Surveying

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

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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.

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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 :

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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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Precisions for different methods of measuring distances are given below:-

Pacing (ordinary terrain): 1/50 to 1/100

Taping (ordinary steel tape): 1/1000 to 1/10,000.

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Units of measurement used in past and present surveys are

For construction work: feet, inches, fractions of inches (m, mm)
For most surveys: feet, tenths, hundredths, thousandths (m, mm)
For National Geodetic Survey (NGS) control surveys: meters, 0.1, 0.01, 0.001 m
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For surveying, we need to have some prerequisite conditions. If these conditions are not met we can have a huge variation in result. Therefore we have to apply corrections to get the true result.

Ideal Conditions
1) A tape accurate to 0.00305m or 0.01 ft should be used.
2) Tension of the tape should be about 66.7N or 15 lb.
3) Temperature should be determined within 5.56°C or 10°F
4) The slope of the ground, should be within 2 percent

On ground these are nearly impossible to achieve and thus corrections need to be applied.
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We know that earth flattens in the polar direction and this curvature of earth is responsible for the departure of horizontal line from a level surface. To counter this error, orthometric corrections is applied.

This departure in feet, C_f is calculated as
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