Surveying Short Notes for Civil Engineering Exams

1. Fundamentals of Surveying

• Primary Objective: Map taiyaar karna aur relative positions find karna.

• Main Principles: 1. Whole to Part: Errors ko accumulate (ikattha) hone se rokne ke liye.

  2. Location of a Point: Kam se kam do measurements (linear ya angular) se point fix karna.

• Classification:

  • Plane Surveying: Earth ka curvature neglect kiya jata hai ($< 195.5 \text{ km}^2$ area ke liye).

  • Geodetic Surveying: Earth ka curvature consider kiya jata hai (Large areas ke liye).

2. Linear Measurements (Chain & Tape)

• Standard Chain Lengths: 20m (100 links) aur 30m (150 links).

• Important Corrections:

  • Temperature Correction: $C_t = \alpha (T_m - T_o) L$

  • Pull Correction: $C_p = \frac{(P_m - P_o)L}{AE}$

  • Sag Correction: Hamesha Negative hota hai. $C_s = \frac{W^2 L}{24 P^2}$

  • Slope Correction: $C_{sl} = \frac{h^2}{2L}$ (Hamesha Negative).

3. Compass Surveying

• Prismatic Compass: Broad needle, Whole Circle Bearing (WCB) $0^\circ \text{ to } 360^\circ$ read karta hai.

• Surveyor’s Compass: Edge bar needle, Quadrantal Bearing (QB) $0^\circ \text{ to } 90^\circ$ read karta hai.

• Magnetic Declination: True North aur Magnetic North ke beech ka angle.

  • $\text{True Bearing} = \text{Magnetic Bearing} \pm \text{Declination}$ (+ for East, - for West).

• Local Attraction: Agar $(\text{FB} - \text{BB}) \neq 180^\circ$, toh station local attraction se affected hai.

4. Levelling

• Important Terms: * Back Sight (BS): Instrument set karne ke baad li gayi pehli reading.

  • Fore Sight (FS): Last reading shift karne se pehle.

  • Bench Mark (BM): Fixed reference point jiska RL (Reduced Level) pata ho.

• Methods:

  1. HI Method: Fast hai, lekin intermediate points par check nahi lagata.

  2. Rise & Fall Method: Zyada accurate hai, har point par check lagata hai.

• Combined Correction (Curvature + Refraction): $C = -0.0673 D^2$ (meter mein, jahan $D$ km mein hai).

5. Contouring

• Contour Interval: Do consecutive contour lines ke beech ka vertical distance.

• Characteristics:

  • Steep Slope: Lines paas-paas hoti hain.

  • Uniform Slope: Lines ke beech equal distance hota hai.

  • Ridge/Valley Lines: Lines $90^\circ$ par cross karti hain.

  • Overhanging Cliff: Sirf yahan lines ek dusre ko cross kar sakti hain.

6. Theodolite & Traverse

• Temporary Adjustments: Centering, Levelling, aur Elimination of Parallax.

• Latitudes (L): North-South component ($L = l \cos \theta$).

• Departures (D): East-West component ($D = l \sin \theta$).

• Closing Error: Agar $\sum L \neq 0$ aur $\sum D \neq 0$. Isse Bowditch's Rule se correct kiya jata hai.

7. Tacheometry

• Distance Formula: $D = ks + c$

  • $k = f/i$ (Multiplicative Constant, usually 100).

  • $c = f+d$ (Additive Constant, Anallatic lens ke liye 0 hota hai).