How To Input Your Ship's Speed; Echo-Referenced Speed Input - Furuno FCR-21x9-BB Operator's Manual

3. TARGET TRACKING (TT)
3.3

How to Input Your Ship's Speed

The TT requires own ship's speed and heading data. The speed can be STW, SOG,
or echo-referenced speed (based on 3 max. stationary objects) taken from this radar.
Manual input is also possible.
For automatic or manual speed input, see section 1.14. For echo-referenced speed
input see the next section.
3.3.1

Echo-referenced speed input

The use of echo-referenced speed is recommended when:
• The speed log is not operating properly or not connected to the radar.
• The vessel has no device that can measure ship's leeward movement (Doppler so-
nar, speed log, etc.) when leeward movement cannot be disregarded.
If you select echo-referenced speed, the TT calculates own ship's speed relative to a
fixed reference target. The number of targets may be 1, 2 or 3. They appear as tracked
targets, each denoted with a small circle. When a plural number of objects are select-
ed, the mean value is used.
Note: This feature is not available when the AIS is active.
1. RIght-click the display area to show the context-sensitive menu then select [REF
Mark].
2. Select a small fixed island or any radar prominent point located at 0.1 to 24 nm
from own ship.
3. Use the trackball to put the cursor (+) on the target selected at step 2.
4. Push the left button to insert the reference mark.
5. Repeat steps 2-4 to continue entering reference marks. Three may be entered.
6. Right click the Sensor information box then choose [Select Sensor] and [Setting].
Open the [SPD] page and put a checkmark at [Reference SPD]. Click the [OK]
button to finish.
Notes on speed input by reference target
• Reference targets are only used for the calculation of true speed.
• Do not use reference target generated true speed to calculate relative speed. Rel-
ative speed data is not accurate because response to speed change is slow, ham-
pering the TT's ability to accurately judge the possibility of collision.
• Select a stationary target as a reference target to calculate own ship speed as
ground tracking speed. Do not choose a moving target as a reference target. A mov-
ing target produces error in the vector for TT and AIS, which results in wrong colli-
sion avoidance information. Further, an unstable stationary target produces
inaccurate speed data and the target itself may become lost.
• When a reference target is lost or goes out of the acquisition range, the reference
target mark flashes and the Alert 528 "REF Target Lost" appears in the [Alert] box.
3-2
Changes to in three minutes
R01
R01