Establishing cadastral survey control points is a fundamental step in land surveying that ensures accurate boundary delineation and legal land parcel identification in Kenya. These control points form the spatial framework upon which cadastral surveys are based, facilitating precise measurements and reducing disputes. For land survey professionals, mastery of the tools, equipment, and methodologies used in establishing these control points is vital to uphold the integrity of land records and support land administration systems.

2.1 Tools, equipment and materials for establishment of cadastral control points

In cadastral surveying, selecting appropriate tools and equipment is critical to achieving high accuracy and reliability. Surveyors in Kenya utilize a blend of traditional and modern technologies, such as traversing instruments and Global Navigation Satellite Systems (GNSS), depending on the terrain, survey scale, and project requirements. Understanding the specifications, applications, and maintenance of these tools ensures consistency in establishing control points under diverse field conditions.

Angle and distance measuring equipment

These instruments measure the horizontal angles, vertical angles and distances from which the coordinates of new control points are computed. Their accuracy sets the accuracy of the whole control network, so they must be calibrated and in good adjustment before fieldwork. Example: before establishing control for a subdivision for a teachers' SACCO, a survey firm checks its total station's EDM on a calibration baseline.

• Total station: The main instrument for traversing and trilateration; it must be centred and levelled precisely over the mark and protected from rain and dust.
• Theodolite: Used where a total station is not available or for high-precision angle work; observations are taken on both faces to remove instrument errors.
• Electronic distance measurer: Distances must be corrected for temperature and pressure, so a thermometer and barometer are carried with it.
• Steel tape: Gives accurate short distances when used at standard tension and corrected for temperature, slope and sag.
• Fibreglass tape: Safer near electricity but stretches more than steel, so it is used only for lower-accuracy measurements.

GNSS equipment

GNSS equipment fixes the coordinates of control points from satellite signals, either in real time or by post-processing. A typical control kit includes a base receiver, a rover, radio or internet links and processing software. Example: a surveyor fixing control for a large ranch in a remote area uses two geodetic receivers in static mode and processes the data in the office.

• Geodetic GNSS receiver: Only survey-grade receivers are used for cadastral control; handheld navigation receivers are not accurate enough.
• GNSS antenna: The antenna height must be measured and recorded at every occupation, since an error in it passes directly into the height of the point.
• Radio modem or GSM link: Range depends on terrain and network coverage, so links are tested before work starts.
• Field controller: Holds the job settings, coordinate system and stored points, so it is backed up daily.
• Processing software: Checks baseline quality and adjusts the network to known control.

Levelling equipment

Levelling equipment gives the heights of control points relative to a benchmark. Example: control points for a water company's land are levelled so pipeline designs use the same datum.

• Automatic level: Its line of sight is checked regularly with the two-peg test.
• Digital level: Removes reading and booking errors but needs charged batteries and a clean bar-code staff.
• Levelling staff: Must be held vertical and kept clean; worn or damaged joints cause reading errors.
• Change plate: Prevents the staff sinking between foresight and backsight.
• Staff bubble: Its adjustment is checked against a plumb line.

Accessories and field equipment

Accessories hold instruments and targets steady and exactly over the survey mark, so faults in them cause errors even with an accurate instrument.

• Tripod: Legs are spread well and pressed firmly into the ground, and clamps are tightened before setting up.
• Tribrach: The plummet is checked regularly, because an out-of-adjustment plummet misplaces every point.
• Prism and prism pole: The prism constant set in the instrument must match the prism used.
• Ranging rods: Held vertical behind the mark to give a clear line of sight.
• Plumb bob: Used when centring in wind-free conditions or to check the optical plummet.
• Hammer and cold chisel: Used to set pins and cut crosses for marks on rock or concrete surfaces.
• Hand-held radios: Speed up fieldwork and improve safety on long lines.

Recording and computing equipment

• Field book: Records must be neat, complete and in ink, since they are legal evidence of the survey.
• Data collector: Data is downloaded and backed up every day.
• Scientific calculator: Used to check angle sums and misclosures before leaving each station.
• Laptop with software: Used for adjustments and for the plans submitted for approval.
• Base maps and control lists: Obtained from the Survey of Kenya before fieldwork.

Materials for control points

Materials are consumed in marking and protecting the new control points so that they can be found and used for many years.

• Cement, sand and ballast: Mixed and cured properly so the beacon does not crack or move.
• Iron pins or rods: Give a sharp, durable centre point that instruments are centred over.
• Pre-cast concrete beacons: Save time in the field and give consistent marks.
• Wooden pegs: Mark points temporarily until permanent beacons are placed.
• Survey nails and paint: Make marks on hard surfaces findable and easy to identify.
• Station description forms: Allow other surveyors to recover the point later.

Procedure for preparing equipment before fieldwork

1. Check the job requirements: Confirm the accuracy class, number of points and method to be used so the right equipment is selected.
2. Assemble the kit: List and gather instruments, accessories, materials and records using a checklist.
3. Inspect each item: Check instruments, tripods, tribrachs and tapes for damage and loose parts.
4. Test and calibrate: Carry out adjustment checks such as plummet, collimation and two-peg tests, and EDM baseline checks.
5. Charge and back up: Charge batteries, clear and back up data collectors and set the correct coordinate system.
6. Pack safely: Pack instruments in their cases and secure them for transport.
7. Record: Note serial numbers, calibration dates and items issued in the equipment register.

Care and maintenance of equipment

• Cleaning: Wipe instruments, prisms and staff with soft cloths and keep lenses free of dust.
• Protection from weather: Use umbrellas and covers in sun and rain, and dry instruments before casing them.
• Safe transport: Carry instruments in padded cases and never on the tripod over long distances.
• Batteries: Charge fully, store at room temperature and replace when they no longer hold charge.
• Regular calibration: Have instruments serviced and calibrated at set intervals and after any knock.
• Storage: Store in a dry, secure store with records of who has each item.

Chapter Summary

This chapter focused on the essential tools, equipment, and materials required for establishing cadastral survey control points, highlighting their specific roles in accurate surveying. It explained how control points are identified using oral points to ensure clear communication and verification. Various methods for establishing cadastral control points were detailed, including traversing, GNSS, triangulation, levelling, and trilateration, each described with their unique procedures and applications. The chapter emphasized the importance of selecting appropriate techniques depending on the survey context and accuracy requirements. Finally, the process of monumenting cadastral survey control points was covered, outlining the standards and materials used to create durable and visible markers that define property boundaries reliably. Overall, the chapter provided a comprehensive guide to establishing precise and legally recognized control points in cadastral surveying.