JRC JMA-5212-4, User Manual

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5.2.6 Reference Target (Reference)
This equipment can calculate and display the speed of own ship by tracking a target whose position is fixed
with respect to the ground and by setting this target as a reference target.
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The reference target function is to be used if the own ship's
speed cannot be displayed normally due to trouble such as a
speed sensor malfunction. Do not use the reference target
function except in emergencies.
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If the speed or course of the own ship is changed or a new
reference target is set, the displayed speed may take 3 minutes
or more to reach the specified speed after the speed / course
change or the setting.
Even after 3 minutes or more has passed, the speed may differ
from the specified speed depending on the tracking condition.
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If a large radar echo such as a land target is set as a reference
target, the vectors of the speed and other tracking targets will
not be displayed correctly and may cause an accident.
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If a sailing ship is set as a reference target, the vectors of the
speed and other tracking targets will not be displayed correctly
and may cause an accident.
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If the REF. is selected for the speed sensor, the AIS function
cannot be turned on.
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If the reference target is lost or the target tracking function is
stopped, the speed sensor is placed in manual mode MAN .
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The loss of a reference target may have a major impact on the
accuracy of the results for true speed and true course of the
target and that own speed will be degraded.
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The reference targets are only used for the calculation of true
speed.
Attention