Height of Collimation and Rise and Fall Method | Methods of Levelling

Methods of Levelling | Guide to Surveying and Levelling

In this article, we will discuss two important methods of Levelling. We will also study these Methods with the help of Numerical Examples in our successive articles.

There are two Methods of Levelling:

  1. Height of Collimation Method
  2. Rise and Fall Method

Height of Collimation Method

This method is simple and easy.

Reduction of levels is easy.

Visualization is not necessary regarding the nature of the ground.

There is no check for intermediate sight readings;

This method is generally used where more number of readings can be taken with less number of change points for constructional work and profile levellings.

Read moreHeight of Collimation and Rise and Fall Method | Methods of Levelling

Chaining on Sloping Ground | Guide to Surveying and Levelling

Chaining on Sloping Ground | Surveying and Levelling

There are two methods for determining horizontal distance on sloping ground.

  1. Direct Method
  2. Indirect Method

Direct Method of Chain Surveying

This method is also known as “Stepping Method”.

The horizontal distances are directly measured by the process of stepping.

Procedure

A path of chain or tape is stretched out from ‘P’.

The path length of chain or tape depends on the steepness of the ground.

The follower holds the zero end of the chain at ‘P’ and directs the leader at P1 to be in the line of PQ and stretch the chain or tape above the ground in horizontal line.

Direct Method | Chain Surveying
Direct Method | Chain Surveying

The leader then transfers the point ‘P1’ to P2 on the ground by means of plumb bob or dropping a pebble or an arrow,

Now the followers take the new position ‘P2’ and directs the leader to move forward and stretch the tape or chain in a line of PQ.

Now the followers take the new position ‘P2’ and directs the leader to move forward and stretch the tape or chain in a line of PQ and the new position is P3.

Again the leader transfers the point P3 to P4 on the ground as done earlier.

This process is repeated till the point Q is reached.

Horizontal distance PQ = S1 + S2 + S3 + S4 + S5

Read moreChaining on Sloping Ground | Guide to Surveying and Levelling

Methods of Calculation of Areas in Surveying | Simpson’s Rule

Calculation of Areas in Surveying | Simpson’s Rule

In one of my previous articles, I discussed Midpoint Ordinate Rule and Average Ordinate Rule in detail with an example and listed out various important methods used for the calculation of areas in Surveying. In this article, we will deal with the next important method (rule) i.e. Simpson’s Rule along with a numerical example used for the calculation of areas in the field of Surveying.

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

Simpson’s Rule

Statement

It states that, sum of first and last ordinates has to be done. Add twice the sum of remaining odd ordinates and four times the sum of remaining even ordinates. Multiply to this total sum by 1/3rd of the common distance between the ordinates which gives the required area.

Where O1, O2, O3, …. On are the lengths of the ordinates

d = common distance

n = number of divisions

Note:

This rule is applicable only if ordinates are odd, i.e. even number of divisions.

If the number of ordinates are even, the area of last division maybe calculated separated and added to the result obtained by applying Simpson’s rule to two remaining ordinates.

Read moreMethods of Calculation of Areas in Surveying | Simpson’s Rule

Contour Analysis | Guide to Surveying and Levelling

Importance of Contouring in the field of Surveying

Contouring is an imaginary line on the ground obtained by joining points having same elevation.

Characteristics of Contours

Contour lines are closed, however they may be close on the map itself or outside the map depending upon the topography.

The spacing between contour lines depends upon the slope of the ground.

In steep slopes, the spacing is small, for gentle slopes the spacing is large.

If the contour lines are equally spaced, they indicate uniform slope.

Contour Analysis
Contour Analysis

If the contour lines are parallel, straight or equally placed, they represent plane surface.

In a series of contour lines on the plan or map indicates either a hill or depression.

In case of the hill, the values of the elevation go on increasing towards the centre whereas in case of depression, the values go on decreasing towards the centre.

Read moreContour Analysis | Guide to Surveying and Levelling