Difference between Plane Surveying and Geodetic Surveying

Saad Iqbal | 🗓️Modified: February 24, 2022 | ⏳Time to read:6 min

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:

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

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However, primarily classification of surveying includes:

1. Plane Surveying
2. Geodetic Surveying

The difference between there two classification is given below:

• Plane Surveying:

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:

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.

Also Read: Chain Surveying  –  Principles of Chain Surveying

Difference between Plane Surveying and Geodetic Surveying in tabular form:

Conclusions:

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.

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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.

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