Invalid Heading; Reduced Heading Indication - Simrad HS52 Instruction Manual

20222360 / E

Invalid Heading

The possible problem can be one of the following:
•
The heading status will be invalid if there is no data from
the Sensor unit or no Sensor unit is connected to the
Processing unit. The system will always indicate invalid
heading for a short period of time at system reboot.
•
If the system looses GPS heading for a certain period of
time, the heading accuracy will slowly decrease. The
heading status will after 60 seconds become reduced, and
after 300 seconds be invalid. The reason for missing GPS
heading might be too few visible satellites, low geometry or
excessive multipath.
•
If the filter integrity check algorithm detects a large
mismatch between the GPS heading and the integrated
system filter, the heading status will be invalid, and the
heading filter will be reset.
If invalid heading, then proceed as follows:
• The Sensor unit is unable to see enough GPS satellites. Press
the NAV2/POS button until the Skyplot view appears.
Check that at least four satellites are listed in the Satellite
Skyplot, see Navigation/POS Display on page 46, and that
the PDOP value is less than 6. Check also the number of
common satellites seen by the two GPS antennas by pressing
the INFO button and looking at the value for Common sat.
in the advanced heading information display, se Info
Displays on page 46 . The number of common satellites has
to be three or higher to keep a heading. To find a new
heading after the loss of GPS heading at least four common
satellites with a reasonable geometry have to be present. If
one of the criteria's above is not fulfilled, the mounting
location of the Sensor unit may not be suitable or there may
be an obstruction between the Sensor unit and the GPS
satellites. Check the mounting location and consider moving
the vessel to another location or a relocation of the Sensor
unit according to the guidance described in chapter Location
of the Unit on page 12.
If it is still not working after checking the above items, consult
your nearest Simrad dealer for assistance.

Reduced Heading Indication

The reason for reduced heading can be one of the following:
• At system restart or at heading filter initialization there is a
certain filter initialization period where the heading accuracy
will be reduced.
MAINTENANCE
61