Aquaculture Engineering

Unit 1- Surveying

Chain surveying

Definition
Chain surveying is the type of surveying in which linear measurements are made in the field. This type of surveying is suitable for surveys of small extent in open ground to secure the data for exact description of the boundaries of piece of land.

Principles of Chain surveying
The principle of chain survey or chain triangulation is to provide a skeleton or frame work consisting of number of connected triangles, as a triangle is the only simple figure that can be plotted from the lengths of its side measured in the field.

• Survey stations: A survey station is the prominent point on the chain line. If it is at the beginning or at the end of the chain line is known as Main survey station.
• Survey lines: The lines joining the survey stations are called as survey lines. The lines joining the main survey stations are called as main survey lines. The biggest of the main survey lines is called as base line.
• Check lines: Check lines or proof lines are the lines which are run in the field to check the accuracy of the work. The length of the check line measured in the field must agree with its length on the plan. A check line may be laid by joining the apex of the triangle to any point on the opposite side or by joining two points on any two sides of a triangle.

• Tie line: Tie line is a line which joins subsidiary or tie stations on the main line. The main object of running a tie line is to take the details of near by objects but it also serves the purpose of check lines.