Surveying

  Tape T apes is linear distance measuring instrument. Tapes are made of many materials and have the advantage of being light weight and providing greater precision. They cannot stand very rough handling as can chains. They can be divided into four classes according to the materials of which they made, such as follows: Cloth or linen tape Metallic tape Steel tape Invar tape Cloth or linen Tape: Tape made of cloth or linen can be termed as the cloth or linen tape. Generally this type of tapes used for the offset measurements. Due to their tendency to stretch easily, twist, and shrink when wet it is not used for the other measurements of high precision required. cloth tapes are available in lengths of 10m, 20m, 25m, 30m (10m to 30m) and in feet; 33ft., 50ft., 66ft., 100ft. One end of the tape is provided with small brass ring whose length is included in the total length of the tape. Metallic Tape: Metallic tape is made up of metallic wire provided with metallic ring. Since metallic tape

  Chain  Chains are the linear distance measuring instrument used in surveying. Chains are formed by the 100 links of 4mm galvanized mild steel wire. These links are connected by 3 circular or oval wire rings. These rings between links provide the flexibility to the chains.  chain are available in both metric and foot system. At the both end chain is provided with brass handle having swivel joint which make easy to roll or unroll the chain without twisting and knots. At 10th link chain is provided with a tally of one teeth, 20th link with a tally of two teeth and so on till 40th link with tally of four teeth and at the center of the chain is provided with a circular tally. For every meter circular brass ring is used as tally. These tallies are provided for the easy reading of measurements.      fig. Chain       fig.  Tally Types of Chains used in Surveying: Depending upon the length of the chain and unit system these are divide into following types, Metric chains Gunter's chain or

  Survey Instruments and concepts    Ranging Instruments   1.      Signals and Ranging Rod . 1.a.    Pegs: G enerally, pegs are made up of wood. The Size of pegs depends on the type of survey work They are used for, and the type of soil they have to drive in. The peg should be driven vertically into the soil & the top portion should be visible clearly. pegs are the exact point from which the measurements are to be taken or over which an instrument is to be set. A nail or brass stud is driven into the flat top of the peg for permanent mark. Markers may be also used for very Temporary marks. Generally, pegs are;  1) Made of Timber or steel  2) used to mark the position of stations.  3) pegs are in length of 15 cm to 60cm (depends up on nature of ground)                   1.b.    Ranging Rod : It is surveying Instrument which is used to mark the position of a station and to set out straight lines on the field. It's Also used for ranging

  Unit 4     Theodolite Traversing: 4.1 Traverse Definition, Purpose, Types and Equipment Traversing is that type of survey in which no. of connected survey lines form a framework and the direction or angle of survey lines are measured with an angle measurement instrument   like theodolite, total station and the length of the line are measured with tape or EDM (Electronic Distance Measurement). Theodolite traversing is a type of survey in which direction or angle of survey lines are measured with theodolite and length by tape. A traverse is a series of connected straight lines of known length, each joining two points on the ground and related to one another by known angles between the lines. Straight lines between the consecutive stations are traverse legs. And the points defining end of traverse lines are traverse station. There are two types of traverse: 1) Closed traverse a) Geometrically closed and b) Linked traverse 2) Open Traverse   1) Closed traverse A t