Kongsberg Seapath 320, Installation Manual, Page: 81 / 152

Installation Manual
M300-62/rev.2 65
4.4.4.3 Heave configuration
When using real-time heave measurements, it is important to tune the heave parameters
(heave period and damping) to the vessel size and the motion characteristics for the
actual weather conditions. The default settings for filter mode heave period and
damping, have to be tuned for the actual vessel and weather conditions in order to
achieve optimum heave performance. Therefore, before a survey and/or during
operation check the heave performance of the Seapath and tune the heave parameters
until the best heave performance is achieved. An alternative is to select Automatic and
let Seapath automatically choose the best settings. The following should be considered
when selecting the different heave filter modes and parameters:
Filter mode:
Automatic . To be selected when the vessel is operating in various sea states or when
the average heave period is unknown.
General purpose . Is selected when an optimal heave amplitude is to be measured
and the heave phase is of no importance. This mode is typically selected when the
Seapath is to be used for measuring the heave height and period on oceanographic
buoys.
Hydrographic survey . To be selected when the heave phase and amplitude have to
be output correct in real time. This mode is typically selected when the heave output
signal from the Seapath is to be used for heave compensation of echo sounders and
offshore crane systems.
Period:
An expected average heave period has to be set to the heave filter. This period can be
determined by measuring the time between two wave-tops by using a watch.
The settling time for the heave measurements from power-on or after a turn will be
about 10 times the selected period, T
o
. By selecting an unnecessary long heave
period, the settling time will be slower than it has to. For vessels performing surveys
with frequent turns, the period should be set as low as possible to minimise the heave
settling time after turns.
Damping:
The heave damping factor is usually set to 0.7. Only for special occasions should this
parameter be changed. In operations with heave periods of more than 25 seconds, the
damping factor should be reduced to 0.6 in order to achieve correct phase
measurements. In operations with heave periods of less than 2 seconds, the damping
factor should be increased to 0.8.
For more details on selection of heave filter mode and parameters, see the User
Manual.
In order to select the heave configuration proceed as follows: