A.Blind sectors
B.Sheltered area
C.Unseen area
D.Unscanable area
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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
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
最新試題
A barometer showing falling pressure indicates the approach of a（）.
The radar component that generates the radio-frequency energy in the form of short powerful pulses is which of the following?（）.
Deviation in a compass is caused by the（）.
The radar component that produces the synchronizing signal and triggers the indicator sweep is which of the following?（）.
Error may be introduced into a magnetic compass by（）.
You are using a radar in which your own ship is shown at the center，and the heading flash always points to 0°. If bearings are measured in relation to the flash，what type of bearings are produced?（）.
A radar contact will remain stationary on a relative motion radar display only when it is（）.
（）should be used during the poor visibility if the radar’s screen shows heavy sea returns.
AREAS WHICH CANNOT BE SCANNED BY THE RADAR OF THE VESSEL BECAUSE THEY ARE SHIELDED BY PARTS OF ITS SUPERSTRUCTURE，MASTS，ETC means（）.
Compass deviation is caused by（）.