Surveying is preliminary divided into plane surveying and geodetic surveying on the basis of considering earth surface as a spherical or plane. But there’re more differences between plane and geodetic surveying so let’s explore some of these:
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Different types of surveying
Survey is the art of determining relative position of object on the surface of the earth by taking measurement in horizontal and vertical planes. Its main objective is to take point so that its plan or map can be made. It is considered as the backbone of civil engineering projects and used in almost all type of projects like construction of roads, buildings, bridges, reservoirs, dams, irrigation project etc.,
Generally, survey is classified based on:
- Instrument used: Chain survey, compass survey, plan table survey, theodolite survey etc.
- Purpose of Survey: Mine survey, Geological survey, Archeological survey and mine survey.
- Method Employed: Triangulation Survey, Traverse Survey
- Place of Work: Land Survey, Marine Survey, Aerial Survey
However, primarily classification of surveying includes:
- Plane Surveying
- Geodetic Surveying
The difference between there two classification is given below:
Plane surveying is the type of surveying, in which curvature of earth is not taken into consideration. This type of survey is used when the area to be surveyed is small and usually less than 250 square km. In this type of surveying, as curvature of earth is not considered therefore all measurements or calculations are done by considering surface of earth as a plane or flat surface.
In order to take measurement in such type of survey, triangles are formed on the ground, and for calculating different points these triangles are assumed as plane. Therefore, calculation principle is same as like of plane triangles. Usually, this method is less precise, and errors are involved in it, and error induced in this method is directly proportional to area employed. Plane survey is mostly employed in construction of roads, highways, canals, and landing fields.
Geodetic surveying, also called as trigonometric surveying, is the type of surveying in which curvature of earth is taken into consideration and is mostly used when area to be surveyed is large and more than 250 square km. Geodetic surveying is done with great precision to find out shape, size, and gravity field of earth. Its main objective is to provide control points to which small surveys can be carried out.
In order to take measurement in such type of surveying, all the triangles formed on ground is assumed as spherical and all lines lying on earth surface are assumed as curved lines. High precise instruments are used for taking measurements and spherical trigonometric method is used for calculations.
Difference between Plane Surveying and Geodetic Surveying in tabular form:
|Plane Surveying||Geodetic Surveying|
|Mean surface of earth is considered as plane.||Mean surface of earth is considered as spherical.
|The lines formed by joining two points is considered as plane.
|The lines formed by joining two points is considered as curved.
|Length of line up to 12 km is taken as plane surveying
|Length of line more than 12 km is taken as geodetic surveying.|
|Triangle formed in plane surveying is considered as plane
|Triangle formed in geodetic surveying is considered as spherical.|
|Effect of spherical nature of earth’s surface is not considered in this type of surveying.
|Effect of spherical nature of earth’s surface is considered in this type of surveying.|
|Plane trigonometry is involved for taking calculations
|Spherical trigonometry is used for taking calculations|
|This type of surveying is used when area to be surveyed is less than 250 square km.
|This type of surveying is used when area to be surveyed is more than 250 square km.|
|Measurement is taken by using instruments like chain, measuring tape and theodolite.
|Measurement is taken by high precise instruments like EDM and GPS|
|Because of instrument employed, this type of survey is less precise and has low degree of accuracy.
|This type of survey is highly precise and has high degree of accuracy because of highly precise instruments used|
|Stations formed in this type of surveying are at low distances to each other.
|Stations formed in this type of surveying are at huge distances to each other.|
|This type of surveying is used in general civil engineering project work.
|This type of surveying is done to determine precise location of distant points.|
|It can be done by individual organization or firm
|It can be done by government departments.|
|It is economical and simple method of surveying.
|It is costly and complex method of surveying.|
We know that surface of our earth is oblate spheroid in which length of polar axis is shorter than equatorial axis, but difference is very small. So, earth surface is assumed as spherical and therefore surveying is preliminary divided into plane surveying and geodetic surveying on the basis of considering earth surface as a spherical or plane.
If earth surface is considered as spherical than it will be geodetic surveying which will be employed for area more than 250 square km. It is highly precise and high degree of surveying in which more precise instruments like GPS, EDM are used, and calculations are done by using spherical trigonometry. Its main objective is to determine precise position of object on the surface of earth.
While if spherical nature of earth surface is not considered then it will be called as plane surveying which is employed for area less than 250 square km. Instruments used in this surveying are chains, measuring tape and theodolite therefore, it is less precise and accuracy level is also of low degree. This type of surveying is more employed in construction projects like construction of roads, highways, building and in landing fields.