A.Their bearing is almost constant，even when the true bearing of the contact changes appreciably
B.They always appear on a bearing of 90°from the true bearing of the contact
C.The indirect echoes usually appear in shadow sectors
D.When plotted，their movements are usually abnormal
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A.radio signals reflect from a solid surface
B.sound waves travel at a constant speed through water
C.radar signals travel at a constant speed through water
D.pressure increases with depth
A.Water temperature
B.Climatology data
C.Speed of advance
D.Depth contours
A.Soundings
B.Waypoints
C.Meteorological data
D.Radar targets
A.Radar targets
B.ARPA vectors
C.Hydrographic data
D.All of the above
A.beam
B.radar
C.light beacon
D.reflector
最新試題
Error may be introduced into a magnetic compass by（）.
The radar component that produces the synchronizing signal and triggers the indicator sweep is which of the following?（）.
A radar contact will remain stationary on a relative motion radar display only when it is（）.
An ECDIS is required to display which information?（）
A barometer showing falling pressure indicates the approach of a（）.
The number of pulses of energy transmitted per second is call the（）.
An ECDIS is required to display which information?（）
（）the canal transit，the radar was operating.
Gyrocompass repeaters reproduce the indications of the master gyrocompass. They are（）.
Compass deviation is caused by（）.