Question

STA Hil ROD ELEV ADJD REMARKS 100.00 BENCHMARK 100 EL 100.00 105.62 TP1 98.75 104.37 97.46 TP2 98.35 87.73 TP3 93.68 92.79 TP4 98.40 96.90 TPS 103.10 97.49 TP6 102.90 99.94 BENCHMARK 100 EL100.00

Answer 1

For BM:

BS = HI at BM - Elevation at BM

= 105.62 - 100

= 5.62

For TP1:

FS = HI at BM - Elevation at TP1

= 105.62 - 98.75

= 6.87

BS = HI at TP1 - Elevation at TP1

= 104.37 - 98.75

= 5.62

For TP2:

FS = HI at TP1 - Elevation at TP2

= 104.37 - 97.46

= 6.91

BS = HI at TP2 - Elevation at TP2

= 98.35 - 97.46

= 0.89

Similarly for other stations FS and BS can be obtained as shown in the following table:

Station	BS	HI	Rod (FS)	Elevation
BM	5.62			100
		105.62
TP1	5.62		6.87	98.75
		104.37
TP2	0.89		6.91	97.46
		98.35
TP3	5.95		10.62	87.73
		93.68
TP4	5.61		0.89	92.79
		98.4
TP5	6.2		1.5	96.9
		103.1
TP6	5.41		5.61	97.49
		102.9
BM			2.96	99.94

Error (e) = Elevation of BM obtained - Elevation of BM given

= 99.94 - 100

= - 0.06

As the error is negative correction should be positive.

Therefore total correction = + 0.06

Average correction = Total correction / Number of stations

= 0.06 / 7

Adjustment and adjusted elevation for each station is shown in the table below:

Station	BS	HI	Rod (FS)	Elevation	Adjustment	Adjusted elevation
BM	5.62			100	-	100
		105.62
TP1	5.62		6.87	98.75	(+ 0.06/7) * 1 = 0.00857	98.75857
		104.37
TP2	0.89		6.91	97.46	(+ 0.06/7) * 2 = 0.017143	97.477143
		98.35
TP3	5.95		10.62	87.73	0.025714286	87.75571429
		93.68
TP4	5.61		0.89	92.79	0.034285714	92.82428571
		98.4
TP5	6.2		1.5	96.9	0.042857143	96.94285714
		103.1
TP6	5.41		5.61	97.49	0.051428571	97.54142857
		102.9
BM			2.96	99.94	0.06	100