TACHEOMETRY SURVEYOBJECTIVES:- Produce the topographic map and detailed plan of the proposed area by using surveying software (Theodolite, Total Station) INSTRUMENT REQUIRED:- Total Station or Theodolite Stadia Rod Peg Reflected Prism (i.e. only for total station) Tripod Stand INTRODUCTION:- Tacheometry survey is a branch of surveying in which horizontal and vertical distance of points are obtained by optical measurement avoiding ordinary and slower process of measurement tape. Tacheometric surveys are usually performed to produce contour and details plans for further work, or to produce coordinates for area and volume calculations. Observation are usually performed from known survey stations, often established by traversing. THEORY:- Used a Total Station, able to read distance by reflecting off a prism. It is now possible to produce plans of large areas that previously would have taken weeks, in a matter of days. This instrumentation has facilitated the development of this method of detail and contour surveying into a very slick operation. Used a Theodolite, able to read distance by sighting from instrument at Stadia rods. It is also possible now to detailing but it is slowest process than Total Station. FIELD WORKS FOR TRAVERSING:- a. Reconnaissance: It is done to- To locate suitable positions for stations, poorly executed reconnaissance can result from difficulties at later stages leading waste of time and inaccurate work To obtain overall picture of the area. b. During selection of station following points should be noted Number of station should be kept minimum as possible Length of traverse legs should be kept as long as possible to minimize effect of centering error, however too long leg can also result from refraction error, Station should be located such that they are clearly intervisible Station should be placed on firm, level ground so that the theodolite/total station and tripod are supported adequately during measurement Interior angle of the station between traverse legs should not be less than 30° or should not be around 180° to minimize error during plotting c. Station marking Station marking needs to be done by the permanent marker for easy allocation of station throughout the survey period. Generally for traverse purpose, wooden pegs are flush into the ground, a nail is tapped into the top of peg to define exact position of station A reference or witnessing sketch of the features surrounding each station should be prepared especially if the stations are to be left for any time before used or if they are required again d. Linear measurement of traverse line will normally be measured by EDM or by measuring tape During Linear measurement, for precision both way (forward and backward direction) measurement is carried out and discrepancy should be better than 1:2000 e. For Angular measurement, if the internal angles are being read, it is usual to proceed from station to station round the traverse in an anticlockwise direction Generally, more than one set of reading is preferred for higher accuracy measurement along with both face (right and left face) reading If external angles are observed then one should occupy the stations in a clockwise direction When all internal angles are measured, sum of internal angle should be equal to (2n- 4)*90, for external angle (2n+4)*90, REQUIREMENTS OF FIELD NOTES:- Accuracy: Field data and reference data should be accurately noted Integrity: A single omitted measurement or detail can nullify the use of notes for plotting. So Notes should be checked carefully for completeness before leaving Legibility: Notes can be used only if they are legible. A professional-looking set of notes is likely to be professional in quality Arrangement: Note forms appropriate to the particular survey contribute to accuracy, integrity, and legibility Clarity: Advance planning and proper field procedures are necessary to ensure clarity of sketches and tabulations and to minimize the possibility of mistakes and omission. CONCLUSION:- We know that when the stations have been sighted, a sketch of the traverse should be prepared approximately to scale. The stations are given reference letters or numbers. This greatly assists in planning and checking of field work. RESULT:- Making topographic map and detailed plan of proposed area.