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Compare Direct and Indirect Contouring Methods

The Comparison of Direct and Indirect Contouring Methods is shown below in tabular form

S No Direct Method Indirect Method
1 Very tedious Not tedious
2 Accurate Less accurate
3 Slow Fast
4 Requires more resources Requires less resources
5 Suitable for contouring of small area. Suitable for large areas
6 Points are physically located on the

ground

Points are interpolated in the office

We at engineeringcivil.com are thankful to Mr Ramasesh Iyer for submitting this useful information to us.

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How to determine Area of Field using Cross Staff Survey?

Object: – To determine area of field using cross staff survey.

Equipments:
1. Ranging rod – 7 Nos.
2. 30 m Chain – 1 Nos.
3. Arrow – 5 Nos.
4. Metallic tape (30m) – 1 Nos.
5. Cross staff with stand – 1 Nos.

Procedure: –
1. Field work
2. Classroom work

(1.) Field work
1. First of all first ranging rod is established at point A and makes fixed station taking measurement revising point A to two permanent structures.
2. Second ranging rod is established at point B and for makes fixed station taking measurement revising point B to two permanent structures.
3. Established grid line A to B using ranging procedure by judgment of eye and laying chain on it.
4. Remaining ranging rod established at point P, Q, R, and S, T on right and left side of the grid line and its may be point of permanent structure at different location.
5. Sight point P perpendicular to grid line using cross staff, let’s meeting point is P’ on grid line.
6. Measure distance of AP’ and PP’ by chain (on grid line) and metallic tape (between P to P’).
7. Write all observation in field book or level book immediately.
8. Repeat Sighting procedure using cross staff, let’s meeting point is Q’, R’, S’, and T’ on grid line.
9. Measure distance of AQ’, AR’, AS’ and AT’ by chain (on grid line) and QQ’, RR’, SS’, TT’ using Metallic tape respectively.
10. Write all observation in field book or level book respectively.
11. When complete all observation removes all ranging rods and packed in its cover.

(2) Classroom work: –
1. Draw a complete figure in field book using field observation.
2. Draw a line meeting point P to S and R to T on field book or level book.
3. Calculate the area of field by subtract out side (remaining) area of meeting line in total area in field book

Observation table: –
Area of Field using Cross Staff Survey

Figure: –
Area of Field using Cross Staff Survey-2

Precautions: –
1. The ranging rod should be established correctly state at all points.
2. The judgment of line should be taking correctly during established ranging rod at a point.
3. Distance between surveyor’s eye and reference station (eg. A, B and C) should be minimum one meter.
4. The cross staff should be states during sight both station and observations take accurately.

We are thankful to Er. Praveen Kumar Pandey for submitting this very useful topic to us.

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How to Plot Building Block by the use of Cross Staff?

Object: – Plotting building block by the use of cross staff.

Equipments: –
1. Ranging rod – 3 Nos.
2. 30 m Chain – 1 Nos.
3. Arrow – 5 Nos.
4. Metallic tape (30m) – 1 Nos.
5. Cross staff with stand – 1 Nos.

Procedure: –
1. First of all first ranging rod is established at point A and makes fixed station taking measurement revising point A to two permanent structures.
2. Second ranging rod is established at point B and for makes fixed station taking measurement revising point B to two permanent structures.
3. Established grid line A to B using ranging procedure by judgment of eye and laying chain on it.
4. Remaining ranging rod established at exiting corner of object and sight by open cross staff. Let’s meeting point is P.
5. Measure distance of AP and P to sighted object by chain (on grid line) and metallic tape (between P to sighted object).
6. Next object sighted by cross staff in both directions to grid line.
7. Distance between objects to meeting point is noted in field as well as on grid line.
8. Repeat the process until completion the work.
9. Plot plan of field condition or building block by help of field observation.

Observation table: –
Plot Building Block by the use of Cross Staff

Figure:
Plot Building Block by the use of Cross Staff-2

Precautions: –
1. The ranging rod should be established correctly state at all points.
2. The judgment of line should be taking correctly during established ranging rod at a point.
3. Distance between surveyor’s eye and reference station (eg. A, B and C) should be minimum one meter.
4. The cross staff should be states during sight both station and observations take accurately.

We are thankful to Er. Praveen Kumar Pandey for submitting this very useful topic to us.

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Ranging and Fixing Of Survey Station

The object of this experiment is to set up a survey station. This is the basic step of surveying but this is also the one which has the maximum number of errors.

The Equipments used for this are :-

1. Ranging rod …………5 Nos. (min).
2. 30 m Chain…………..1 Nos.
3. Arrow…………………5 Nos. (min.)

The Procedure to conduct is as follow :

(Ranging by eye)
1. First of all first ranging rod is established at known point A and its ranging rod should be fixed at point A up to completion of work.

2. Second ranging rod is established at known point B (or at known object) and a ranging rod should be fixed at point B up to completion of work.

3. Third ranging rod established at point P (or any) approximately on the line of point AB (by judgment) and it’s not greater than one chain length from point A.

4. Measure the distance of AP by chain and move ranging rod at point P to its next position and establishing a wooden peg or arrow at point P.

5. Third ranging is established at point Q (or any) approximately on the line of point AB (by judgment) and it’s not greater than one chain length from point P.

6. Measure the distance of PQ by chain and move ranging rod at point Q to its next position and establishing a wooden peg or arrow at point Q.

7. Its procedure repeats up to reaching point B.

8. Third ranging rod is established at known point C (or at known object) and a ranging rod should be fixed at point C up to completion of work.

9. Fourth ranging rod established at point P’ (or any) approximately on the line of point BC (by judgment) and it’s not greater than one chain length from point B.

10. Measure the distance of BP’ by chain and move ranging rod at point P’ to its next position and establishing a wooden peg or arrow at point P’.

11. Fourth ranging is established at point Q’ (or any) approximately on the line of point BC (by judgment) and it’s not greater than one chain length from point P’.

12. Measure the distance of P’Q’ by chain and move ranging rod at point Q’ to its next position and establishing a wooden peg or arrow at point Q’.

13. Its procedure repeats up to reaching point C.

14. Fifth ranging rod established at point P” (or any) approximately on the line of point CA (by judgment) and it’s not greater than one chain length from point C.

15. Measure the distance of CP” by chain and move ranging rod at point P” to its next position and establishing a wooden peg or arrow at point P”.

16. Fifth ranging is established at point Q” (or any) approximately on the line of point CA (by judgment) and it’s not greater than one chain length from point P”.

17. Measure the distance of P”Q” by chain and move ranging rod at point Q” to its next position and establishing a wooden peg or arrow at point Q”.

18. Its procedure repeats up to reaching point A.

19. Finally complete a triangle and position of point A, B, and C is known respect to each other.

observation-table

figure-surverying

Precautions: –
1. The ranging rod should be established correctly state at all points.
2. The judgment of line should be taking correctly during established ranging rod at a point.
3. Distance between surveyor’s eye and reference station (eg. A, B and C) should be minimum one meter.

We are thankful to Mr Praveen Kumar Pandey for this very useful article and we hope to see more such contributions.

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What is Photogrammetry?

Photogrammetry is a technique used in surveying to measure the three dimensional coordinates with the help of photography. It is used for the purpose of measurements.

Fundamental Principle
Triangulation is the fundamental principle used by photogrammetry. In this technique, we take photographs from atleast two different locations. The purpose of taking pictures from more than 2 points is to create what engineers call “lines of sight.” Once these lines of sight are prepared, we join them to locate a point where they meet and thus calculate the coordinates of the desired point.
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