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[单选题]
观测竖直角时,盘左读数为90°23′24″,盘右读数为269°36′12″,则指标差为()
A.24″
B.-12″
C. -24″
D. 12″
查看答案
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A.24″
B.-12″
C. -24″
D. 12″
A . 2º15′40″
B . 2º45′10″
C . 2º45′20″
D . 2º45′00″
用DJ6型光学经纬仪观测某一目标,盘左竖直度盘读数为71°45'24",该仪器竖盘(盘左)注记如表所示,测得竖盘指标差x=+24",试求该目标正确的竖直角α为多少?