What is collimation method?

What is collimation method?

The collimation method is the height-of-instrument method of leveling whereby fore-and-aft readings are made on a leveling staff by an instrument placed intermediately so that the rise or fall between the fore station and the back station is shown by a change in the staff reading. See Also: rise and fall.

What are the methods of Levelling?

The various methods of levelling are as follows:

• Simple levelling.
• Differential levelling.
• Profile levelling.
• Fly levelling.
• Check levelling.
• Reciprocal levelling.
• Trigonometrical levelling.
• Precise levelling.

How do you calculate collimation?

To find the Height of Collimation (Instrument Height) add the staff reading to the level of the Bench Mark. The survey station is below the horizontal plane through the instrument, so to find reduced level, or ground height, take the staff reading away from Height of Collimation.

How is a rise and fall cost adjustment made?

A rise and fall contract allows for fluctuations in the cost of labour, materials and other costs during construction. Where the contract is a lump sum, the change is made to the lump sum amount payable. Then were the contract is a rate schedule agreement, the adjustment is made in the table of rates.

What is HI method?

Height of instrument method deals with obtaining the RL of the line of collimation by adding BS reading of a point whose RL is known. The RL of line of collimation is called Height of Instrument. From this, the staff readings of all intermediate stations is subtracted to get the RL at those points.

How do you read a dumpy level?

Steps

1. Set your tripod up near the spot you want to measure.
2. Connect your device to the tripod and position it over 2 leveling screws.
3. Level the device by adjusting the 2 leveling screws.
4. Turn your telescope 90 degrees and adjust the third leveling screw.
5. Check your level’s calibration by turning it 180 degrees.

What is Levelling Staff least count?

5 mm

How do you read staff leveling?

The staff reading is the reading on the staff at which the horizontal hair appears to cut the staff. A staff reading consists of 4 digits. The first digit represents the whole number of meters, the second digit represents decimeters, and the third, and fourth digits represent millimeters.

How many types of leveling staff are there?

The following three types of self reading staffs are available: (a) Solid staff: It is a single piece of 3 m. (b) Folding staff: A staff of two pieces each of 2 m which can be folded one over the other. (c) Telescopic staff: A staff of 3 pieces with upper one solid and lower two hollow.

What is the use of Levelling staff?

A level staff, also called levelling rod, is a graduated wooden or aluminium rod, used with a levelling instrument to determine the difference in height between points or heights of points above a vertical datum. It cannot be used without a leveling instrument.

How many types of leveling are there?

4 ways

What is the height of Levelling staff?

Levelling staffs are usually 2 to 5 m long, foldable or telescopic, and made of plastic-coated wood or aluminium. Self-reading levelling staffs are usually graduated in metres, decimetres, and centimetres. These graduations are upside-down so that you can read them with a telescope.

What is an RL in surveying?

From Wikipedia, the free encyclopedia. Relative level in surveying refers to equating elevations of survey points with reference to a common assumed datum. It is a vertical distance between survey point and adopted datum plane.

How do you calculate level?

Measuring the height of ground points Differences in height between two points are usually measured with a device called a level . It is called a level because it gives a true horizontal line . The height of each point is then measured by its vertical distance above or below this horizontal line.

How do you calculate RL in surveying?

The difference between the sum of the back sights and the sum of the fore sights should be equal to the difference of the first and the last R.Ls i.e. Σ B.S. – Σ F.S. = Last R.L. -First R.L. This check verifies the calculation of R.Ls. of the planes of collimation and of the change points only.

What is HI in leveling?

Differential Leveling. Definitions. Height of instrument (HI) – the elevation of the line of. sight of the telescope. Starting point.

What does RL level mean?

Reduced level

What is TBM level?

Temporary Bench Mark (TBM) – a point of known height above a pre-defined level. The height of any target point is referred to as Reduced Level (RL), because it is reduced to a known datum.

What is the aim of leveling?

Levelling is a process of determining the height of one level relative to another. It is used in surveying to establish the elevation of a point relative to a datum, or to establish a point at a given elevation relative to a datum.

What is GTS bench mark?

A G.T.S. (Great Trigonometrical Survey) benchmark is a permanently fixed reference survey station (or point), having known elevation with respect to a standard datum (mean sea level). These are established all over India by Survey of India department with greater precision.

How is TBM level calculated?

TBM 2 = 7.96m The value of TBM 2 was 7.96m, the new backsight reading was 0.29m, giving an instrument height of 8.25m (TBM + BS = IH). A number of foresights were then taken within the survey area and these readings were then subtracted from the instrument height to give a real/reduced level.

How do you set a benchmark elevation?

The height of the level is simply the height of the benchmark of known elevation added to the backsight reading of Rod 1.

1. HI (Height of the Instrument) = 100 ft + 5 ft = 105 ft.
2. Elevation of middle point = 105 ft – 6 ft = 99 ft.
3. Elevation of new benchmark = 4.5 ft – 7.5 ft + 99 ft = 96 ft.

What is Rise and Fall method?

Rise and Fall Method is the method of calculating the difference in elevation between consecutive points in levelling work. Some of the points you have to know before starting numerical are: Back sights: The first reading after seeing the instrument is called back sights.

Why is it called a dumpy level?

In 1832, English civil engineer and inventor William Gravatt, who was commissioned to examine a scheme for the South Eastern Railway’s route from London to Dover, became frustrated with the slow and cumbersome operation of the “Y” level during the survey work, and devised the more transportable easier to use “dumpy” …