ENGG Chain Survey

survey station

A survey station in chain surveying is defined as the beginning point or end point. Types

field book

All observations and measurements taken during chain surveying are to be recorded in the standard field book

Tie line

Connects two tie stations Checks the accuracy of fieldwork Helps in taking additional interior details which are far away from chain lines

main station

Main stations: are the end of lines which command the boundaries of survey and the line joining main stations are called main survey line or chain lines.

Chains

Measure distance when very great accuracy is not required Replaced by tape Chain is easily read and easily repaired in the field if broken Weight is a disadvantage when the chain has to be suspended. Only measurements are taken in the field and rest work such as plotting, calculation etc. are done in the office. No angular measurements are made.

Check line/Proof line:

Provided to check the accuracy of field work and plotting work since it is quite evident that length of line on ground should agree with its corresponding length on paper

Subsidiary/Tie stations

Subsidiary/Tie stations: are the point selected on the main survey lines, where it is necessary to locate the interior detail such as fence, buildings etc. These helps in running additional lines to locate the details which are away from the main survey lines

Base Line

The main imaginary line running east and west and crossing a principal meridian at a definite point; used by surveyors for reference in locating and describing land under the rectangular (government) survey system of legal description.

Principle of chain surveying

To prepare a framework or network of triangles because a triangle is a figure which can be plotted on paper by measuring its sides only Formation of well conditioned triangle (no angle greater than 120 degree and smaller than 30 degree) Triangles formed should resemble to the shape of an equilateral triangle.

Offsets

Lateral measurements from the base line to fix the positions of the different objects of the work with respect to base line (check line) Cross staff and optical square is used to set 90 degree in the field