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DETAIL SURVEY - Coggle Diagram

- - - - Details are measured from a control point (station) that is closest to the area to be mapped
      - provide hori & verti distances at accuracies suitable for detail surveys
      - Distances obtained by tacheometry are of low order accuracy, therefore, is suitable to be used for producing plans at scales less than 1 : 200
      - Fieldwork
        
        Select one of the adjacent station as the reference object (RO) and if possible set the horizontal angle to zero ; all angles will be relative to this RO
        
        When the staff is at a point of detail, observe and record the three stadia hairs, horizontal and vertical angles (nearest 1minute is sufficient)
        
        Set-up instrument over station & record the height of instrument (height of the trunnion axis from the ground)
        
        The procedure is repeated for all details needed and as a precautionary measure, it is sensible to check the reading to the RO from time to time
    - - Details are measured either using an EDM mounted on a theodolite or a total station (EDM+theodolite+on-board software)
      - This method of picking-up details is closely
        linked to computer-aided mapping
      - Recap : EDM is an electronic distance measurement method that is capable of providing horizontal and vertical distances at high accuracies
      - Data observed are normally entered or downloaded to computers and processed using an engineering surveying software to produce the required plans