By the end of this chapter, you will be able to:
Mastering these skills will help you work confidently and efficiently in the surveying field, ensuring reliable results and well-maintained equipment.
Operating angle measuring instruments is a fundamental skill for land survey professionals in Kenya, where precise angular measurements underpin accurate mapping, boundary determination, and construction layout. This chapter focuses on the identification and operation of key angle measuring tools used in the field, emphasizing practical competence with instruments such as the total station and compass. Mastery of these instruments ensures surveyors can deliver reliable data critical for land management, infrastructure development, and legal documentation. In Kenya’s diverse terrain and dynamic development contexts, proficient use of these instruments enhances efficiency, accuracy, and professionalism.
Identifying the correct angle measuring instrument is crucial for surveyors to select the right tool for specific tasks, whether for traversing, setting out, or topographic surveys. Kenya's land surveyors encounter various instruments, each with unique features, capabilities, and limitations that affect measurement accuracy and ease of use. This section explores the two primary angle measuring instruments widely employed in Kenyan surveying practice: the total station and the compass. Understanding their specifications and operational contexts enables surveyors to maximize field productivity and data reliability.
Instrument identification means recognising each angle measuring instrument from its parts, markings and features, and knowing the type of angles 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 optical and electronic theodolites, to total stations that measure angles to one second and distances at the same time. Identifying the right instrument for the job saves time and ensures the required accuracy. Example: for a road realignment survey for a sugar company, the team takes a total station for the control traverse and a prismatic compass for a quick reconnaissance of the cane fields beforehand.
| 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 the top, 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 or set direction | Magnetic north |
| Typical accuracy | 1" to 5" | About 15' to 30' |
| Power | Batteries | None |
| Affected by local magnetism | No | Yes |
| Cost | High | Low |
| Typical use | Control, cadastral, engineering and setting out | Reconnaissance, rough traverses, forestry |
The total station is an advanced electronic instrument integrating an electronic theodolite, electronic distance measurement (EDM), and microprocessor for data recording and processing. It is the most versatile angle measuring instrument in modern Kenyan surveying, used extensively by professionals in county governments for cadastral surveys, in urban planning departments, and by private survey firms. Familiarity with its components and functions ensures accurate angular and linear measurements suited for complex survey tasks.
| Name | Specification | Use |
|---|---|---|
| Angle Accuracy | 1" to 5" (seconds of arc) | Determines precision of angular measurements |
| Distance Range | Up to about 5,000 m with a prism; about 500 to 1,000 m reflectorless | Enables measurement over long distances |
| Magnification | 30x to 40x | Allows clear sighting of distant targets |
| Battery Life | 8 to 12 hours | Supports extended fieldwork |
| Data Storage | Internal memory 100,000+ points | Stores survey data for transfer |
Surveyors at a county land office use the total station for property boundary surveys, where angular precision of 1" is essential for legal accuracy. The instrument's EDM allows quick distance measurements, reducing time spent at each survey station.
The compass is a traditional yet vital instrument for measuring horizontal angles, particularly in preliminary surveys, reconnaissance, and areas where electronic instruments are impractical. It remains popular in rural and forested areas of Kenya due to its portability, simplicity, and independence from batteries.
| Name | Specification | Use |
|---|---|---|
| Magnetic Needle | Balanced, pivoted magnet | Indicates magnetic north |
| Graduated Circle | 360 degrees marked in increments | Measures bearings and angles |
| Sighting Mechanism | Sighting vane or prism | Aligns the instrument with targets |
| Leveling Bubble | Spirit level attached | Ensures horizontal positioning |
| Compass Housing | Non-magnetic material | Prevents interference with readings |
In remote agricultural areas, surveyors rely on the prismatic compass to establish property lines where GPS signals are weak. The instrument's ability to provide quick directional bearings supports efficient traversing across large farms.
| Feature | Prismatic compass | Surveyor's compass |
|---|---|---|
| Graduation | Whole circle bearings, 0° to 360° | Quadrantal bearings, 0° to 90° in each quadrant |
| Graduated ring | Fixed to the needle, rotates with it | Fixed to the box, needle moves over it |
| Reading | Through a prism while sighting | Directly from the top after sighting |
| Zero position | South end (graduations inverted for prism reading) | North and south |
| Mounting | Hand-held or on a light tripod | Usually on a tripod or staff |
Create a free account to open more of this chapter.
Free: practical guides, quick cards, workplace scenarios and more.
Create a free accountThis chapter focused on the identification of key angle measuring instruments used in surveying, with particular attention given to the total station and compass. It detailed the specific features and functions of the total station, emphasizing practical exercises to enhance proficiency in its use. The compass was also examined as a fundamental tool for determining directions and measuring horizontal angles. The operational procedures for these instruments were thoroughly discussed, highlighting the steps necessary for accurate angle measurement in the field. Proper maintenance practices were outlined to ensure the longevity and reliability of these instruments, including routine checks and careful handling. Understanding both the technical and practical aspects of these tools is essential for effective surveying work. The chapter integrated theory with hands-on approaches to prepare students for real-world application in various surveying contexts.
At the start of this chapter we promised you would be able to:
Tick each one you can genuinely do.
So, are you there yet?
You're competent when you can confidently do 50% or more of what this chapter promised.
Sign in to record how you're doing.