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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