By the end of this chapter, you will be able to:
Mastering these skills ensures you gather precise and reliable data, which is essential for successful surveying and construction projects in your trade.
A control survey demands a variety of specialized tools and materials, each vital for establishing accurate reference points and measurements. Surveyors in Kenya must be proficient in selecting and managing these resources to maintain precision and efficiency during fieldwork.
The hammer is an essential hand tool used primarily for driving markers such as iron pins into the ground, which serve as permanent control points in surveys.
There are several hammer types suited for control surveys, including claw hammers for general use-sledgehammers for driving larger pins, and mallets to avoid damaging delicate equipment. Each type is selected based on the terrain and the nature of the marker being installed.
A typical survey hammer weighs between 0.5 to 1.5 kilograms, with a steel head and a wooden or fiberglass handle for durability and shock absorption. Proper handling involves using controlled, accurate strikes to avoid bending or damaging survey markers.
Maintaining the hammer includes regular inspection for cracks in the handle and ensuring the head is securely attached. Safety during use requires wearing gloves and eye protection to prevent injuries from flying debris or accidental slips.
Pegs serve as temporary markers in control surveys, indicating station points or line intersections during measurement processes.
Survey pegs are typically made from hardwood or durable plastics, measuring about 30 to 50 centimeters in length. The pointed end facilitates easy insertion into the ground, while the top may be painted in bright colors for visibility.
Pegs are placed at control points to mark positions before permanent markers are installed. They assist in guiding measurements and help maintain alignment during surveying.
To prolong their usability, pegs should be stored in dry conditions to prevent rot and warping. Plastic pegs offer improved resistance to weather but can become brittle under prolonged UV exposure.
Spades are used in control surveys to excavate soil for installing permanent control markers or exposing existing ones.
A spade typically has a flat, rectangular steel blade with a straight edge, attached to a wooden or fiberglass handle approximately 90 centimeters long. This design allows efficient digging and soil removal.
Surveyors use spades to dig holes for iron pins or concrete bases that hold control points, especially in hard or compacted soils common in arid regions of Kenya.
Keeping the blade sharp and free from rust ensures effective digging. After use, spades should be cleaned and stored in a dry place to avoid corrosion and handle damage.
Unlike spades, shovels have a curved blade designed for scooping and moving loose soil or gravel, aiding in site preparation for control points.
Shovels have a broad, concave steel blade and a long handle to provide leverage. The blade is often slightly pointed to penetrate loose materials efficiently.
During surveys, shovels help clear debris or level the ground where control markers will be placed, ensuring stable and accurate installations.
Regular cleaning after use and checking for handle integrity prevent premature wear. Lubricating metal parts can protect against rust in humid environments like coastal Kenya.
Measuring tapes are fundamental for determining distances between control points with precision, especially in short-range surveys.
| Name | Specification | Use |
|---|---|---|
| Steel Measuring Tape | Length: 30m or 50m, Width: 13mm, Lockable reel | Measuring linear distances on-site, marking offsets |
Measuring tapes used in Kenyan land surveys must be durable, resistant to stretching, and easy to read under varying light conditions.
Surveyors select tapes based on length requirements and environmental conditions; steel tapes are preferred for accuracy and durability over cloth tapes, which can stretch and deform.
Proper tension is applied during measurement to avoid sagging, which can cause errors. The tape should be kept straight and aligned with the measurement line.
After use, tapes must be rewound carefully to prevent kinks. Regular calibration against known standards ensures continued measurement accuracy, crucial for cadastral surveys.
Ranging rods are vertical markers used to establish straight survey lines and signal points from a distance.
| Name | Specification | Use |
|---|---|---|
| Ranging Rod | Length: 2m to 3m, painted in alternating red and white bands | Marking alignment and sighting lines |
These rods enhance visibility in open fields and assist in maintaining line-of-sight during control point determination.
Typically made from lightweight wood or fiberglass, ranging rods are painted in bright contrasting colors for clear visibility even in dense vegetation.
Surveyors place ranging rods at intervals along survey lines to guide measurements and instrument setups, especially when using theodolites or total stations.
Rods should be handled gently to avoid breakage and stored in protective cases. Repainting may be necessary to maintain their visibility over time.
The total station is an advanced electronic instrument combining the functions of a theodolite and electronic distance measurement (EDM), essential for precise control surveying.
| Name | Specification | Use |
|---|---|---|
| Total Station | Angular accuracy: 1 to 5 arc seconds; EDM range: up to 3,000m; Data storage: internal memory or external card | Measuring horizontal and vertical angles, distances, and recording data digitally |
Kenyan surveyors rely on total stations for rapid and accurate data collection, particularly in urban and complex terrains.
The instrument integrates a telescope for angle measurement, an EDM for distance calculation, and onboard software for data processing and storage.
Operators set up the total station over a known point, level the instrument, and sight targets such as prisms on ranging rods to capture spatial data.
Regular calibration by authorized service centers ensures measurement accuracy. Field care includes protecting the instrument from dust, moisture, and mechanical shock.
Global Navigation Satellite System (GNSS) receivers provide geospatial positioning by triangulating signals from satellites, enhancing control survey efficiency.
| Name | Specification | Use |
|---|---|---|
| GNSS Receiver | Multi-constellation support (GPS, GLONASS, Galileo); Accuracy: sub-meter to centimetre level with corrections | Determining precise coordinates for control points |
GNSS technology has revolutionized surveying in Kenya, especially for large-scale and remote area surveys.
GNSS receivers process satellite signals to calculate the receiver’s position in latitude, longitude, and elevation, corrected by differential techniques for enhanced precision.
They enable rapid establishment of control networks without the need for intervisible points, suitable for rugged or obstructed environments.
Receivers require regular firmware updates and battery charging to maintain functionality. Protecting antennas from physical damage and moisture is critical in field conditions.
The theodolite is an optical instrument used to measure horizontal and vertical angles, fundamental to traditional control surveying.
| Name | Specification | Use |
|---|---|---|
| Theodolite | Angular accuracy: typically 5 to 20 arc seconds; Telescope magnification: 20x | Measuring precise angles between survey points |
Though increasingly supplemented by total stations, theodolites remain vital in many Kenyan survey operations for their reliability.
The instrument includes a rotating telescope mounted on a base with graduated circles for angle reading, and leveling screws for precise alignment.
Surveyors carefully level the theodolite, sight targets, and record angular measurements manually, requiring skilled operation for accuracy.
Protecting the theodolite from shocks and moisture extends its lifespan. Regular checks against known angular standards maintain measurement precision.
Sand is used in control surveys mainly as a bedding material for setting control point markers to ensure stability and prevent shifting.
Clean, coarse sand provides good drainage and compaction, reducing movement of embedded markers in various soil types found in Kenya.
Surveyors place a layer of sand at the base of holes dug for iron pins or concrete monuments to cushion and stabilize the markers.
Sand should be free from organic matter and debris to maintain integrity. Sourcing from approved quarries or riverbeds ensures consistency in material quality.
Cement is used to secure permanent survey markers by creating concrete bases that resist environmental forces and human interference.
Ordinary Portland Cement (OPC) conforming to Kenya Bureau of Standards (KEBS) specifications is preferred for durability and strength in marker foundations.
Proper mixing ratios of cement, sand, and aggregate are critical to achieve a solid base. Surveyors mix and pour concrete around iron pins or monuments in prepared holes.
After placement, concrete requires curing for at least seven days to reach optimal strength. Protecting curing markers from rain and disturbance ensures longevity.
Iron pins are permanent markers driven into the ground to denote control points, serving as reference locations for surveys.
| Name | Specification | Use |
|---|---|---|
| Iron Pins | Steel rods, typically 16mm diameter, 450mm length, pointed tip | Marking fixed control points in the field |
These pins are fundamental in establishing the physical framework for cadastral and engineering surveys.
Iron pins are made from corrosion-resistant steel to withstand soil moisture and environmental exposure over many years.
Pins are driven into pre-dug holes, often surrounded by concrete for stability. The top of the pin is left slightly above ground level for easy identification.
Periodic inspection ensures pins remain visible and undisturbed. Surveyors verify their positions during subsequent surveys to maintain network accuracy.
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Create a free accountThis chapter covered the essential tools, equipment, and materials required for control surveys, including items such as hammers, pegs, spades, shovels, measuring tapes, ranging rods, total stations, GNSS receivers, theodolites, sand, cement, and iron pins. It explained the specific role each plays in facilitating accurate and efficient survey data collection. The chapter then explored various methods of control survey data collection, focusing on traverse techniques, the use of GNSS technology, and traditional taping methods. Following this, it detailed the practical process of collecting control survey data, emphasizing the importance of precision and proper handling of instruments. Finally, the chapter discussed the computation of control survey data, outlining how raw measurements are processed to produce reliable survey results that inform subsequent project stages. Together, these topics provide a comprehensive understanding of the procedures and tools fundamental to successful control surveying.
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