Basic Concepts of Surveying (Part 1)
Surveying
- Surveying is defined as the art and science of obtaining quantified and qualified measurements, the interpretation of these measurements and a meaningful presentation of result.
- Surveying is the collection of data or information.
- We are concerned with the surveying of geoinformation:
For engineering projects
For geographical mapping
- In surveying, there is a need for a reference system for fixing relative positions of points.
 |
| Basic Concepts of Surveying (Part 1) |
Examples where Surveying is needed:
- Construction of a building
It includes:-
- Site selection
- Knowledge of topography (Map)
- Planning building on it
- Transfer building onto the site
- Town planning
It includes:-
- Site selection
- Knowledge of topography (Map)
- Planning town on it
- Transfer the town onto the ground
- Euro Tunnel
- Deformation of a dam
- Bridge planning
- The tilt of a tower (Taj Mahal)
- Artillery bombing
- Missile
Explanatory Video
Surveying: Two categories
-
Surveying
Bringing the ground/terrain in laboratory/office for working upon it.
-
Laying out
Taking the work onto the ground as per design specifications.
Reference System for measuring Geoinformation of the Earth Surface
- X-Y plane (it can be used only for a mathematical surface).
- Geoid (everywhere in this surface, the potential is the same).
- MSL or Mean Sea Level (it is a geoid which is the average surface of the sea and it is measured over a period of 19 years).
- Ellipsoid
There are two types of Surveying:
Plane Surveying
- The surveying in which the earth's surface is considered to be flat.
- For a 20 km distance in the x-direction, the difference in distances between the arc and the corresponding chord will only be 10 mm.
- For a 20 km distance in the z-direction (or the geoidal height), the difference in distances between the arc and the corresponding chord will be 16 m which is a significant value.
- Plane surveying can be done for making a planimetric map which is only plotting X and Y (not Z or geoidal height).
- These surveys deal with areas of limited extent (areas less than 200 km2).
- For engineering projects like bridges, factories, dams, canals, railways, highways, etc. plane surveying is done.
Geodetic Surveying
- The surveying in which the earth's curvature is considered.
- A higher degree of precision is exercised in linear and angular measurements in geodetic surveying.
- These surveys extend over large areas (such as a State or a Country).
*Self Typed
*Source- Internet, Books, Self-Analysis