Principles of Surveying

The main purpose of Civil Engineering survey is it to define the position of various points relative to one another. This position can be used for various purposes like keeping the structures exactly where they are supposed to be, defining proper positions of object etc. As these positions are relative so different people may define them differently which can be dangerous at later stages. This makes the surveying a very diverse in nature. However, just like any other thing. It is possible to define certain basic principles which are common for a Civil Engineering Survey and study the different type of surveys. These principles of surveying are very vital for carrying out an accurate civil engineer survey.

The theoretical definition of surveying is as follow:

Surveying is the art of determining relative positions of objects on the surface of earth by taking measurements in the horizontal and vertical planes..

Civil Engineering Survey

The meaning of the word “Survey” is closely looking anything and observing or examining it. So, clearly, it is a very broad term. But we are discussing Civil Engineering Survey. So from now on Survey will mean Civil Engineering Survey. In Surveying we assume the position of the point and find the location of all the other required points with reference to that chosen point. This chosen reference  may be entirely based on imagination or as per some standards. However, It is often required that the survey work is needed to be reproduced or used by other people. So in order to avoid any difficulty in understanding certain principles are defined. These are called as the principles of surveying.

Types of Survey

Civil Engineering Survey is classified in as the basis whether we are taking account of the curve of earth or not. So, depending on it the Surveying is classified into two main classes: 1. Plane Surveying and 2. Geodetic Surveying. One can easily interpret that Geodetic surveys are relevant only when points considered extends over a large area and higher degree of accuracy is also required.

Surveys are also classified in a lot of other ways. So, there are following types of surveyTypes of Survey

  1. Types of survey according to Instrument Used:
    1. Chain Survey
    2. Compass Survey
    3. Plane Table Survey
    4. Theodolite Survey, etc.
  2. Types of survey based on purpose of survey
    1. Mine Survey (to explore minerals)
    2. Geological Survey (to determine different states in earth’s crust)
    3. Archaeological Survey (to trace customs or relics of the past)
    4. Military Survey (to determine points of strategic importance)
  3. Types of survey based on the method used.
    1. Triangulation Survey
    2. Traverse Survey
  4. Types of survey based on place of work
    1. Land Survey
      1. Topographical Survey
      2. Cadastral Survey
      3. City Survey
      4. Engineering Survey
    2. Hydrographical or Marine survey
    3. Aerial survey (in air)

Principles of Surveying

 

While determining the relative position of the points the following two points should be kept in mind.

1.Determining Suitable method for locating a point

It is advised as well as practicable in the field to select at least two points in the field and measure  the distance between them. Using these two points one can determine any other point in the field.

2. Working from Whole to part

It is also advised to first establish the control points with great precision and then various details should be located based on them. Details near to the control point should be located based on them. This way error doesn’t get transferred from different control points and also doesn’t get accumulated. On another hand, If we work from parts to whole the error will keep on magnifying and may get uncontrolable at the end.

3. Provision of Initial framework

This process is often known as providing control. It is essential to ensure that the positions of the control points are known to a higher order of accuracy than those of the subsidiary points. By satisfying this principle it is possible to ensure that errors, which inevitably occur, do not accumulate but are contained within the control framework.

4. Planning

Planning is so obvious principle that it often get ignored. However, it is essential to plan any survey before just rushing into the field with instruments. A proper planning can decrease the cost of surveying and it can also make it more benefiting and economical. It can also make the surveying fun.

5. Checking

The accuracy of a survey is of key importance in any survey. One should work to minimize the error in the calculation and various check should also be done. Basic check like measuring diagonals of a quadrilateral, distances in both directions, angles using different parts of the theodolite circle, leveling booking cross-checks.

6. Safe Keeping

Keeping the information of data obtained from surveying is of keen importance and it should be preserved so that it can be used at a later stage. It is also advised an abstract sheet should be attached with surveying data that summarizes the results and important point obtained from surveying.


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