What is back sight and Fore Sight?

What is back sight and Fore Sight?

h) Back sight : (B.S.) – The first sight taken on a levelling staff held at a point of known elevation. B.S. enables the surveyor to obtain HI +sight i.e. Height of Instrument or line of sight. i) Fore Sight : (F.S.) – It is the last staff reading taken from a setting of the level. It is also termed as minus sight.

What is back sight reading in surveying?

1 surveying : a reading of the leveling rod in its unchanged position when the leveling instrument has been taken to a new position. 2 surveying : a sight directed backward to a previous station.

What is surveying Wye level?

wye level in American English noun. Surveying. an instrument, consisting of a spirit level mounted under and parallel to a telescope, that can be rotated in its Y-shaped supports for adjustment.

What is the fore sight reading?

Fore sight (FS) – short for “fore sight reading”, the last staff reading taken before changing the instrument to the other position. It is the staff reading taken on point whose RL is to determined. This sight is considered as negative and deduced from Height of Instrument to determine RL of the point.

How do you calculate foresight and backsight?

Measure a backsight on A (for example, BS = 1.89 m). Measure on C a foresight FS = 0.72 m. Calculate HI = BS + E(A) = 1.89 m + 100 m = 101.89 m. Find the elevation of turning point C as E(C ) = HI-FS = 101.89 m – 0.72 m = 101.17 m.

What is the meaning of back sight?

backsight in American English 1. a sight on a previously occupied instrument station. 2. ( in leveling) the reading on a rod that is held on a point of known elevation, used in computing the elevation of the instrument.

What is backsight and foresight reading in levelling?

The backsight is the first staff reading taken after the level is set up and leveled at the point. Foresight (FS) or Foresight reading. It is a staff reading taken on a point whose elevation has to be determined through levelling process. It is also known as minus sight.

What is Wye level used for?

A surveyor’s leveling instrument having a telescope and attached spirit level, mounted in Y-shaped supports which permit it to be lifted and reversed, end for end; it is used in the direct measurement of differences in elevation.

What is the difference between a wye level and dumpy level?

The essential difference between the dumpy level and the Wye level is that in the former case the telescope is fixed to the spindle while in the Wye level, the telescope is carried in two vertical Wye supports. The bubble tube may be attached either to the telescope or to the stage carrying the wyes.

What do you mean by back sight orientation?

[′bak‚sīt ′meth·əd] (engineering) A plane-table traversing method in which the table orientation produces the alignment of the alidade on an established map line, the table being rotated until the line of sight is coincident with the corresponding ground line.

What is Backsight distance?

The angle to a line of sight, measured clockwise from (usually) a north meridian. Since a survey progresses from a point of known position to points of unknown position, a backsight is a reading looking “backward” along the line of progress.

When to use an intermediate sight in surveying?

Intermediate Sight. An intermediate sight (I.S) is any staff reading taken on the point of unknown elevation after the back sight and before the fore sight. This is necessary when more than two staff readings are taken from the same position of the instrument. Change Point.

What’s the difference between backsight and foresight in surveying?

As nouns the difference between backsight and foresight is that backsight is the rear sight of a firearm while foresight is the ability to foresee or prepare wisely for the future. What is heighting in surveying? Heighting instruments are used to measure the relative heights and depths of points on the Earth’s surface.

What is the difference between back sight and fore sight?

Back Sight. A back sight (B.S) is the first staff reading taken after setting up the instrument in any position. This will always be a reading on the point of known elevation. Fore Sight. A fore sight (F.S) is the last staff reading taken before moving the instrument. This will always be reading on a point whose elevation is to be determined.

What do you need to know about surveying?

Surveying is the science of determining the relative positions of objects or points on the earth’s surface. These points may be any physical thing: a highway, culvert, ditch, storm drain inlet, or property corner. Distances and directions determine the horizontal positions of these points.