The navigator must be able to recognize various abnormal echoes and effects on the radarscope so as not to be confused by their presence.
INDIRECT (FALSE) ECHOES
Indirect or false echoes are caused by reflection of the main lobe of the radar beam off ship’s structures such as stacks and kingposts. When such reflection does occur, the echo will return from a legitimate radar contact to the antenna by the same indirect path. Consequently, the echo will appear on the PPI at the bearing of the reflecting surface. This indirect echo will appear on the PPI at the same range as the direct echo received , assuming that the additional distance by the indirect path is negligible.
Characteristics by which indirect echoes may be recognized are summarized as follows:
