The use of the spirit level fixed to the telescope of a leveling instrument is
ATo make the line of sight vertical
BTo make the line of sight horizontal
CTo compute the difference in elevations
DTo establish the G.T.S. Bench mark
ATo make the line of sight vertical
BTo make the line of sight horizontal
CTo compute the difference in elevations
DTo establish the G.T.S. Bench mark
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