BFC 21111 GEOMATICS AND SURVEY CAMP

TRAVERSE1.0 INTRODUCTION

Traversing is a form of a control survey that requires the establishment of a series of station that are linked together by angles and distances. The tools that we use in traversing are total station, prism, peg and tripod. Traversing is normally associated with the field work of measuring angles and distances between points on the ground. Traverse closure and adjustment procedures are used to distribute error in measurements.

The use of traversing surveys is very fundamental and become one of the most common methods in geomatics engineering work such as general purpose angle measurement, provision of control surveys, contour and detail mapping and setting out and construction work. Traverse survey are divided into two types:a) Open traverse

Open traverse are traverse that begin at one coordinate and not ended at any point of coordinate. This type of traverse is rarely used because the accuracy and the survey result are cannot be check.

b) Closed traverse

Closed traverse are traverse that are polygon shaped. This type of traverse are begun and ended at the same point. The basic point of the coordinate to this traverse has to be known. Closed traverse whether loop or connection are commonly use this is because the types of this traverse can be check the accuracy.2.0 OBJECTIVES

1) To expose in field work procedures of establishing horizontal control network.

2) To precisely determine the horizontal locations of all traverse stations.3) To know about the advantages of bearing and their use in various survey works.

4) To computes the coordinates, the area of traverse and the class of traverse.

5) To determine the nature of errors affecting the traverse work.3.0 THEORY

In a traverse, three stations are considered to be of immediate significance.(See Figure 5-1.) These stations are referred to as the rear station, the occupied station, and the forward station. The rear station is that station from which the persons performing the traverse have just moved or a point to which the azimuth is known. The occupied station is the station at which the angle-measuring instrument is set up. The forward station is the next station in succession and is the immediate destination of the party. During the traverse (Figure 5-2), the horizontal angles, vertical angles, and distances are measured. Figure 5-1 : Stations of Immediate significanceFigure 5-2 : Diagram of a traversea. Horizontal Angles. Horizontal angles are determined from instrument readings made at the occupied station by sighting the instrument on the rear station and turning the instrument clockwise to the forward station. When measuring horizontal angles, the instrument is always sighted at the lowest visible point of the station markers designated the rear and forward stations. Horizontal angles are used in determining azimuths.

b. Vertical Angles. Vertical angles are determined from instrument readings made at the occupied station to the height of instrument on the station marker (usually a range pole) at the forward station. When the distance between two successive stations in a traverse exceeds 1,000 meters, the vertical angle must be measured reciprocally (measured from each end of that particular traverse leg). This reciprocal measurement procedure is used to eliminate errors caused by curvature and reflection. Vertical angles are used in determining the difference in height between stations.

c. Distance. The distance between the occupied station and the forward station is measured by using electronic devices, horizontal taping, or trig-traverse procedures. The distance is used in conjunction with the horizontal and vertical angles to determine coordinates and height.

4.0 INSTRUMENT

NoItemsQuantity (set)

1Total Station1

2Prisms2

3Pegs4

4Nails4

5Tripod3

6Hammer1

5.0 PROCEDURE

1. Planning and reconnaissance: suitable traverse station is set in the area. Planned the minimum number of traverse stations. The obstacle that may obstruct the survey work is considered.2. Pegging traverse station: consideration line of sight of each control point and its susceptibility to disturbance.

3. Establish datum: Survey is started with three known control points. Distance to the nearest 10 is measured. If the measurements differ by more than 30mm/ 20 repeat or find other control point.

4. Several steps are followed so it will lead to a smooth traverse.

a) The instrument was set up first.

b) The instrument was levelled and centred.

c) The required datum needs to setup the datum

d) Face left horizontal reading to foresight station (bearing & distance) was recorded

e) The instrument was turned and sight foresight station

f) Face left horizontal reading to foresight station (bearing & distance) was recorded

g) The instrument (from Face Left to Face Right) was transited

h) The required datum (bearing) to back backsight was set.

i) Face left horizontal reading to backsight station (bearing & distance) was recorded

j) Instrument was turned to face foresight station

k) Face left horizontal reading to foresight station was recorded.

l) The mean bearing foresight station was recorded.

m) The instrument to the next station (foresight station) was moved

n) The next traverse line bearing are respect or correspond to the previous mean bearing.

6.0 ANALYSIS OF DATA

7.0 DISCUSSION1. Traversing work has been done to establish a series of station that is linked together by angles and distances. Before doing the traversing work, we have been teach on how to conduct traversing work and there are a few things that must be considered. First ,all screw must be parallel to the centre line. Then tripod stand must be in a straight line with the picket. After setting up, prism and total station must be in a straight line to the picket too. Do not forget to make sure the total station can see prism in other two station. Value from bearing (prismatic compass) must be entered correctly. Distance between one points to others must clearly seen in 40m.

2. The bearing misclosured for our traverse work was 00100. This value was accepted because our bearing misclosured is below 00230. The correction for each station was 00010.3. First traverse survey, we unable to find the accurate value of precision fraction which must be more than 1: 40000. So, we conduct the second survey where we measured the distance between the station by using the measuring tape. Finally, we managed to find out the precision factor 1: 6616.883 where we change the distance between station 4 to 8 from 56.223m to 40.150m.4. We facing a lots of problem during conducting the survey, one of the major problem was the location where we found out the hidden tree ,fences and houses surrounding the location. So this make our work become more difficult because we unable to shoot the prism and to get the accurate value.

8.0 RECOMMENDATION1. There are a few suggestions to reduce error during traversing work.

The picket position must be correctly in same line with total station.

The person who are in charges with setting up equipment must know how to setting up very well.

All reading must be read by one person only for all survey point.

2. Other than that, there are a few suggestion to reduce error during calculate the survey data.

Double check is needed to ensure data was correct and the traverse was closed.

All data observe must be calculated correctly with correct formula.

All the angle and distance must be correctly calculated.

3. The total station must be used carefully because its price is expensive.

9.0 CONCLUSION Traverse is a measurement of straight lines and the horizontal angle from one point to another using total station. The sides can be expressed as either polar coordinates or as rectangular coordinates. For better understanding, the definition of traverse survey can be summarized as a form of control survey that requires the establishment of a series of station that is linked together by angles and distances. Our traversing done successfully. We reach the linear misclosure that is1: 6616.88