The purpose of Surveying is to accurately define your boundaries! Above and below the ground.
Purpose of levelling in surveying
Levelling is done to make the field even.
Say you’ve an empty place and want to build a home. If you do not carry out levelling on the site, your building may not be perfectly vertical because of small undulations which is not visible to the bare eyes. This is a critical part in Structural Design. How? Let me explain…
The building structural design is done assuming that the area is totally plane and hence the forces are also calculated accordingly. You know that pure vertical is 90 degrees.
If your land is not perfectly level, then the forces may act at inclined angles like 87/92 degrees. The forces also change with the deviation and when such forces get accumulated, over a period of time, your structure may fail.
The latest instrument used is Total Station. An electronically operated device which uses a concept of optics. The device sends out a laser signal which will be reflected back by a reflector which is placed anywhere. Based on parameters like time, angle etc. The horizontal and vertical distances are calculated. Additionally, you can also prepare a contour map using a Total Station which can then be used in various drafting softwares like AutoCAD.