUXB). We recommend you use these logs instead of the standard header logs to save
throughput on the COM port.
Status of the inertial solution can be monitored using the inertial status field in the INS logs, see
Binary
ASCII
Description
0
INS_INACTIVE
IMU logs are not yet present or the alignment routine is not yet initialized. INS
state is inactive.
1
INS_ALIGNING
INS is in alignment mode.
2
INS_HIGH_
VARIANCE
The INS solution uncertainty contains outliers and the solution may be outside
specifications. The solution is still valid but you should monitor the solution
uncertainty in the
INSSTDEV
log. It may be encountered during times when
GNSS is absent or poor.
Table 11: Inertial Solution Status
