Surveying (Civil)

Surveying types:

• Plane survey: small area, earth treated as flat.
• Geodetic survey: large area, curvature considered.

Instruments:

• Chain (20 m, 30 m), tape (metallic, invar).
• Compass: measures bearings.
• Theodolite: horizontal + vertical angles.
• Total station: digital theodolite + EDM.
• Levelling instrument: dumpy level, auto level.
• GPS / GNSS: satellite-based.
• Drones: modern surveying.

Chain Surveying:

• Direct measurement of distances.
• Suitable for small flat areas.
• Methods: cross-staff, optical square.

Compass Surveying:

• Magnetic bearings (whole circle or quadrantal).
• Local attraction, dip, declination.

Theodolite Surveying:

• Horizontal angles by repetition / reiteration.
• Vertical angles for height/depth.

Levelling:

• Determining heights (elevations).
• Reduced level (RL).
• Height of Instrument (HI) method.
• Rise and Fall method (more accurate).
• Benchmarks (BM): permanent reference points.

Errors:

• Cumulative: systematic, increase with measurements.
• Compensating: random, tend to cancel.
• Mistakes: gross errors, must be removed.

Topographic Survey: shows natural & artificial features with contours.

Contour Interval (CI): vertical distance between two contours.

• Steep slope: contours close together.
• Flat ground: contours spread out.

RRB JE focus: chain length, theodolite uses, levelling methods, RL calculations.