Furuno FEA-2807 Operator's Manual page 392

24. Recording Functions
Basic operation
Coordinates of the aid to navigation can be entered into dialog boxes or they can be selected graphically on the
chart:
• S57: Click on a charted object (beacon, light, buoy etc.). Description of the object appears above coordinate
boxes.
• ARCS: Click anywhere in the chart.
Default values for bearing and range are approximated from ship's current position information. The time of
observation is stopped when the object is selected.
Click the Add button to include the observation in the fix computation. The counter shows "new/1", and a second
observation may be entered. The word "new" indicates that the observation currently displayed is not yet included in
the fix computation, and it appears as a dashed line or ring on the chart. The added observations can be edited or
deleted after selecting them in the counter.
When at least two measurements are entered, the EP or fix is computed and the coordinates are shown in the top part
of the dialog, and a position symbol appears on the chart. In the case of an EP, the letters "EP" are shown on the
right side of the coordinates. If a valid position estimate cannot be obtained, a message is displayed under the
coordinates. This may happen, for example, if the lines / circles have multiple crossings that are far apart, or if two
lines are nearly parallel or don't intersect at all. The accuracy limit (estimated standard error) is 1.0 NM.
If the estimate is valid, the Record button can be clicked to record the current position estimate in the voyage log.
Discrepancy between LOP result and ship position is also recorded in the log. (This information may be viewed by
Info query on the position event symbol on the chart – which is displayed if position event display is on in chart
display settings.) If dead reckoning is active, the Use for DR button is visible and clicking it will make the LOP
position a new starting point for DR.
Time transfer
If the observations are not simultaneous, they should be transferred to a common time. Transferring is based on dead
reckoning of ship movement. If a position line (or ring) is transferred, the letters TPL are shown beside its
timestamp on the chart. The method of transfer may be selected in the bottom of the dialog. "Transfer to latest"
transfers the measurements as if they were all made at the time of the newest measurement. "Continuous transfer"
transfers all measurements to real time. "Transfer off" can be used to check where the measurement origins are. The
position estimate and the record function follow the same logic, which means that "Transfer off" shows a position
that has no relevance and "Transfer to latest" sends an old position to the voyage log (timestamp in the log does not
match the position).
Timeouts
The observations cannot be used long after they were made because dead reckoning is inaccurate.
•
One minute after the latest measurement it is labeled as a "DR" (dead reckoned position)
•
Computed position times out in 5 minutes after the latest measurement.
•
An observation times out in 10 minutes, after which it disappears without any notice to the user.
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