1. Types of Surveys 📐

Survey Type	Purpose	Precision Required
Cadastral	Property boundaries, land titles	High (legal purposes)
Topographic	Elevation, terrain features	Medium-High
Construction	Setting out buildings, roads	Very High (mm level)
Hydrographic	Water body depths, shorelines	High (navigation safety)
Geodetic	Large area control networks	Highest (sub-mm)

2. Leveling 📊

Determining elevation differences between points.

Basic Leveling Equation

Elevation B = Elevation A + BS - FS

HI = Elevation A + BS

BS (Backsight)

Reading on known elevation point. Always ADDED to elevation.

FS (Foresight)

Reading on unknown point. Always SUBTRACTED from HI.

HI (Height of Instrument)

Elevation of line of sight = Known Elev + BS

Leveling Errors

Curvature: c = 0.0785D² (meters, D in km)
Refraction: r = 0.011D² (meters, D in km)
Combined (c-r): 0.0675D² ≈ 0.07D²
At 1 km: c-r ≈ 0.07m = 7cm error!

3. Traverse Surveying 🔄

Angular Closure

Interior angles sum = (n-2) × 180°

Exterior angles sum = (n+2) × 180°

Error distribution: Equally distribute angular error to all angles

Linear Closure

Departure = Distance × sin(Bearing)

Latitude = Distance × cos(Bearing)

ΣDep = 0 and ΣLat = 0 for closed traverse

Precision = Linear error / Total distance (e.g., 1:5000)

Adjustment Methods

Compass Rule: Correction ∝ Distance (for equal angular & linear precision)
Transit Rule: Correction ∝ Lat/Dep (for higher angular precision)
Least Squares: Most rigorous, minimizes sum of squares

4. Area Computation 📏

Double Meridian Distance (DMD)

Area = ½ Σ(DMD × Lat)

First DMD = First Departure
Next DMD = Prev DMD + Prev Dep + Curr Dep
Last DMD = Last Departure (check!)

Coordinate Method

2A = Σ(Xn(Yn+1 - Yn-1))

Or: 2A = Σ(Yn(Xn-1 - Xn+1))

Faster for coordinate-based surveys

5. Surveying Instruments 🔭

Total Station

Electronic theodolite + EDM combined. Measures angles and distances simultaneously.

Accuracy: 1-5mm + 1-3ppm for distance; 1" for angles

GNSS Receiver

Satellite-based positioning. RTK mode: cm-level accuracy in real-time.

Static survey: mm accuracy with post-processing

Level

Automatic/digital level for height determination. Self-leveling compensator.

Precision levels: ±0.3mm per km double-run

6. Practice Questions 📚

Common Board Exam Questions

Q1: In a 5-sided closed traverse, what should be the sum of interior angles?

A: (n-2) × 180° = (5-2) × 180° = 3 × 180° = 540°

Q2: The BS reading is 2.543m and FS is 1.876m. If BM elevation is 100.000m, what is the elevation of the new point?

A: HI = 100.000 + 2.543 = 102.543m. New Elev = 102.543 - 1.876 = 100.667m

Q3: What is the combined curvature and refraction error at 2km?

A: c-r = 0.0675 × D² = 0.0675 × 4 = 0.27m

🔥 GE Challenge 🔥

Master field surveying! Leveling, traversing, area computation, instruments - precise measurements in any terrain!

Measure twice, mark once - the surveyor's creed!

Surveying