A great circle track provides the maximum saving in distance on（）.

单项选择题A gnomonic projection is based on a(n)（）.

A.plane tangent at one point
B.cylinder tangent at the equator
C.cone tangent at one parallel
D.infinite series of cones tangent at selected parallels

单项选择题（）refers to the angle between true North and the heading line of the ship.

A.True position
B.True meridian
C.True course
D.True bearing

单项选择题（）is the distance east or west measured in degrees，minutes and seconds of arc on the equator between the prime meridian and the meridian passing through the place.

A.Longitude
B.Latitude
C.Height
D.Bearing