Tritech International Ltd
Intelligent Gyro Compass
8.6
Checking iGC output on an Arcnet interface
Using Arcnet for integrating the iGC into existing Tritech sensor networks offers some significant
advantages over multi-path data communications methods. It does however follow that the complexity
of Arcnet based systems is greater than simple RS232 or RS485 point-to-point implementations.
Refer to the Arcnet settings descriptions in Appendix G or in Section 10 – Operation below for details
of the type of data packets being transmitted over the Arcnet interface and the addressing modes
used.
In almost all cases where Arcnet systems are implemented, Tritech will have been involved with the
initial network design and set-up / testing. It is therefore recommended that where problems occur,
Tritech help-desk be contacted in the first instance to assist with the problem diagnosis. It is also usual
that specific procedures and documentation will exist for the Arcnet implementation. If this data is not
to hand or cannot be found, Tritech should have a copy of the original system configuration notes,
settings and drawings.
8.7
iGC data Check procedures
Once the ‘live’ iGC data is received correctly via the telemetry interface with the Host, the validity of this
data should be checked.
8.7.1
Heading Checks
Heading data should be checked against a known good heading reference (e.g. surveyed Magnetic
North reference line or a calibrated gyrocompass). If comparing the iGC heading against a True North
seeking gyro (NSG), the appropriate corrections should be made to the NSG heading to convert it to a
Magnetic North reference prior to checking the iGC.
When the North reference is confirmed, rotate the Host platform that the iGC is mounted to through
360º heading and check the correlation with the reference gyrocompass or against cardinal compass
points.
If the data from the iGC is not satisfactory, following steps in Section 9 – Calibration below, may make
improvements.
It should be noted that attempting to check magnetic heading performance on a Steel hulled / decked
vessels or in close proximity to steel structures (e.g. bulwarks, handling system components etc.) may
produce results that are not ideal.
8.7.2
Pitch & Roll Checks
The output of Pitch and Roll should be checked either with the Host system on a known horizontal flat
surface or alternatively against a calibrated vertical reference unit. The iGC gives accurate Pitch and
Roll data over the range +/- 50º and beyond. Pitch angles that approach 90º however cause instability
with the heading output of the device. This is not a limitation with the iGC sensors, but with the
mathematical angle conversions used in generating the output data. If users require pitch angles to be
measured /-60º, please contact Tritech for an alternative firmware implementation that does
not suffer from this problem.
Note that only certain Industry Standard telegram formats include the Pitch and Roll data, so if this data
is not requested it cannot be checked.
Issue 2
0707-SOM-00004
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