Kongsberg Simrad CS90, Reference Manual

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Related topics
Defining settings related to user preferences and individual customizing, page 156
Functions and dialog boxes, page 413
Setup menu; Functions and dialog boxes, page 447
Dead Reckoning function
The
Dead Reckoning
function is used to improve the position of the track line relative to the
actual position of the drifting fishing gear. For this function to operate, the CS90 system
requires input from a speed log.
How to open
This function is opened from the
Setup
menu.
Description
This is an "on/off" function. When switched “off”, the GPS is used to calculate the position
of your vessel. When “on”, the position is calculated based on the current speed and the
input from the course gyro.
In navigation, dead reckoning is the process of calculating current position of some
moving object by using a previously determined position, or fix, by using estimations
of speed, heading direction and course over elapsed time. [..] Dead reckoning is subject
to cumulative errors. Advances in navigational aids that give accurate information on
position, in particular satellite navigation using the Global Positioning System, have
made simple dead reckoning by humans obsolete for most purposes. However, inertial
navigation systems, which provide very accurate directional information, use dead
reckoning and are very widely applied. [..] In marine navigation a "dead" reckoning
plot generally does not take into account the effect of currents or wind.
Aboard ship a dead reckoning plot is considered important in evaluating position
information and planning the movement of the vessel.
https://en.wikipedia.org/wiki/Dead_reckoning (November 2020)
When dead reckoning is switched off, the vessel movement and track line are calculated
from the GPS data. These are relative to the bottom. When switched on, the inputs from the
gyro and speed log are used to positioning the vessel relative to the water.
Simrad CS90 Reference Manual