Classilication of Survey

This Earth is not a full sphere, but a Oblate Spheriod, which is flattened like an orange at the poles. The length of the Earth's Polar axis is 1271383 km and the Equatorial Axis is 1275678 km (according to Sir Hayford). Thus, the polar axis is 42.95 km shorter than the equatorial axis. If we do not pay attention to the roughness of the top surface of the land, then the top surface of the shell is in the curve. Therefore, the distance we measure between the two points is not the curved surface of the spheroid, rather than the pure horizontal, which is obviously somewhat greater than the horizontal distance. Similarly, the curvature of the ground surface also has an effect on the relative elevation of the points.
 On the basis of this fact, the survey of the earth is divided into the following two parts.
(i) Plane Survey
(ii) Geodetic Survey

(i) Level survey-

In this survey, the curvature of the earth is ignored and the terrain is assumed to be flat. A flat survey is considered sufficient for surveying small terrain, because on the surface of the earth, due to curvature there is a difference of only one cm in a distance of 12 km, which is very less.
 Flat survey is adopted for small areas and works of lesser importance. Generally, an area of ​​up to 260 sq km is considered a small area. The authority level survey is adopted for engineering works. It takes less time and the outlay is not too high.

(ii) Geodetic Survey

In this type of survey, the full appearance and curvature of the earth is taken care of and all the lines on the ground surface are considered to be curved.
  More precise instruments and methods are used for surface survey and angular measurements are taken in place of linear measurements and Spherical Trigonometry is used for calculations. Horizontal and horizontal control stations are established at sufficient distance in the context of survey, in respect of which survey work of lesser importance is done. This survey is very time consuming and expendable.
 All countries determine their borders with the survey of land.
Bhupastha survey is also called Trigonometrical Survey. This survey in India is conducted by the Survey of India Department.
 Other grounds for survey classification are:
(a) Land Based Survey
(b) Purpose Based Survey
(c) Instruments Based Survey
(d) Method-Employed Survey

1. Area Based Surveys - 

These are as follows
(i) Topographical Survey - This survey is done for the natural features of the terrain, such as mountains, rivers, rivulets, mounds, lakes, forests and human figures, such as cities, villages, roads, canals, railways, bridges, etc. This is done to find the position and size. The position of the objects in this survey is determined by linear and angular measurements.
(ii) Land Ownership or Cadastral Survey - This survey is done to determine the boundaries of cities, regions, states and to find the area of ​​land covered under it.
(iii) City Survey - This survey is done to find the information and status of roads, drains, pipe lines, sewers and buildings and open areas within the city.
(iv) Hydrographic or Marine Survey - This survey is done to find out the extent, depth, speed, discharge, etc. in rivers, canals, reservoirs, lakes, oceans. In order to obtain data regarding navigation, dock work, dam construction, irrigation, water supply, flood etc., hydrographic survey is necessary.
(v) Aerial Survey - This survey is done by aircraft to get information about flood, earthquake, drought, damaged dam affected areas and other geographical views. In areas where land is difficult to reach by means of land, aerial survey is also adopted for the survey there.
(vi) Astronomical Survey - In this survey, the absolute position of the points / lines on the earth is determined by reference to the planets of the sky.

2. Objective based survey - 

These are as follows

(i) Engineering Survey - This survey is done to collect the necessary data for the preparation and design of any construction work, such as a canal, road, bridge, dam, etc.
(ii) Hydrological Survey - This survey is done to get information about availability, quantity, type and extent etc. of surface and ground water.
(iii) Geological Survey - This survey is done to get information about the composition of rocks and other substances located below the surface of the Earth. Construction of tigers and tunnels and laying of underground railways requires geological survey.
(iv) Mine Survey - Mine survey is done to find out the extent of mineral deposits located below the ground, like coal, oil, natural gas etc.
(v) Archaeological Survey - Underground old objects,
This survey is done to find the signs and remains.
(vi) Military Survey - The survey which is done to find the position of important marks, points, bases, routes, bridges, rates, etc. in military vision is called a military survey.

3. Survey based on equipment-

Following are the types of survey based on the equipment used for survey work or the method adopted.
(i) Reconnaissance Survey
(ii) Chain Survey
(iii) Compass Survey
(iv) Plane Table Survey
(v) Theodolite Survey
(vi) Tachometric Survey
(vii) Survey by modern instruments (electronic instrument-distance measurement meter, total station etc.)
(viii) Photographic Survey

4. Method Based Survey - 

It consists of following two systems.

(i) Triangulation Survey
(ii) Traversing Survey