Surveying is that the art of ascertaining or determining the comparative positions of various objects on the surface of the earth by measuring the horizontal distance between them,and by preparing a map to any suitable scale.
Thus, during this discipline, the measurements are taken only within the horizontal plane.
Levelling is that the art of determining the relative vertical distance of various points on the surface of the earth. Therefore, in Levelling, the measurements are taken only within the vertical plane.
Object Of Surveying
The aim of surveying is to make a map to point out the relative positions of the objects on the surface of earth. The map is drawn to some suitable scale.
It’s shows the natural features of a country, like towns, villages, roads, railway, rivers etc. Maps can also include details of various engineering works, like roads, railways, irrigation canals, etc.
General Principal Of Surveying
The general principles of surveying are given below:
✓ To work from the entire to the part, and
✓ To locate a new station by a minimum of two measurements (linear or angular) from fixed reference points.
1. consistent with the primary principle, the entire area is first enclosed by main stations (i.e. controlling stations) and main survey lines (i.e. controlling lines).
The realm is then divided into variety of parts by forming well-conditioned triangles.
An almost equiangular triangle is taken into account the most effective well-conditioned triangle.
The most survey lines are measured very accurately with a regular chain.
Then the edges of the triangles are measured. the aim of this process of working is to stop accumulation of error.
During this procedure, if there’s any error within the measurement of any side of a triangle then it’ll not affect the entire work.
The error can always be detected and eliminated.
But, if the reverse process (i.e. from the part to the whole) is followed then the minor errors in measurement are going to be magnified within the process of expansion and a stage will come when these errors will become absolutely uncontrollable.
2. consistent with the second principle, the new stations should be fixed by a minimum of two measurements (linear or angular) from fixed reference points.
Linear measurements check with horizontal distances measured by chain or tape.
And the angular measurements inquire the magnetic bearing or horizontal angle taken by a prismatic compass or theodolite.
And in chain surveying the whereabouts of main stations and directions of main survey lines are fixed by tie lines and check lines.
Use Of Surveying
Surveying could also be used for the subsequent various applications:—
1. To make a topographical map which shows the hills, valleys, rivers, villages and towns, forecast, etc. of a rustic .
2. To make a cadastral map showing the boundaries of the fields, houses and other properties.
3. To make an engineering map which shows the small print of engineering works like roads, railways, reservoirs, irrigation canals, etc.
4. To make a geological map showing areas including underground resources.
Classification Of Surveying
Surveying is primarily classified as under:
1. Plane surveying
2. Geodetic surveying.
1. Plan Surveying
As we know that, the shape of earth is spheroidal. Thus, the surface of the earth is clearly curved.
But in plane surveying, the curvature of the earth isn’t taken into consideration.
This is often because the plane surveying is administered over alittle area.
So, the surface of earth is taken into account plane. In such surveying, a line joining any two points is taken into account straight.
The Triangle formed by any three points is taken into account a plane triangle the angles of the Triangle are assumed to be plane angles.
Plane surveying is conducted by state agencies just like the irrigation department, railway department, etc. Plane surveying is completed on a region of less than 250 Sq. Km
2. Geodetic Surveying
Here in the geodetic surveying, the curvature of the world is taken into consideration. it’s extended over an outsized area.
The line joining any two points is taken into account a curved line.
The Triangle formed by any two points is taken into account spherical and therefore the angles of the Triangle are assumed to be spherical angles.
Geodetic surveying is conducted by the survey of India department, and is administered over a region exceeding 250sq. Km.
Secondary Classification Of Surveying
1. based on instruments
✓ Compass surveying
✓ Plane table surveying
✓ Theodolite surveying
✓ Tacheometric surveying and
✓ Photographic surveying
2. based on methods
✓ Triangulation surveying and
3. based on objects
✓ Geological surveying
✓ Mine surveying
✓ Archeological surveying
✓ Military Surveying
4. based on Nature of fields
✓ Land Surveying
✓ Marine surveying
✓ Astronomical surveying