航海学3期末考试简答题答案.doc

1,Gnomonic chart can be used to design a passage plan of ocean route. Please describe the steps which should be followed when use a gnomonic chart to design a passage plan of ocean route. ①Easy method but is not very exact ②Any great circle appears as a straight line. ③Consulting NP 131, choose corresponding Gnomonic charts. ④Draw a straight line connecting the point of departure and the destination on the chart. ⑤Inspect it to see that it passes clear of all dangers to navigation. ⑥If this requirement is met, the courses are then transferred to a Mercator chart by selecting a number of points along the great circle, determining their latitude and longitude and plotting these points on the Mercator chart. ⑦These points are then connected by straight lines to represent the rhumb line courses to be steered. 2，Gnomonic chart can be used to design a passage plan of ocean route. Please describe the steps which should be followed when use a gnomonic chart to design a passage plan of ocean composite route. ①Refer to relative navigation publications, determine the reasonable limiting latitude φL. ②From the departure A and destination B make the straight lines AM and BN tangent to the limiting latitude, and they are two great circle routes, the line between the two points of tangency M, N is limiting parallel track. ③Determine every rhumb line’s course and distance in the two great circle tracks. ④The course of parallel route course is 090° or 270 °, the distance could be measured in navigational chart. ⑤Make a table using the every rhumb line course and distance for next voyage. 3，The factors to be considered for ocean route choice. ①Meteorological conditions②State of the sea③Obstructions④Fixing and navigable water area conditions⑤Own ship conditions⑥Navigation regulations 4，The notes should be covered during ocean navigation. ①Do not ignore Dead reckoning②Use any resource to fix position③Note the safety problem when approaching shore④Receive and analyze forecast and we