Dead Reckoning Function - Kongsberg Simrad SN90 Reference Manual

Simrad SN90 Reference Manual

Dead Reckoning function

The
Dead Reckoning
the actual position of the drifting fishing gear. For this function to operate, the SN90
system requires input from a speed log.
How to open
This function is opened from the
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.
Tip
To draw the track line use the settings on the
located in the
Display Options
the menu.
Display
The
Minute Markers
how far you have sailed in the last few minutes. The minute markers are shown as
small circles on the vessel's track line. The
menu.
Visual Objects
454
function is used to improve the position of the track line relative to
menu.
Setup
dialog box. The
function adds markers to the track line. These markers indicate
page. The
Track Line
dialog box is located on
Display Options
function is located on the
Minute Markers
page is
Track Line
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