Guide to Surveying

Errors in Chaining | Guide to Surveying and Levelling

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Types of Errors occurring in Chain Surveying

There are two types of Errors that are commonly seen to occur in Chain Surveying. For students studying the concept of Chain Surveying, study of the occurrence of different types of Errors in Chain Surveying is important. In this article, we will briefly discuss different types of Errors in Chain Surveying and the situations in which they occur.

Types of Errors:

  1. Cumulative error
  2. Compensative error

Cumulative error

These errors always accumulate in one direction and are serious in nature. They affect the survey work considerably.

They make measurements too long or too short.

These errors are of two types and are known as systematic errors.

They are classified as follows:

  1. Positive error
  2. Negative error

Positive error

These errors make the measured length more than the actual length which results into wrong calculations by the Surveyor.

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Different Methods for the Calculation of Areas in Surveying

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Different methods for the calculation of Areas in the field of Surveying

In this article, we will list out different methods to calculate the areas in Surveying and also study each of the method in depth… We will also explain each method with a suitable example for your better understanding…

Here are the five important rules (Methods) used for the calculation of areas in Surveying:

  1. Midpoint ordinate rule
  2. Average ordinate rule
  3. Simpson’s rule
  4. Trapezoidal rule
  5. Graphical rule

We will now move on with our discussion on the first rule “Midpoint ordinate rule” with a suitable example.

Midpoint-ordinate rule

The rule states that if the sum of all the ordinates taken at midpoints of each division multiplied by the length of the base line having the ordinates (9 divided by number of equal parts).

Midpoint ordinate rule | Method for calculating area in Surveying
Midpoint ordinate rule | Method for calculating area in Surveying

In this, base line AB is divided into equal parts and the ordinates are measured in the midpoints of each division.

Area = ([O1 +O2 + O3 + …..+ On]*L)/n

L = length of baseline

n = number of equal parts, the baseline is divided

d = common distance between the ordinates

Example of the area calculation by midpoint ordinate rule

The following perpendicular offsets were taken at 10m interval from a survey line to an irregular boundary line. The ordinates are measured at midpoint of the division are 10, 13, 17, 16, 19, 21, 20 and 18m. Calculate the are enclosed by the midpoint ordinate rule.

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Types of Measurements in Surveying | Civil Engineering

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Types of Measurements in Surveying

Surveying is the art of making suitable measurements in horizontal or vertical planes. This is one of the important subjects of civil engineering. Without taking a survey of the plot where the construction is to be carried out, the work cannot begin.

From the above definition, we conclude on two types of measurements in surveying. They are as follows:

  1. Linear measurements
  2. Angular measurements

Now we will go on with the discussion of each of these types of measurements along with their subtypes.

Linear measurements are further classified as follows:

Horizontal Distance

Vertical Distance

Horizontal Distance

A horizontal distance is measured in horizontal plane if a distance is measured along a slope, it is reduced to its horizontal equivalent.

Horizontal Angle
Horizontal Angle

Vertical Distance

A vertical distance is measured along the direction of gravity at that point. The vertical distance are measured to determine difference in elevations in various points.

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Introduction to Surveying | Civil Engineering

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Surveying

Surveying is the art of making suitable measurements in horizontal or vertical planes. This is one of the important subjects of civil engineering. Without taking a survey of the plot where the construction is to be carried out, the work cannot begin.

Surveying Chart
Surveying Chart

Levelling

Levelling is the art of representing relative positions in the vertical plane of different points on the earth’s surface.

It helps in determining the areas that are to be levelled to achieve a certain slope.

Principles of Surveying

All the surveys that are conducted are based on two fundamental principles. They are as follows:

  1. Working from whole to part
  2. Fixing a point with reference to two fixed points

Working from whole to part

In order to localize errors and prevent their accumulation, a set of control points is always established with great precision first for the whole area to be surveyed.

Later on, details or filled in between these control points to a relatively smaller precision.

This fundamental work principle is known as “Working from whole to part”.

Fixing a point with reference to two fixed points

Survey stations are fixed by atleast two measurements, either both linear or angular measurements or linear and angular measurements from two control points.

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