4.1 Methods of preparing cadastral plan

The preparation of cadastral plans involves multiple approaches, each suited to different survey conditions, client requirements, and regulatory contexts. In Kenya, surveyors must select methods that ensure accuracy, legal validity, and clarity for land registration and dispute resolution. This section examines the principal methods used in the preparation of cadastral plans, highlighting their procedures, tools, and application contexts.

4.1.1 Plane Table Survey Method

The plane table survey method is a classical approach widely used in cadastral surveying, particularly in areas where quick field plotting is advantageous. It allows the surveyor to draw the map directly in the field, facilitating real-time verification of measurements and boundaries.

• Direct plotting: The plane table setup enables the surveyor to plot points on paper as measurements are taken, reducing transcription errors common in other methods.
• Equipment: Consists of a drawing board mounted on a tripod, alidade for sighting, and leveling instruments to ensure horizontal setup.
• Field adaptability: Ideal for relatively small or moderately sized parcels where terrain and accessibility allow for station establishment.
• Accuracy considerations: Requires careful leveling and stable mounting to minimize angular errors; appropriate for surveys demanding moderate precision.
• Legal significance: The plane table method is recognized by the Survey of Kenya and can produce legally admissible cadastral plans when properly executed.

Step-by-step procedure to prepare a cadastral plan using the plane table method:

1. Set up the plane table at a convenient station point and level it carefully using a spirit level.
2. Fix the drawing sheet securely on the board and mark the station point as the origin on the sheet.
3. Orient the plane table using a back sight to a known point or magnetic north for consistent directional reference.
4. Use the alidade to sight boundary points, marking their positions directly on the drawing sheet.
5. Move to the next station point, ensuring overlap with previous plotted points for control and accuracy.
6. Repeat the process until all boundary points are plotted, connecting them to form the cadastral parcel outline.
7. Annotate the drawing with boundary lengths, bearings, and relevant survey data.

4.1.2 Total Station Survey Method

The total station method represents a modern approach to cadastral surveying, combining electronic distance measurement and angle measurement into a single instrument for high precision.

• Integrated measurement: Measures horizontal and vertical angles and distances electronically, reducing manual recording errors.
• Data storage: Capable of storing measurements digitally for later processing, facilitating efficient data management.
• Versatility: Suitable for complex terrains and large parcels, enabling rapid data collection.
• Accuracy: Provides high accuracy, often within millimeters, essential for legal cadastral boundaries.
• Kenyan standards: The use of total stations complies with Survey of Kenya guidelines and is preferred for cadastral surveys requiring precision.

Procedure for preparing a cadastral plan using a total station:

1. Set up the total station instrument over a known control point and level it precisely.
2. Initialize the instrument by entering control point coordinates and orienting the instrument to a reference direction.
3. Measure angles and distances to boundary markers or natural features defining the land parcel.
4. Record the data electronically, ensuring each point is logged with its coordinates.
5. Traverse or resection methods can be used to establish new control points as necessary.
6. Download data to a computer for processing and plotting using CAD software.
7. Generate the cadastral plan with precise coordinates, boundary lines, and annotations.

4.1.3 GPS Survey Method

Global Positioning System (GPS) technology has become prominent in cadastral surveying, offering rapid positioning and mapping capabilities, especially in remote or difficult terrain.

• Satellite-based positioning: Provides geospatial coordinates using signals from multiple satellites.
• Real-Time Kinematic (RTK): Enhances accuracy to centimeter level, suitable for cadastral boundary determination.
• Portability: Lightweight and easy to transport equipment allows for flexible field operations.
• Data integration: Coordinates can be imported into GIS and CAD systems for plan preparation.
• Regulatory compliance: Surveyors must ensure GPS data meets the accuracy and reliability standards set by Survey of Kenya.

Steps to prepare a cadastral plan using GPS:

1. Establish base station at a known control point with fixed coordinates.
2. Set up rover GPS receivers at boundary points to collect coordinate data.
3. Use RTK or post-processing techniques to enhance positional accuracy.
4. Record all point coordinates systematically, ensuring clear identification of boundary markers.
5. Transfer GPS data to survey software for processing.
6. Plot the cadastral parcel using the coordinate data, verifying boundary closure.
7. Annotate the plan with control points, boundary descriptions, and relevant metadata.

4.1.4 Traditional Chain and Compass Survey Method

While largely supplanted by modern technology, the chain and compass method remains relevant in some Kenyan rural areas due to its simplicity and low cost.

• Manual measurement: Uses a surveyor’s chain or tape for distances and compass for bearings.
• Field applicability: Useful for small plots with accessible terrain and where electronic instruments are unavailable.
• Limitations: Lower accuracy due to magnetic declination, chain sag, and human error.
• Legal considerations: Plans prepared by this method must be carefully checked for accuracy to meet legal standards.
• Training value: Provides foundational skills for understanding survey principles.

Procedure for preparing a cadastral plan with chain and compass:

1. Establish a starting point and mark it clearly on the ground.
2. Measure the length of each boundary using a surveyor’s chain or tape, ensuring it is stretched taut.
3. Determine bearings of each boundary line using a compass, correcting for local magnetic declination.
4. Record distances and bearings systematically in a field book.
5. Close the traverse by returning to the starting point, checking for any discrepancies.
6. Plot the traverse on graph paper using the recorded distances and bearings.
7. Verify the plan for accuracy and prepare the final cadastral plan with annotations.

Chapter Summary

This chapter covers the essential methods used in preparing a cadastral plan, emphasizing the step-by-step procedures required for accuracy and compliance with standards. It introduces the various tools, equipment, and materials necessary for the preparation process, including detailed discussions on software such as AutoCAD, ArcGIS, and QGIS, alongside traditional instruments like scale rules, tracing paper, technical drawing pens, protractors, and straight edges. The chapter highlights the importance of precise cadastral data computation to ensure the reliability of measurements and boundary delineations. Finally, it explains the structure and components of a cadastral plan, guiding the learner on how to assemble and present this critical document effectively for legal and administrative use.