Vertical distance measurement leveling Vertical distance measurement Leveling

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Vertical distance measurement (leveling)

Vertical distance measurement (leveling)

Vertical distance measurement • Leveling is the operation of measuring vertical distances, either directly

Vertical distance measurement • Leveling is the operation of measuring vertical distances, either directly or indirectly, to determine differences in elevation.

Vertical distance measurement • The elevation of a point near the surface of the

Vertical distance measurement • The elevation of a point near the surface of the earth is its vertical distance above or below an arbitrarily assumed level surface.

Vertical distance measurement Difference in elevation (vertical distance) may be measured by one of

Vertical distance measurement Difference in elevation (vertical distance) may be measured by one of the following methods: 1. Direct leveling, by measuring vertical distances directly. (most precise & commonly used) 2. Indirect leveling, by measuring vertical angles. 3. Barometric leveling, by measuring the differences in atmospheric pressure. 4. Gravimetric leveling, by measuring the differences in gravity at various stations.

Vertical distance measurement • General Definitions: • Bench mark (B. M. ) is a

Vertical distance measurement • General Definitions: • Bench mark (B. M. ) is a definite point of which the elevation & location of it are known. • Turning point (T. P. ) is an intervening point between two bench marks upon which point foresight and backsight rod readings are taken as a turning point.

Vertical distance measurement • Backsight (B. S. ) is a rod reading taken on

Vertical distance measurement • Backsight (B. S. ) is a rod reading taken on a point of known elevation, as a bench mark or a turning point • Foresight (F. S. ) is a rod reading taken on a point the elevation of which is to be determined, as on a turning point.

Vertical distance measurement • The height of instrument (H. I. ) is the elevation

Vertical distance measurement • The height of instrument (H. I. ) is the elevation of the line of sight of the telescope above the datum when the instrument is leveled. • The datum most commonly used is mean sea level.