Engineering Surveying

Surveying is the science and art of determining the relative positions of points on or near the earth’s surface and the angles and distances between them. It provides the geometric framework for mapping, engineering design, construction, and land division. Accurate surveys underpin the planning and execution of infrastructure projects, property boundaries, and scientific research.

Basis of Comparison	Plane Survey	Geodetic Survey
Definition	A surveying method that considers the earth's surface as a flat plane where all plumb lines are parallel	A surveying method that takes into account the true shape and size of the earth (geoid)
Earth's Curvature	Neglected - assumes earth is flat for calculations	Considered - accounts for earth's curvature in measurements
Area Covered	Small areas (less than 250 km²)	Large areas (more than 250 km²)
Accuracy	Less accurate for large areas	Highly accurate even for large areas
Measurement Techniques	Uses simple instruments like chain, tape, plane table, etc.	Uses sophisticated instruments like GPS, theodolites, total stations, etc.
Purpose	For local engineering projects, property boundaries, small-scale mapping	For national mapping, establishing control points, large infrastructure projects
Reference Surface	Assumes flat plane as reference	Uses ellipsoid or geoid as reference surface
Error Correction	Does not apply corrections for earth's curvature	Applies corrections for curvature, refraction, etc.
Plumb Lines	Considers all plumb lines as parallel	Accounts for convergence of plumb lines toward earth's center
Applications	Cadastral surveys, topographic surveys of small areas, construction surveys	National mapping, satellite positioning, large-scale engineering projects
Mathematical Treatment	Uses plane trigonometry	Uses spherical trigonometry
Control Points	Local control points with arbitrary coordinates	Global or national control points with precise geodetic coordinates

General Classification of Surveying

Surveying can be classified based on several criteria including purpose, instruments used, methods employed, and the nature of the field. Below is the comprehensive classification.

1. Based on the Nature of Field

Type	Description	Applications
Land Surveying	Deals with measurement of land and its boundaries	Property surveys, cadastral surveys, topographic surveys
Marine/Hydrographic Surveying	Measurement of bodies of water and coastal areas	Navigation charts, port construction, offshore drilling
Astronomical Surveying	Uses observations of celestial bodies	Determining absolute locations, azimuths, and time

2. Based on Purpose

Type	Description	Applications
Engineering Survey	Surveying for engineering projects	Roads, bridges, buildings, dams
Military Survey	Surveying for defense purposes	Strategic planning, missile guidance
Mine Survey	Surveying of underground and surface mines	Mineral exploration, mine planning
Geological Survey	Surveying for geological studies	Mineral exploration, earthquake studies
Archaeological Survey	Surveying of ancient sites	Preservation, documentation of historical sites

3. Based on Instruments Used

Type	Instruments	Characteristics
Chain Survey	Chain, tape, arrows, ranging rods	Simple, no angular measurements
Compass Survey	Prismatic compass, chain, tape	Angular measurements with compass
Plane Table Survey	Plane table, alidade, spirit level	Simultaneous observation and plotting
Theodolite Survey	Theodolite, chain/tape	Precise angular measurements
Leveling Survey	Dumpy level, staff	Elevation measurements only
Photogrammetric Survey	Aerial cameras, stereoplotters	Uses photographs for measurements
GPS Survey	GPS receivers	Satellite-based positioning

4. Based on Methods Employed

A. Triangulation

System of triangles measured to determine positions
Primary method for establishing horizontal control
Can be primary or secondary triangulation

B. Traversing

Series of connected lines with measured lengths and angles
Types: Closed traverse, Open traverse
Common in boundary surveys and route surveys

C. Leveling

Determination of elevations
Types: Differential leveling, Trigonometric leveling, Barometric leveling

D. Radiation

Measurements taken from a single central point
Used for small area surveys

E. Intersection

Locating points by intersecting lines from two known points
Used when direct measurement is difficult

5. Based on Accuracy Required

Type	Accuracy	Applications
First-order Survey	Highest accuracy (1:100,000 or better)	National control networks, geodetic surveys
Second-order Survey	High accuracy (1:50,000 to 1:100,000)	State or regional control surveys
Third-order Survey	Moderate accuracy (1:10,000 to 1:50,000)	Property surveys, engineering projects
Fourth-order Survey	Lower accuracy (less than 1:10,000)	Small local surveys, rough measurements

6. Special Survey Types

Type	Description
Cadastral Survey	Determination of land ownership boundaries
Topographic Survey	Mapping natural and man-made features with elevations
Route Survey	Surveying for linear projects like roads, pipelines
Construction Survey	Surveying for construction layout and control
Deformation Survey	Monitoring movement of structures or ground

Types of Surveying

Surveying methods are categorized by their purpose, techniques, and instruments. Below is a general list of common survey types:

Cadastral Survey: Defines property boundaries and land ownership.
Topographic Survey: Maps natural and man-made features at ground level.
Engineering Survey: Guides design and construction of roads, bridges, and buildings.
Control Survey: Establishes a network of reference points for other surveys.
Hydrographic Survey: Measures underwater features for navigation and engineering.
Mining Survey: Plans and monitors underground and surface mining operations.
Photogrammetric Survey: Derives measurements from aerial photographs or satellite images.
Geophysical Survey: Investigates subsurface conditions using physical methods (e.g., seismic).

Difference Between Plane and Geodetic Survey

Characteristic	Plane Survey	Geodetic Survey
Earth’s Curvature	Neglected—assumes a flat surface	Considered—requires spheroidal models
Area Coverage	Small areas (up to a few hundred km²)	Large areas (countries, continents)
Corrections Needed	Minimal or none	Corrections for curvature, refraction, gravity
Network Geometry	Traverses and local triangles	Large-scale triangulation, arcs of great circles
Applications	Site planning, cadastral work	National mapping, satellite positioning

Classification of Surveying

General Classification

General classification groups surveys by their end use and method:

By Purpose: cadastral, topographic, engineering, hydrographic
By Method: leveling, traversing, triangulation, photogrammetry
By Scale: large-scale (detailed), medium-scale (regional), small-scale (national)

Advanced Classification

Advanced methods leverage modern instruments and computational tools:

Global Navigation Satellite Systems (GNSS): Real-time kinematic and network solutions.
Terrestrial Laser Scanning (LiDAR): High-density point clouds for as-built modeling.
Unmanned Aerial Vehicles (UAV): Drone-based photogrammetry and LiDAR.
Robotic Total Stations: Automated angle and distance measurement with remote control.
Remote Sensing: Satellite imagery for large-area analysis and change detection.
Digital Leveling: Electronic read-outs and data logging for precision leveling.

Principles of Surveying

Fundamental principles ensure accuracy, reliability, and consistency in survey work:

Working from Whole to Part: Establish a robust control framework before detailed mapping.
Consistency: Use consistent methods and instruments throughout the project.
Accuracy and Precision: Balance the required precision with cost and time constraints.
Repetition: Repeat critical measurements to detect and reduce random errors.
Redundancy: Measure overlapping features to cross-check and validate results.
Closure: Ensure traverses and loops close within acceptable error limits.
Systematic Checks: Apply checks such as back-sights, opposite bearings, and level loops.
Documentation: Record all field notes, calibrations, instrument settings, and environmental conditions.
Adjustment and Compensation: Apply least-squares or balancing methods to distribute residual errors.
Proper Instrument Care: Calibrate, level, and maintain equipment to uphold measurement integrity.