單項(xiàng)選擇題
A.the lines of force cross the equator on a 0°-180°alignment B.the quadrantal error is 0° C.there is no vertical component of the Earth's magnetic field D.the intercardinal headings have less than 1°
A.buoys close at hand B.fixed known objects on shore C.buoys at a distance D.All of the above
A.running fix B.fix C.estimated position D.assumed position