Survey leveling- III
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The document discusses leveling, which is the process of finding the difference in elevation between two points on Earth. A level, which contains a telescope and spirit level, and a leveling staff are used to establish a horizontal plane from which elevation measurements can be made. The staff has an "E" pattern for easy reading through a telescope and is made of materials like aluminum with telescopic sections. Factors like the curvature of Earth must be taken into account for level readings over long distances, as the ground surface is curved while horizontal lines are straight.
Survey leveling- III
- 1. A line from any point on the earth to the center of the earth A vertical line, established by a pointed metal bob hanging on a string Curved surface, at any point, is perpendicular to a plumb line Vertical distance from a datum to a point on the earth Process of finding the difference in elevation of points on the earth Marked point of known elevation from which other elevations maybe established
- 2. The process of finding the difference in elevation between two points. A level (a telescope with crosshairs attached to a spirit level) and a leveling staff (held vertically) are used. By keeping the level bubble centered in the vial, the horizontal crosshair in the telescope can be kept on the same elevation while the telescope turns in any direction in the horizontal plane. It establishes a horizontal plane in space from which measurements can be made on the staff.
- 3. • The "E" pattern is designed for easy reading when seen through a telescope. • Staff is a large ruler, available in lengths of 3, 4 or 5 metres and usually made of aluminium with telescopic sections.
- 4. • If a level sight is made on a level staff 1 mile away from any point on the earth, the reading, would be greater by 0.667 ft because of the curvature of the earth. • The departure of the earth from the horizontal line varies as the square of the distance from the level to the staff. • a level surface is a curved surface and • a horizontal line is a straight line.Recall, 𝐶 = 0.667𝑀2
- 6. The Surveying Handbook, Russell C. Brinker & Roy Minnick. OPENMAPS SURVEYORS RESOURCES