Simrad HS50, Instruction Manual

Page: 49 / 63

OPERATING INSTRUCTIONS
20221081 / F
41
4.5 Operation
The HS50 will normally output signals on the serial lines
without any involvement from the user. However, the following
should be taken into consideration during operation:
Height aided GPS position
In periods with weak satellite geometry, the position can be
made more accurate by using height aiding function in the
General submenu. Refer General , page 28.
The height aiding improves the solution by using the knowledge
that a vessel at sea has only small short-term variations in height
caused by heave. The long-term variations caused by tide are
taken care of in the system. The height value used, as input to
the GPS solution is a low-pass filtered value of the measured
height.
A start value for the low-pass filter should be specified for use at
system start-up. The value to use is the height of the Sensor unit
above the WGS-84 ellipsoid when the sea level is at its mean
value. This height can be found in the primary
Navigation/POS
display, where the HGT value is the GPS height. Refer
Navigation/POS display , page 36. The value should be
monitored for some minutes, and the average value should be
used.
Note! The height difference between mean sea level and the WGS-84
ellipsoid can be significant. Values b/- 100 meters can
be encountered.
For normal operation, height aiding should be set to FILTER or
OFF . When FILTER or FIXED is selected, an initial height
has to be entered.
Height aiding is active only with input of differential GPS.