ProNav Norway – a
Company
page 43
Rev.2
10.02.2020
Time Constants
Overview
The V200n 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.
If the vessel is quick and nimble, increasing this value can create a lag in
measurements.
If you are unsure on how to set this value, it is best to be conservative
and leave it at the default setting.
Note:
For heading and rate of turn there is no lag once the sensor is
calibrated and enabled.
Formulas for determining the level of smoothing are located in the
Hemisphere GNSS Technical Reference Manual
. If you are unsure how to
set this value, it is best to be conservative and leave the default setting.
Heading
Use either MSGID 0x0028 (NMEA 2000) or the $JATT,HTAU command
(using the PocketMax Terminal window) to adjust the level of
responsiveness of the true heading measurement. The default value of
this constant is 0.1 seconds of smoothing when gyro-aid is enabled.
By disabling gyro-aid, the equivalent default value of the heading time
constant should be 0.5 seconds of smoothing. This is not automatic, and
therefore it must be manually entered.
Note:
Increasing the time constant increases the level of heading
smoothing and increases lag (with gyro-aid disabled).
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