Furuno FEA-2107 Operator's Manual page 339

Position page
The field of a position sensor contains a label (here
FURUNO and MX 200) which indicates the name of
the sensor; a status (primary/secondary/off) which
indicates if the sensor is used or not; position at 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. Latitude and longitude
values will appear in red and with additional text in the
following conditions:
•
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 the ECDIS.
Additional text is "Datum".
•
If position sensors have position discrepancy
active. Additional text is "Discrepancy".
Position sensors have priority, which is indicated as "primary" or "secondary". Only one sensor can be primary
while the others can be secondary or off. If a position sensor is changed from secondary to primary state and another
position sensor was chosen as primary, then that sensor previously selected to primary state is then automatically
selected to secondary state. When the position source is changed based on priorities and signal validity to another
position source, then you get the alarm "2009 Position source change". Note that alarm 2009 is active only when the
Kalman filter is off 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 is chosen as primary or secondary, and its status changes from "no Diff" to "Diff" or from "Diff " to "no
Diff" the system generates the alarm "4027 DGPS pos. Source change" (alarm numbers are from 4027 to 4032
depending on position receiver).
"Pri no alarm" and "Sec no alarm" can be chosen from the DPGS box if you want to disable the alarm "4027 DGPS
pos. source change". These selections are intended for the area where the differential coverage is fading. One
example is if you sail along coastline but you are so far away that the differential signal changes its status very often.
The system generates the alarm "4038 Datum mismatch" (alarm numbers are from 4038 to 4043 depending on the
position receiver) if output datum of a chosen position sensor (status other than Off) is changed from WGS-84 to
another datum or if chosen position sensor does not send datum message. Additional text "datum" appears, in red.
Further, lat/lon values for the position sensor turn red. If the position sensor is also used for system position, Kalman
filter and own ship position (Lat/Lon values and datum used) are indicated in red. If output datum of a chosen
position sensor is changed from no datum message or another datum to WGS-84 and the user has used the selection
Primary or Secondary, then the system generates the alarm "4044 Datum change" (alarm numbers are from 4044 to
4049 depending on position receiver).
Note: The ability to check datum of position is a relatively new feature for position receivers. It was introduced in
standard IEC 61162-1 Ed2, published in July 2000. Only EPFS (for example GPS or DGPS) which has "IEC 61162-
1 Ed 2 (2000-7)" indicated in their type approval certificate can support the ECDIS to detect datum mismatch.
The system generates the alarm "2007 Position discrepancy" if there is discrepancy in position. Together with this
alarm, the system shows the text "Discrepancy" in red in the Position page for a position sensor which has position
discrepancy active.
19. Navigation Sensors
19-3