Information that you may know

TRAVERSE

Traverse is the  position of   a point  on the ground that may be established if its bearing  and distsnce from another known point are measured .

Close traverse :
If the traverse proceed  from one coordinate  point to another it is known as  a closed  traverse. A closed traverse may therefore close back  on to its starting point or any  other    co-ordinate point. It is thus capable of being checked and adjusted to fit  accurately between these known  points.

Open traverse :
An open traverse  on the other hand does not close  on to a known point . it cannot be easily checked  nor can it be properly  adjusted and it is a form of traverse which should only be used in exceptional circumstance.






  • Open Traverse

·         In surveying, a traverse that does not close back upon itself or on another point of known position. As such, it does not provide a means of checking for errors.
·         a surveying traverse that fails to terminate where it began and therefore does not completely enclose a polygon
·         An open traverse originates from a point whose position may be known or unknown but terminates to a point whose position is not known. In this type of traverse, computational check is not possible to detect error or blunder in distances or directions. To minimize error, repeated observations for measurements need to be taken. In Figure consider a traverse ABCDE that originates from the point A which may be unknown or may be defined with reference to known point P lying on the line PQ of known azimuth, but it terminates to an unknown point E. Thus, traverse ABCDE is an open traverse. An open traverse is generally used for exploratory purpose such as mine surveying.


Purpose of Traversing :
        i.            For surveying detail. A traverse  network of survey lines and ground marks provides a system of control points which can be accurately plotted on a map or  plan. The  position of the artificial and natural features are  located on the ground  relatively to this network and  these details  can then be plotted in their proper position  by reference to the  plotted  traverse  lines and stations.
      ii.            For setting out. The position of roads, buildings and other new construction  can be established  by the surveyor relatively to the traverse control points  from  information  supplied by the designer, architect or engineer. Pegs can then be set out  on the ground  from the traverse  to define  the  position of  such new works.



TACHEOMETRY

            Tacheometry is an direct method of distance measurement to get the horizontal and vertical distance. Thus, the horizontal (x y coordinates) and vertical (reduced level) positions, of points on the each surface relatively to one another are determined simultaneously without using a chain or tape or a separate levelling instrument.

The word of  ‘tacheometry’ is derived from the Greek Tacns,meaning ‘swift’ and metrot meaning ‘ a measured’ or (quick measurement). Distance measurement can be carried out rapidly since it is an indirect method even on irregular earth surface or any obstacle.
tacheometric method

Tacheometris surveying is divided into 2 system; Optical Distance Measurement ( ODM ) and Electromagnetic Distance Measurement ( EDM ). 

·         Before starting  tacheometry, it is important to know the Rl of the point that we are using.
  • Control survey is carried out first by traversing for horizontal cpntrol and levelling for vertical control.
  • Detail survey involves extraction of the surrounding features nearby the station such as trees, fences, building, etc.
  • Set up total station on the station in the control network and set RO. Measure instrument height (Hi) and target height (Ht) of the observed features (center of the prism(reflector)).
  • Data to be collected for detail surveying using total station are horizontal and vertical angles, horizontal and slope distances.
  • All collected for detail must be booked or recorded. The type of detail should be noted in the booking form.
  • Repeat the process for other observation (control) stations.





SOLAR OBSERVATION


Survey traverses shall be in a closed circuit for quality checking. The traverse lines can be closed back to its starting point or closed to the existing boundary marks. Traversing lines shall be controlled by solar observation .
Solar observation field is used when to get true meridian orientation ,to control cumulative errors in traversing .This solar observation only can be carry out in the morning and evening .Distance between observation station to RO should not less than 30m and Sun altitude must be 10 to 30 degree .



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