Source Of Position - Furuno FEA-2807 Operator's Manual

19.3

Source of Position

The figure below shows how the source for position is selected. The Kalman filter uses all position sensors that have
either primary or secondary as input for its calculation. DGPS and SYLEDIS position sensors are considered more
accurate than other position sensors.
The latitude and longitude position is shown at the upper right corner on the ECDIS display, and in the example
below the position source is DGPS. Other indications that may be displayed in the position area are as follows:
•
NO POSIT: Appears (in red) when no dead reckoning sensors are selected and valid.
•
DEAD REC: Shown (in red) when position source is dead reckoning.
•
DGPS, GPS: LORAN, DECCA or SYLEDIS: Name of position source.
•
LOST DGPS: Shown (in red) when the operator-selected DGPS device has lost the DGPS signal.
•
FIL LOST DGPS: Shown (in red) when the Kalman filter is in use and the operator-selected DGPS device has
lost the DGPS signal.
•
FILTER HIGH: Shown when the position source is the Kalman filter with high-precision position sensor.
•
FILTER: Shown when position source is the Kalman filter without high-precision position sensor.
•
BAD FILTER: Shown (in red) when position source is the Kalman filter and the filter has excluded at least one
of the selected sensors because of poor accuracy.
KALMAN filter
GPS in diff. mode
Not
selected or SYLEDIS
selected as
PRIMARY
Not selected
or no position
Selected and
No position
°
HDG 071.0
SPD (WT) 15.6 kn
SB (POSN) 0.0 kn
°
COG (POSN) 071.0
SOG (POSN) 15.6 kn
59°31.206'N
024°36.731'E
WGS 84
(POSN)
DGPS
(POSN)
(POSN)
If the system changes the source of position because of lost sensor data or the differential mode is changed on a
DPGS device, the system immediately generates the alert "409 Position source change". If the Kalman filter is used,
the system generates the alert "410 Filter: POSN source CHG" after a time out period of 90 sec.
If a selected DGPS sensor changes its operation mode and its status is primary or secondary, then the system
generates the alert "727 DGPS pos. source change" (727 for first sensor, 728 for second, etc.). These alerts are not
generated if the operator has selected Pri no alert or Sec no alert.
If source of position includes a position sensor that is in datum mismatch condition, the latitude, longitude and
selected datum are displayed in red.
Selected and position exist
Selected and position exist
GPS in diff. mode
or SYLEDIS
selected as
SECONDARY
Any other than
Not selected
GPS in diff. mode
or no position
or SYLEDIS
selected as
PRIMARY
Not selected
or no position
Selected and position exist
Selected and position exist
Any other than
Selected and
GPS in diff. mode
position exist
or SYLEDIS
selected as
SECONDARY
Not selected
or no position
Backup
Dead Reckoning
19. Navigation Sensors
Position
used by
the system
19-5