By the end of this chapter, you will be able to:
Mastering these skills ensures you can confidently handle essential tools that help create precise and reliable survey results in your trade.
Operating angle measuring instruments is a fundamental skill for land survey professionals in Kenya, where accurate angular measurements underpin tasks such as boundary delineation, construction staking, and topographic mapping. These instruments enable surveyors to capture precise horizontal and vertical angles critical for creating reliable site plans and ensuring compliance with legal land descriptions. Mastery of both traditional and modern angle measuring equipment, including total stations and compasses, enhances efficiency and accuracy in diverse field conditions encountered across Kenya’s varied terrain.
Identifying the appropriate angle measuring instrument is crucial for effective land surveying. Different instruments serve distinct purposes depending on the precision required, environmental conditions, and nature of the survey. Kenyan surveyors often balance the use of advanced electronic devices with traditional tools to meet project demands, from county government cadastral surveys to agricultural land assessments.
Instrument identification means recognising each angle measuring instrument from its parts, markings and features, and knowing the type of angle it measures, its accuracy and the work it suits. Angle measuring instruments range from simple magnetic compasses that give bearings to about half a degree, through theodolites, to total stations that measure angles to one second and distances at the same time. Example: before a road survey for a county roads department, the survey team takes a prismatic compass for a quick reconnaissance walk and a total station for the main traverse.
| Name | Specification | Use |
|---|---|---|
| Total station | Electronic theodolite with EDM, angle accuracy 1" to 5" | Precise horizontal and vertical angles with distances |
| Electronic (digital) theodolite | Digital angle display, accuracy 1" to 20" | Horizontal and vertical angles without distance |
| Optical theodolite | Glass circles read through a microscope, 1" to 20" | Angles where electronic instruments are not used |
| Prismatic compass | Whole circle bearing ring read through a prism, about 15' to 30' | Reconnaissance, rough traverses and detail |
| Surveyor's compass | Quadrantal graduation read from above, about 15' | Bearings in simple traverses |
| Clinometer | Pendulum or bubble with degree scale | Measuring slopes and vertical angles roughly |
| Feature | Total station | Compass |
|---|---|---|
| What it measures | Horizontal and vertical angles plus distance | Magnetic bearing of a line |
| Reference direction | Any chosen backsight | Magnetic north |
| Typical accuracy | 1" to 5" | About 15' to 30' |
| Power | Batteries | None |
| Affected by local magnetism | No | Yes |
| Cost | High | Low |
The total station is a sophisticated electronic instrument integrating an electronic theodolite with an electronic distance meter (EDM). It measures horizontal and vertical angles alongside distances, providing comprehensive data for three-dimensional positioning. In Kenya, total stations are widely used in urban development projects, infrastructure planning, and detailed topographic surveys because of their accuracy and data integration capabilities.
| Name | Specification | Use |
|---|---|---|
| Angle accuracy | 1" to 5" | Precision of angle measurement |
| Distance range | Up to about 5,000 m with a prism; about 500 to 1,000 m reflectorless | Measuring short and long distances |
| Telescope magnification | About 30x | Sighting distant targets |
| Memory | Tens of thousands of points or more | Storing field data |
| Battery life | About 8 to 12 hours | Full day of fieldwork |
Total stations can be programmed to perform complex tasks such as stakeout, area calculation, and coordinate geometry (COGO) computations. They facilitate rapid data collection and integration with Geographic Information Systems (GIS), enhancing survey workflows for projects like Nairobi County urban planning.
Total stations reduce human error, improve productivity, and provide versatile measurement capabilities suitable for diverse environments, from flat agricultural lands to hilly regions around Mount Kenya.
The compass is a traditional instrument used to determine direction relative to the Earth's magnetic poles. It is essential for preliminary surveys, orientation, and in situations where electronic devices are impractical due to power limitations or environmental constraints. In rural areas and community land mapping exercises, compasses remain valuable for Kenyan surveyors.
| Feature | Prismatic compass | Surveyor's compass |
|---|---|---|
| Graduation | Whole circle bearings, 0° to 360° | Quadrantal bearings, 0° to 90° in each quadrant |
| Graduated ring | Attached to the needle, rotates with it | Fixed to the box; needle moves over it |
| Reading | Through a prism while sighting | Directly from above after sighting |
| Mounting | Hand-held or on a light tripod | Usually on a tripod or staff |
The compass is limited by local magnetic attraction and lower accuracy, but its low cost, simplicity and independence from power keep it useful for many tasks in Kenya.
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Create a free accountThis chapter focused on identifying key angle measuring instruments used in surveying, specifically the total station and the compass. The total station was examined as an advanced electronic device combining distance measurement and angle calculation, while the compass was discussed as a simpler tool for determining direction based on magnetic north. The chapter then explored practical exercises for operating these instruments to accurately measure angles in the field, emphasizing correct handling and reading techniques. It also highlighted the importance of regular maintenance to ensure the instruments remain precise and reliable, covering cleaning, calibration, and safe storage practices. Understanding the proper use and upkeep of these tools is essential for effective surveying and obtaining accurate data. The chapter provided a clear foundation for students to confidently operate and care for angle measuring instruments in various surveying scenarios.
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