general notes.pdf - Topographical Survey Definition This is...

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Page 1 of 29 Engineering Surveying 1B 2020 Topographical Survey Definition This is a type of Survey carried out to determine or measure the accurate positions of both natural and man-made features on the surface of the Earth. The features include; Rivers Streams Lakes Hills Roads Canals Railway lines Towns buildings Villages etc Topographic Survey: a survey of selected natural and artificial features of a part of the earth’s surface to determine horizontal and vertical spatial relations. A Topographic Survey gathers data about the coordinates and elevations of points on a piece of land and presents them as contour lines on a plot. The data can be used to create spot height maps, contour maps, or more complex terrain profiles. Topographic maps aim at giving as true representation of the terrain as is possible within the limits of scale, showing both natural and man- made elements on the earth’s surface . These elements are identified and shown in correct position. The Purpose of Topographic Survey The purpose of a topographic survey is to collect survey data about the natural and man-made features of the land, as well as its elevations. Topographic maps are used to show elevations and grading features for architects, engineers, and building contractors. Objectives of Topographical surveys 1. To map topographic features and generate topographical maps and cross sectional profiles 2. To establish the controls for accurately defining locations within project area and production of contours 3. To carry out detailed topographical survey by collecting X, Y and Z OF topo features and spot heights
Page 2 of 29 Engineering Surveying 1B 2020 4. To measure changes in elevation or terrain between different locations of project area 5. To establish/ determine horizontal and vertical control points using ordinary levels using traversing and leveling methods 6. To produce topo cadastral maps of the project area using collected data Specification and Accuracy Levels Accuracy refers to the degree of perfection obtained in measurement of a quantity. It denotes how close a given measurement is to the true value of the quantity Accuracy requirement for topographical surveying depends on; the scale to which the topo maps are to be produced the accuracy of control point surveyed in the field the accuracy to which control points marked in the aerial photographs should match with the same control points on the ground As users of topo maps, we expect high accuracy of topographic maps. The process of building controls should produce points of high accuracy levels as the control points are the basis reference for all the topographic surveying measurements The accuracy levels for topographic surveying vary depending on the scale to which the topo map is to be produced.

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