Time Constants - Simrad HS60 User Manual

HS60-s gyro aiding
The gyro aiding accurately smoothes the heading output and the
rate of turn. It provides an accurate substitute heading for a short
period depending on the roll and pitch of the vessel, ideally seeing
the system through to reacquisition. The gyro provides an alternate
source of heading, accurate to within 1º per minute for up to three
minutes, in times of GPS loss for either antenna. If the outage lasts
longer than three minutes, the gyro will have drifted too far and the
HS60 begins outputting null fields in the heading output messages.
There is no user control over the timeout period of the gyro.
Calibration, which is set at the factory, is required for the gyro to
remove latency from the heading solution as well as provide backup
heading when GPS is blocked. The receiver will calibrate itself after
running for a while but it may be important to follow the manual
calibration instructions if you want to guarantee performance
quickly after powering up the receiver.
With the gyro enabled, the gyro is also used to update the post
HTAU smoothed heading output from the GPS heading computa-
tion. This means that if the HTAU value is increased while gyro aiding
is enabled, there will be no lag in heading output due to vehicle
maneuvers. SIMRAD' GPS Technical Reference includes information
on setting an appropriate HTAU value for the application.

Time constants

The HS60 incorporates user-configurable time constants that can
provide a degree of smoothing to the heading, pitch, rate of turn
(ROT), course over ground (COG), and speed measurements. You
can adjust these parameters depending on the expected dynamics
of the vessel. For example, increasing the time is reasonable if the
vessel is very large and is not able to turn quickly or would not pitch
quickly. The resulting values would have reduced "noise, " resulting
in consistent values with time. However, if the vessel is quick and
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Operation | HS60 GPS Compass User Guide