单项选择题
（）is not a factor which will affect the accuracy of GPS receiver.
A.detective Availability B.local environmental conditions C.autonomous mode versus differential correction mode versus RTCM mode D.the averaging of recorded locations
单项选择题 （）is a digitized“picture”of a chart.
单项选择题 The heading of a vessel is indicated by what part of the compass? （）
单项选择题 The correction to be applied to a Loran-C reading when matching a sky wave to a ground wave may be found（）.
