# Civil Engineering - Surveying - Discussion

Discussion Forum : Surveying - Section 1 (Q.No. 49)
49.
Keeping the instrument height as 1.5 m, length of staff 4 m, the slope of the ground as 1 in 10, the sight on the down-slope, must be less than
30 m
25 m
20 m
15 m
Explanation:
No answer description is available. Let's discuss.
Discussion:
26 comments Page 1 of 3.

Roohullah jan said:   4 years ago
In a simple way we can say that;

Let consider the slope is downward which 1 in 10.

So at 10m, the staff reading becomes 1. 5+1=2. 5m (staff reading).

At 20 m distance reading becomes 3. 5m.

Similarly, at 25 m distance, the reading becomes 4m. Which is the full length of the staff?

Thanks.
(9)

Awais khan said:   3 years ago
By similar triangles;
1/10 = (4-1.5)/X
X = 2.5(10) = 25m.
(6)

Sameer sopori said:   6 years ago
If we are levelling on the sloped surface then we need to keep staff near the instrument, otherwise, it will not be visible inside the instrument because of the slope (if the distance is more).
so here is the formula, UNDER WHICH DISTANCE WE MUST KEEP STAFF,
Sight= (Staff ht.- instrument ht.)/(1/10)
= (4 - 1.5) /0.1,
= 2.5/0.1,
= 25m.

If you will keep the staff more than 25m away from the instrument , IT WILL NOT BE VISIBLE INSIDE THE INSTRUMENT,
(5)

Soumya said:   3 years ago
If downslope 25m, If Upward slope asked then it's 55m.
(2)

Ziaullah said:   4 years ago
4 - 1.5 = 2.5.
2.5 * 10 = 25.
(1)

Mamatamayee said:   6 years ago
Thanks @Sameer.

Naveed Kamal Marwat said:   4 years ago
Downward 25m.

Upward 45m.

Zomuana said:   4 years ago
Thanks a lot @Sameer.

Waleed said:   4 years ago
Very helpful, Thank you @Sameer.

Vikash said:   4 years ago
Thanks all.