 # 5 DIFFERENCE BETWEEN PLANE TABLE SURVEY AND GEODETIC SURVEY

Surveys ;Are a method of gathering information from individuals.

A survey ,is a data collection tool used to gather information about individuals.

SURVEYING;Is the science of gathering, determining, recording, and measuring the relative size of human –man-made and natural features on the earth’s surface.

## Definition of Surveying or land surveying :

Is the technique, profession, and science of accurately determining the terrestrial or three-dimensional position of points and the distances and angles between them, commonly practiced by surveyors, and members of various engineering professions.

The measurements involves that of

– Distance,

– Angle and

– Height on the earth’s surface and the result give data which is used for making accurate plan and map.

## TYPES OF SURVEY

There two main types of survey

### Geodetic  Survey:

Is the branch of survey in which when taking measurements,the curvature of the earth is taken into consideration.

Geodetic surveying is the survey in which the curvature of the earth is taken into account and higher degree of accuracy in linear and angular observations is achieved.

The geodetic surveys extend over large areas and lines connecting any two points on the surface of the earth are treated as arcs.

### Plane  Survey

Is the branch of survey which is taken without consideration of the earth curvature

Plane surveying is the survey in which the earth surface is assumed to be plane and the curvature of the earth is ignored.

The plane surveys extend only over small areas and the lines connecting any two points on the surface of the earth are treated as straight lines and the angles between such lines are taken as plane angles.

Other types of survey that overlap with Geodetic and Plane surveying  include s the following;

### Topographical surveying

Is the types of surveying which deals with  measurements of physical features of the earth’s  surface, either natural or man made .

Is the types of survey which  deal with the measurements of boundaries. Example boundaries of towns,villages,districts,regions Countries etc.

### Engineering  Surveying

Is the surveying types which is undertaken to provide special information for construction projects.

NB: Topographical surveying, cadestral Surveying and Engineering surveying  can be either GEODETIC  or PLANE SURVEYING.

## Difference between Plane surveys and   Geodetic Surveys

Plane surveys are the most commonly practised method of surveying and treat the earth as a flat or “plane” surface. Good enough for small-scale surveys in limited areas, the curvature of the earth has no effect on the results, thus the computations and results can be referenced to a plane or flat surface.

Geodetic Surveys are surveys, which take into account the true shape of the earth.

Geodetic surveys are typically carried out with great precision, often over long distances, and are used not only to determine the size, shape and gravity field of the earth.

the table below summarizes the difference between plane table survey and geodetic survey

 Plane Surveying Geodetic Surveying The curvature of the earth is not taken in to consideration In this curvature of earth is considered. In plane Surveying, line joining any two points of triangle formed by any three points is considered as straight line and plane triangle are assumed to be plane angles. In geodetic surveying line joining two points of triangle formed by three points is considered as curved line of spherical triangle and angles of triangle are considered as spherical angles. This survey is done on smaller area less than 250km2 This survey is done on large area greater than 250 km2 Required accuracy is competitively low. High accuracy is required Simple methods and instruments can be used as the required accuracy is low. Very refined methods and instruments are used. 