Civil Engineering - Surveying - Discussion

Solution;

Note: Here in Q it is not 1 1/2 actually it is only 1/2 so,
if upward slope asked then i.e +ve.
Sight= (Staff ht + instrument ht.)/(Slope)
Sight=(4+1/2)(1/10)
Sight=(4.5)*(10)
Sight=45 m.

And It will be 55 m in case if 1 1/2 only.

TanQ= (4-1.5)/x = 1/10 = 2.5/x.
= 25m.

25 m is the correct answer.

Calculations:

Given,
Height of instrument (HI) = 1.5 m.
Length of staff = 4 m.
Ground slope (downslope) = 1/10.
x = 25 m.

@All , Here is the explanation.


If we keep the instrument at downside on slope surface (1/10), then staff distance should not be more than 15m, otherwise, we can not see the reading on staff, as per this equation.

The Horizontal distance = height of staff/ slope ratio, d= 1.5/(1/10) = 15m.

Then the instrument will be moved to forward (upward direction) for BACK SIGHT reading, then we need to keep the instrument at this distance = (4-1.5) / (1/10) = 25m, more than 25m we can not see the staff or staff readings.

So, the total horizontal distance is 15+25 = 45m.

I also agree with 15 m.

Yes, 15m is the right answer. I agree with it.

I think height should be 15 m because here is up gradient, not down gradient so here 1.5 m height should be read by instrument, so

L =height/slope =1.5/(1/10)=15m.

15m will be the right answer.

h = height of the instrument+height of staff/gradient.

Slope = h^2/(2x staff length).

h = 3/2+4/10 = 1.5 + 0.4 = 1.9.

Slope = 1.9^2/(2*4) = 0.45 m.

For 100 m slope = 45 m.