The following readings were obtained during differential levelling. Reduced Level (RL) of point A is 240,000 m. The fore sight and back sight between points A and TPI is 1.420 m and 2.024 m, respectively. Fore sight and back sight between points TPI and TP2 is 2.100 m and 1.986 m, respectively. The back sight from B is 1.722 m. These are marked on the given figure. What is the RL at turning point - 2 (TP2)? All values are in metres.

The following readings were obtained during differential levelling. Reduced Level (RL) of point A is 240,000 m. The fore sight and back sight between points A and TPI is 1.420 m and 2.024 m, respectively. Fore sight and back sight between points TPI and TP2 is 2.100 m and 1.986 m, respectively. The back sight from B is 1.722 m. These are marked on the given figure. What is the RL at turning point - 2 (TP2)? All values are in metres. Correct Answer 240.490 m

Concepts:

When staff is held vertically downward, then Height of instrument is

HI = Reduce Level (RL) + Staff Reading (SR)

Also, Reduce level of any other point on ground is calculated as:

RL = HI – BS/FS                          {BS is Back Sight and FS is Fore Sight}

Calculations:

RL of Point A = 240 m

HI at A = RL at A + BS at A

(HI)A = 240 + 2.024 = 242.024 m

(RL)TP1 = (HI)A  - FS at A = 242.024 – 1.42  = 240.604 m

HI when instrument is between TP1 and TP2,(HI)1-2 =  RL at TP1 + BS between TP1 and TP2

(HI)1-2 = 240.604 + 1.986 = 242.59 m

(RL)TP2 = (HI)1-2  - FS between TP1 and TP2 = 242.59 – 2.1 = 240.49 m

∴ The reduced level of TP2 is 240.49 m.

Related Questions

How far is point 'R' from Point 'T'? Statement (I): Point 'R' is 5 metres to the north of point 'M'. Point 'U' is 4 metres to the east of point 'R'. Point 'T' is to the west of point 'R' such that points 'U' 'R' and 'T' form a straight line of  metres. Statement (II): Point 'Z' is metres to the south of point 'T'. Point 'U' is  metres to the east of point 'T'. Point 'M' is  metres to the east of point 'Z'. Point 'R' is  metres to the north of point 'M'. Point 'R' lies on the line formed by joining points 'T' and 'U'.