Table of Contents

## How do you calculate collimation error?

The collimation error is compensated by multiplying the correction by the BS and FS length difference and adding it to the elevation difference. This requires the length of each sight be captured as the readings are taken.

**What is the collimation error?**

The error in alignment between the optical axis of a telescope and the declination axis of its equatorial mount; the two should be exactly perpendicular if the telescope is to track stars precisely.

### How do you calculate reduced level by collimation?

The height of collimation is obtained by adding the staﬀ reading, which must be back sight to the known reduced level of the point on which the staﬀ stands. Reduced levels of all the other points are obtained by subtracting the staﬀ reading from the height of collimation.

**What is collimation level?**

Height of Collimation is the height of the horizontal plane through the telescope. In order to see the staff on the BM the instrument must be higher. To find the Height of Collimation (Instrument Height) add the staff reading to the level of the Bench Mark. Height of Collimation = BM + staff reading.

#### What formula is used in arithmetic check in height of collimation method?

Arithmetic check for Collimation Method: Sum of B.S. – Sum of F.S. = last R.L. – First R.L.

**How do you calculate the height of 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.

## Which type of the collimation error is eliminated?

In differential leveling, the effect of a level’s collimation error can be almost entirely eliminated by carefully balancing the foresight length with the backsight length.

**How do you find the height of collimation?**

### How do you calculate 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 a collimation level?**

In levelling, a method of calculating reduced levels by subtracting staff readings from the level of the line of sight (collimation line) of the instrument. This method is usually favoured where it is required to obtain the levels of many points from one set-up.

#### How do you calculate height of collimation?

**How is backsight and foresight calculated?**

## What is collimation test in surveying?

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.

**What is a two peg test?**

Two Peg Test. All instruments are subject to errors. The checking of the instrument (level) is therefore important. The main error is where the line of sight is not parallel to the horizontal line of collimation. In this case your levels will not be correct. A test for checking the level is known as the two peg test.

### How do you set the level of collimation?

Establish 2 points approximately 50 metres apart on level ground as shown below. Set the level half way between the 2 points. Take the 2 staff readings. In our example an error will exists (line of sight does not coincide with line of collimation).

**Why is my line of sight not parallel to collimation?**

line of sight is not parallel to the horizontal line of collimation. In this case your levels will not be correct. A test for checking the level is known as the two peg test. This test determines the amount of error and if an error occurs notify the technician (the level must be serviced).

#### How do I perform a peg test on my instrument?

Each group will be required to perform a peg test to check the instrument. Each person in the group should record the results of the Peg Test in their own field book. Set out and mark on the ground (with wooden pegs driven into the Earth, or roofing nails in tar) two point some 30 m apart.