Levelling: A Fundamental Surveying Technique for Civil Engineers

Introduction

Levelling is a surveying technique used to determine the relative heights of different points on the Earth’s surface. It is a fundamental skill for civil engineers, as it is used in a variety of applications, including:

• Setting out the levels of buildings and other structures
• Designing roads and railways
• Surveying land for development
• Monitoring the movement of the ground

Definition of Levelling

Levelling is the process of determining the difference in elevation between two or more points. This is done by using a level, which is an instrument that is used to establish a horizontal line of sight. The level is set up on a tripod, and the line of sight is then directed at a staff, which is a graduated rod that is held vertically on the ground. The staff reading is then taken, and this gives the elevation of the ground at that point.

Benchmarks

Benchmarks are points of known elevation that are used as reference points for levelling. They are typically established by government agencies, such as the U.S. Geological Survey. Benchmarks are used to ensure that the levels that are taken during a levelling survey are accurate.

Equipment Used for Levelling

The following equipment is typically used for levelling:

• Level: A level is an instrument that is used to establish a horizontal line of sight. There are two main types of levels: optical levels and digital levels. Optical levels are less expensive than digital levels, but they are also less accurate. Digital levels are more accurate than optical levels, but they are also more expensive.
• Staff: A staff is a graduated rod that is held vertically on the ground. Staffs are typically made of wood or fiberglass, and they are graduated in feet or meters.
• Tripod: A tripod is a three-legged stand that is used to support the level. Tripods are typically made of aluminum or wood.

How to Do a Simple Land Level

The following is a step-by-step guide to conducting a simple land level:

1. Set up the level on a tripod.
2. Level the level using the leveling screws.
3. Sight the staff on the first point.
4. Take the staff reading.
5. Move the level to the second point.
6. Sight the staff on the second point.
7. Take the staff reading.
8. Subtract the first staff reading from the second staff reading to determine the difference in elevation between the two points.

Levelling is a fundamental surveying technique that is used by civil engineers to determine the relative heights of different points on the Earth’s surface. It is a relatively simple process, but it is important to follow the correct procedures to ensure that the levels that are taken are accurate.