Introduction to Surveying

1. Introduction to Surveying

Surveying is the technique and science of accurately measuring and determining the three dimensional positions of points and the distances and angles between them'

These measurements are then used to produce maps, layouts for construction and development.

Surveying also refers to the process of measuring and mapping the environment using mathematical, engineering, and scientific methods.

It helps determine land boundaries, plan construction projects and create maps.

Surveying is a vital in fields like civil engineering, architecture and real estate.

It involves tools such as levels, theodolites and GPS to collect accurate data on distances, angles and elevations.

1.1. Defination and Importance

Definition:

Surveying refers to the process of measuring distances, angles and positions on the earth's surface to determine land boundaries , locations and features.

Importance of Surveying

1.Land measurements and Boundary Identification- Establishes accurate property lines to avoid disputes.

2.Construction Planning- Provides precise data needed for building roads , bridges and structures.

3.Map Preparation- Helps create topographic and cadastral maps for planning and development.

4.Infrastructure development- Essential for layout and alignment in civil engineering projects.

5.Legal Documentation- Used in land registration, ownership transfer and legal record.

6.Resource Management- Aids in managing natural resources like water, minerals and forests.

7.Urban Planning- Supports zoning road layout, drainage systems and city expansion. 

2. Surveying Instruments and Tools

Surveying Instruments are tools used to measure distances, angles and elevations on land.

They include: measuring tape, theodolite total station

Each tool serves as a specific purpose depending on the type and accuracy of the survey being conducted.

2.1. Traditional Instruments

1.Chain and Tape- Used for measuring distances (examples Gunter's chain, steel tape)

2. Compass-Used for measuring bearings and directions of survey lines.

3. Dumpy Level- Used in levelling to determine height differences.

4.Theodolite-Measures horizontal and vertical angles precisely.

5. Plane Table- Combines field observation and map-making on the spot.

6. Ranging Rod- Used to mark position in the field and for aligning survey lines.

7. Plumb Bob- Used for vertical referencing and transferring points.

8. Levelling Staff- Graduated rod used with levelling instrument to measure vertical distances.

These tools were the foundations of early surveying before modern electronic equipments like total stations and GPS were introduced.

2.2. Modern Instruments

1.Total Station -Combines electronic theodolite and EDM for measuring angles and distances accurately.

2. Global Positioning System (GPS) -Uses satellite signals to determine precise locations and coordinates.

3. Digital Level -Electronic levelling device for fast and accurate height measurements.

4.Dumpy Level (Modern Version) -  Still used but enhanced with digital features.

5. Lasers Scanner-Captures 3D data of surfaces and environments quickly.

6. Drone (UAV) -Captures aerial imagery and data for mapping and topographic surveys.

7. GIS (Geographic Information System) -Used for analyzing spatial data and creating maps.

8. Robotic Total Station -Operated remotely tracks and measures without needing multiple operations.

These instruments increases efficiency, accuracy and speed in modern surveying.

3. Methods and Techniques

Surveying methods are techniques used to determine the positions, distances and elevations of points on the earth's surface.

Common methods include: 

1.Triangulation -Based on measuring angles in triangles.

2. Traversing -Involves measuring distances and angles in a connected line path.

3. Levelling -Determines height differences between points.

4. Tachymetry- Quick method using a theodolite for measuring distance and elevations.

5. GPS Surveying - Uses satellites for accurate positioning.

6. Photogrammetry - Uses photos (aerial or ground) for mapping.

These techniques helps in producing maps, setting boundaries and planning construction works.

3.1. Chain surveying

Chain surveying is the simplest type of land surveying. It involves measuring distances using chain or tape and is mainly used for small, level areas. It relies on linear measurements only, with no angle measurements involved.

Key Features

. Suitable for open and flat areas. 

. Requires simple tools like chain, tapes, arrows and ranging rods.

. Ideal for plots with few details and clear boundaries.

Limitations

. Not suitable for large or hilly areas.

. Accuracy can be affected by obstacles or uneven ground.

. Obstructions- Trees, building, or uneven ground can block chaining and sighting.

. Less accurate as compared to modern methods like total stations or GPS.

. Time consuming especially when many offsets or details are needed.

. Not ideal for detailed work- limited in showing elevation or complex features.

. Weather-dependent -Rain or wind can affect tape measurements and visibility.

3.2. Levelling and contouring

Levelling is the process of determining the height of points above or below a fixed reference point (benchmark).

Common instruments used include the dumpy level and levelling staff. 

Types of levelling include differential levelling and fly levelling.

It's used to create level surface, design roads or check slopes.

Contouring involves connecting points of equal elevation to form contour lines on map. These lines show the shape and height of landforms like hills and valleys.

Contour lines close together indicate steep slopes while widely spaced lines shows gentle slopes. 

Contour helps in planning drainage, roads and irrigation systems.

Purpose:

These methods are essential for planning, designing and constructing infrastructure accurately and safely.