Set out construction works involve transferring design information from plans and drawings onto the ground to guide the construction process. In land surveying, accuracy and precision in this task are critical as errors can lead to costly rework or structural failure. Surveyors use specialized tools and equipment to achieve reliable set out, adapting to diverse environments from urban building sites to rural infrastructure projects in Kenya.

4.1 Tools, equipment and materials

A comprehensive understanding of the tools, equipment, and materials used in setting out construction works is fundamental for land survey professionals. Each instrument serves a specific purpose in ensuring precise measurements, alignment, and positioning of structures on site. The choice of equipment depends on the project scale, site conditions, and accuracy requirements.

4.1.1 Total station

The total station is a versatile electronic/optical instrument that integrates the functions of a theodolite and an electronic distance measurement (EDM) device. It enables surveyors to measure angles and distances simultaneously, facilitating rapid and accurate data collection essential for construction set out.

Specifications and capabilities of total stations

• Measures horizontal and vertical angles to determine exact directions for setting out building corners and alignments.
• Uses EDM to calculate distances to reflectors or prisms with millimeter precision.
• Stores measurement data digitally, reducing transcription errors and enabling immediate data processing.
• Can interface with computers and field controllers for automated coordinate computations.
• Requires regular calibration to maintain angular and distance accuracy.

Application in construction set out

The total station is used to establish control points, set out building lines, and stake out infrastructure alignments. For instance, at a county government office construction site, surveyors use the total station to mark foundation corners by inputting design coordinates and projecting them onto the ground. This reduces manual measurement errors and speeds up the set out process.

Maintenance and handling

Proper care extends the lifespan and accuracy of total stations:

• Keep lenses clean and free from dust using a soft brush or lens tissue.
• Avoid exposure to extreme temperatures and moisture to prevent electronic damage.
• Calibrate angular and distance measurements periodically according to manufacturer guidelines.
• Transport in padded cases to protect against shocks and vibrations.
• Ensure batteries are charged before field deployment and store spares.

4.1.2 Reflector prism

The reflector prism is an optical device used in conjunction with the total station to reflect the EDM signal back to the instrument, enabling accurate distance measurement.

Types and specifications of reflector prisms

• Single prisms are most common for general construction set out.
• Mini prisms facilitate measurements in locations with limited access.
• Prism poles allow the prism height to be adjusted to instrument height or design requirements.
• Prism constant must be accounted for in measurements to correct distance readings.
• Proper mounting ensures prism stability, minimizing errors from movement.

Operational use on site

Surveyors position the prism on marked points or moving targets to measure distances from the total station. At a hospital expansion project, the prism is mounted on a pole and moved to foundation points to verify their coordinates against design values, ensuring compliance with architectural plans.

Care and upkeep

• Clean prism surfaces with lens cleaning solution to maintain reflectivity.
• Store in protective cases to avoid scratches or breakage.
• Check the prism constant regularly and apply corrections during data processing.
• Inspect mounting accessories for wear and replace as needed.
• Avoid direct sunlight on prism surfaces during measurements to reduce signal distortion.

4.1.3 Level with Oral

The level with oral is an optical instrument used for determining height differences and establishing horizontal planes during construction set out.

Types and features of levels with oral

• Automatic levels compensate for slight tilts automatically, improving accuracy.
• Digital levels offer direct reading of height differences, reducing manual calculations.
• Optical levels require manual focusing and sighting but remain widely used for accuracy.
• Tripods must be sturdy and leveled to avoid errors.
• Bubble vials assist in quick approximate leveling before fine adjustments.

Application in construction set out

Levels with oral are essential for establishing reference elevations for foundations, slabs, and other horizontal elements. For example, at a retail mall construction site, the surveyor uses an automatic level to transfer bench marks and set design heights for floor slabs, ensuring uniformity and compliance with structural requirements.

Handling and maintenance

• Keep lenses clean and free from fog or dirt.
• Avoid knocking or dropping the instrument to prevent internal damage.
• Store in protective cases when not in use.
• Check and adjust bubble levels regularly.
• Calibrate the instrument periodically to ensure accuracy.

4.1.4 Levelling staff

The levelling staff is a graduated rod used alongside the level to measure vertical distances between points.

Types and specifications of levelling staffs

• Aluminium staffs are lightweight and resistant to weather.
• Wooden staffs are economical but require maintenance to prevent warping.
• Telescopic staffs enhance portability and adaptability.
• Invar staffs provide accuracy in scientific or precise engineering surveys.
• Graduations must be clear and legible for accurate readings.

Usage in the field

Surveyors hold the levelling staff vertically on points being measured, while the level operator reads the staff through the instrument’s telescope. At a cooperative farm irrigation project, levelling staffs are used to check field gradients to ensure proper water flow, critical for crop irrigation efficiency.

Care and storage

• Store staffs in dry conditions to prevent corrosion or decay.
• Clean graduations regularly for clear visibility.
• Handle carefully to avoid bending or damage.
• Inspect for accuracy periodically, especially after rough handling.
• Use protective covers during transport.

4.1.5 Pegs

Pegs are physical markers driven into the ground to indicate set out points such as corners, alignments, or levels.

Types and materials of pegs

• Wooden pegs are economical and widely used but prone to decay.
• Bamboo pegs are light and eco-friendly but less durable.
• Plastic pegs resist weathering and can be reused.
• Metal pegs provide durability but may require specialized tools for insertion.
• Painting pegs improves visibility in dense vegetation or low light.

Role in construction set out

Surveyors use pegs to mark exact positions of structures such as building corners, road edges, or utility lines. At a county government road improvement project, pegs delineate road shoulders, ensuring contractors adhere to design specifications precisely.

Installation and maintenance

• Drive pegs firmly into the ground to prevent displacement.
• Use a hammer or mallet for controlled insertion.
• Mark pegs with identification numbers or codes for reference.
• Replace damaged or missing pegs promptly to maintain site accuracy.
• Remove pegs after construction completion or when no longer needed.

4.1.6 Hammer/mallet

Hammers and mallets are hand tools used to drive pegs into the ground or make fine adjustments during set out.

Types and specifications

• Claw hammers are common for general pegging and minor demolition.
• Wooden mallets prevent splitting or damage to wooden pegs.
• Rubber mallets protect delicate surfaces when adjusting instruments.
• Ball peen hammers are specialized for metalwork but occasionally used on site.
• Sledgehammers are suitable for heavy stakes in hard ground.

Practical use in set out works

Surveyors use hammers or mallets to install pegs securely without causing damage that may affect measurements. For example, at a university expansion site, wooden mallets are preferred to avoid splitting pegs that mark building lines.

Care and storage

• Keep hammer and mallet handles dry and free from cracks.
• Store tools in toolboxes or racks to avoid damage.
• Inspect heads for looseness or wear and replace if necessary.
• Clean tools after use to prevent rusting.
• Use appropriate tool type for the task to prolong lifespan.

4.1.7 GNSS receiver

The Global Navigation Satellite System (GNSS) receiver is an advanced electronic device used to determine geographic coordinates with high accuracy using satellite signals.

Features and specifications

• Supports multiple satellite constellations for improved accuracy and reliability.
• Real-Time Kinematic (RTK) correction enhances positional accuracy to centimeter level.
• Stores large volumes of data for post-processing or immediate use.
• Communication features enable integration with field controllers.
• Battery capacity supports full day’s surveying activity.

Application in construction set out

GNSS receivers are increasingly used for rapid and accurate location of set out points, especially in open areas. At a county water project, surveyors use GNSS to set out pipeline alignments over long distances where traditional line-of-sight instruments are impractical.

Handling and maintenance

• Protect antenna and receiver from impacts and moisture.
• Regularly update firmware and software to maintain functionality.
• Calibrate equipment according to manufacturer instructions.
• Ensure batteries are fully charged before field deployment.
• Store in padded cases to prevent damage during transport.

4.1.8 Measuring tape

Measuring tapes are simple but essential tools for direct measurement of distances during set out works.

Types and specifications

• Steel tapes provide durability and resistance to stretching.
• Fibreglass tapes are lightweight and resistant to moisture.
• Cloth tapes are less durable but useful for quick measurements.
• Metric graduations are standard for accurate metric system measurements.
• Reel tapes allow easy handling on large sites.

Use in setting out

Measuring tapes are used for short distances, verification of set out points, and checking offsets from control lines. For example, at a retail store construction site, tapes are used to confirm distances between pegged points and ensure compliance with architectural drawings.

Care and storage

• Retract tapes slowly to avoid kinks or damage.
• Keep tapes clean and dry to prevent rust or deterioration.
• Store tapes in protective cases or holders.
• Avoid bending or twisting tapes excessively.
• Regularly check tape graduations for wear or fading.

Chapter Summary

This chapter provided a comprehensive overview of the tools, equipment, and materials essential for setting out construction works, including instruments such as the total station, reflector prism, level with oral, levelling staff, pegs, hammer or mallet, GNSS receiver, and measuring tape. Emphasis was placed on the importance of conducting a thorough site safety assessment before commencing any setting out activities to ensure a secure working environment. The identification of existing control points was discussed as a critical step in establishing accurate references for construction. The chapter explored the meaning of setting out as the process of transferring design information onto the ground, followed by a detailed examination of its purpose and importance in guiding construction accuracy and quality. Various methods of setting out were analyzed, including by coordinates, using theodolite and level, and by offset techniques. Practical applications of setting out vertical and horizontal curves were covered to ensure alignment with design specifications. Finally, the chapter addressed the specific procedures for setting out buildings and structures, trenches, and slope stakes, highlighting the precision required for successful construction outcomes.