A levelling work was carried out along a falling gradient using a dumpy level and a levelling staff of 3 m height. The following successive readings were taken 1.55, 2.655, 0.54, 1.68 m. The level was shifted after the second reading.
What is the correct order of booking the readings in the field book?
(BS: back sight, FS: Fore sight, IS: Intermediate sight)
1
BS, IS, FS, BS
2
BS, IS, IS, FS
3
BS, FS, BS, FS
4
BS, FS, IS, FS