Simrad SIMRAD HS50 manual Operation, Height aided GPS position

OPERATING INSTRUCTIONS

4.5Operation

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 between +/- 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.

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