Vector Sensor Reference Manual 26
Note - If you are unsure of the best value for this setting, it’s best to be conservative
and leave it at the default setting of 2.0 seconds when the gyro is on and at 0.5 seconds
when the gyro is off.
1.8.6.2 Pitch Time Constant
The pitch time constant allows you to adjust the level of responsiveness of the pitch measurement
provided in the $PSAT,HPR message. The default value of this constant is 0.5 seconds of
smoothing. Increasing the time constant will increase the level of pitch smoothing.
The following command is used to adjust the pitch time constant.
$JATT,PTAU,ptau<CR><LF>
Where ‘ptau’ is the new time constant that falls within the range of 0.0 to 3600.0 seconds.
Depending on the expected dynamics of the vessel, you may wish to adjust this parameter. For
instance, if the vessel is very large and is not able to pitch quickly, increasing this time is reasonable.
The resulting pitch would have reduced ‘noise’, resulting in consistent values with time. However,
artificially increasing this value such that it does not agree with a more dynamic vessel could create
a lag in the pitch measurement. A convenient formula for determining what the level of smoothing
follows. If you are unsure on how to set this value, it’s best to be conservative and leave it at the
default setting.
ptau (in seconds) = 10 / maximum rate of pitch (in °/s)
You may query the Vector PRO for the current pitch time constant by issuing the same command
without an argument.
$JATT,PTAU<CR><LF>
Note - If you are unsure of the best value for this setting, it’s best to be conservative
and leave it at the default setting of 0.5 seconds.
1.8.6.3 Heading Rate Time Constant
The heading rate time constant allows you to adjust the level of responsiveness of the rate of
heading change measurement provided in the $HEROT message. The default value of this
constant is 2.0 seconds of smoothing. Increasing the time constant will increase the level of
heading smoothing.
The following command is used to adjust the heading time constant.
$JATT,HRTAU,hrtau<CR><LF>
Where ‘hrtau’ is the new time constant that falls within the range of 0.0 to 3600.0 seconds.
Depending on the expected dynamics of the vessel, you may wish to adjust this parameter. For
instance, if the vessel is very large and is not able to turn quickly, increasing this time is reasonable.
The resulting heading would have reduced ‘noise’, resulting in consistent values with time.
However, artificially increasing this value such that it does not agree with a more dynamic vessel
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