Navigation Sensors •
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Sheet "POSITION"
To select between
Speed/Course, Position or
Other sheets to be opened
either press button
or go by cursor above
Speed/Course, Position or
Other text and press SELECT
The field of a position sensor contains a label (here DGPS, GLL+ZDA) which indicates the name of the sensor; a
status (primary/secondary/off) which indicates, if the sensor is included or not; position in conning position and
local datum; speed and course which has (mag) if the course is referenced to magnetic north. A DGPS position
sensor has additional text Diff, if differential signal is in use. If the position is displayed in red colour, then Kalman
filter has excluded that sensor from its estimated position.
Position sensors have priority, which is indicated using sensors as primary and as secondary positioning source.
Only one sensor can be primary while the others can be secondary or off. After off-state a position sensor is changed
to secondary-state. After secondary-state a position sensor is changed to primary-state and if there was already a
position sensor with primary-state it will be changed automatically to secondary-state. When the position source is
changed based on priorities and signal validity to another position source, then you get alarm "2009 Position source
change". Note that alarm 2009 is active only without Kalman Filter because the filter has his own process to
calculate estimated position and in that process priority given by primary and secondary is not used.
If a DGPS selected as primary or secondary, changes its status from "no Diff" to "Diff" or from "Diff " to "no Diff"
the system generates alarm “4027 DGPS pos. Source change” (alarm numbers are from 4027..4032 depending of
position receiver).
Pri no alarm and Sec no alarm can be used with DGPS if you want disable alarm "4027 DGPS pos. source
change". These selection are intended for area where the differential coverage is fading. One example is if you sail
along coastline but so far away that the differential signal changes its status very often.
Enable chart align:
If selected, user is able to do a chart alignment by using CHART ALIGN button.
Alignment:
Alignment is selected automatically if user has defined position offset by CHART ALIGN push button. The offset
values are given in Nautical Miles and degrees. If position alignment is used then user is reminded of it every 30
minutes by Alarm "2011 ChartAlign: over 30 min".
Dead reckoning:
The system select automatically Dead reckoning, if there are no valid and selected position sources and if there are
valid and selected speed and course sources. If system has selected Dead reckoning, then the user can enter a new
position for the ship in the LAT. and LON fields.
Kalman filter:
If selected, Kalman filter calculates the estimate of position using simultaneously all valid and selected position,
speed and course sensors. To read more information about Kalman Filter, see "Filter Operation" on page 306.
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