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Navigation Sensors · 333
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 GPS1 and GPS2) 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. There are three different reason to display Lat/Lon values of
Position sensor in red colour and with additional text.
· Kalman filter has excluded the sensor from its estimated position. Additional text is "Excluded"
· Received position from position sensor is in another Datum as set to be received in ECDIS. Additional text is
"Datum"
· If position sensors have position discrepancy active. Additional text is "Discrepancy".
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.
The system generates an alarm "4038 Datum mismatch" (alarm numbers are from 4038..4043 depending of
position receiver), if output Datum of a selected Position sensor (status any other than Off) is changed from WGS84
to another Datum or if selected Position sensor does not send Datum message. Additional text "Datum" in red
appears. Lat/Lon values of Position sensor turns red. If the position sensor is used for system position also Kalman
filter and own ship position (Lat/Lon values and used Datum) are indicated in red colour. If output Datum of a
selected Position sensor is changed from no Datum message or another Datum to WGS84 and, if the user has used