the instrument is to be shifted frequently

fly levelling is being done over long distance

many readings are to be taken from a single setting of the instrument

all of the above

equidistant from A and B

closer to the higher station

closer to the lower station

as far as possible from the line AB

inversely proportional to the scale of the map

directly proportional to the flatness of ground

larger for accurate works

larger if the time available is more

contour line

horizontal equivalent

contour interval

contour gradient

2 m

5 m

10 m

20 m