Lateral measurements to chain lines for locating ground features are known as offsets. For this purpose perpendicular or oblique offsets may be taken . If the object to be located (say road) is curved more number of offsets should be taken. For measuring offsets tapes are commonly used. For setting perpendicular offsets any one of the following…
The following points should be considered in selecting station points: (i) It should be visible from at least two or more stations. (ii) As far as possible main lines should run on level ground. (iii) All triangles should be well conditioned (No angle less than 30º). (iv) Main network should have as few lines as possible….
Various technical terms used in connection with the network of the triangles in surveying are explained below: Station: Station is a point of importance at the beginning or at the end of a survey line. Main station: These are the stations at the beginning or at the end of lines forming main skeleton. They are denoted as…
Chain survey is suitable in the following cases: (i) Area to be surveyed is comparatively small (ii) Ground is fairly level (iii) Area is open and (iv) Details to be filled up are simple and less. In chain surveying only linear measurements are made i.e. no angular measurements are made. Since triangle is the only figure…
The following instruments are required for measurements with chain and tape: (i) Arrows (ii) Pegs (iii) Ranging rods and ranging poles (iv) Offset rods (v) Laths (vi) Whites (vii) Plumb bobs and (viii) Line ranger. Arrows When the length of the line to be measured is more than a chain length, there is need to mark…
Measurement of distances using chain or tape is termed as chaining. This is the accurate and commonly employed method in surveying: These instruments can be classified as (i) chain (ii) steel band and (iii) tapes. (i) Chains: The chains are composed of 100 pieces of 4 mm diameter galvanised mild steel wires bent into rings at…
All the distances required for making a plan are the horizontal distances. Hence in the field horizontal distances are measured or sufficient readings are taken to calculate horizontal distances. In this chapter the methods used for linear measurements are explained. Method of preparing a plan using only linear measurements is by conducting chain surveying. METHODS…
In 1960 System International (SI units) unit was approved by the conference of weights and measures. It is an international organisation of which most of the Countries are the members. In this system also unit of linear measurement is metre. However, in this system use of centimetres and decametres are discouraged. Of course major difference between…
As stated in the definition of surveying the objective of measurements is to show relative positions of various objects on paper. Such representations on paper is called plan or map. A plan may be defined as the graphical representation of the features on, near or below the surface of the earth as projected on a…