Route Survey Of The Stretch Of Road From Oriawo Along Ogbomoso Road, Oyo To School Of Science, Sabo Oyo Town, Atiba Local Government Area, Oyo State

CHAPTER FOUR
4.0      DATA PROCESSING AND RESULT ANALYSIS
    This involved calculations that are based on acquired data from the field observation to determine locations, direction, height, distance and area etc. some specific formulae were employed for each data set depending on the desired end products and great degree of precision was required.
4.1    FIELD BOOKS REDUCTIONS
    Every field book was reduced to generate the final data set to be used in the final computation
4.1.1    HORIZONTAL ANGLE REDUCTION
    These procedures were adopted in the angular reductions. The face left reading taken to the back station (L1) was deducted from the face left reading to the fore station (L2) to obtain the angle between the lines on face left. Then the face right reading to the back station (R1) was also deducted from the face right reading to the fore station (R2) to obtain the angle between the lines on face right. The mean of those two angles becomes the angle at that station for the horizontal circle reading. Since EDM was used for the linear distance measurement, the vertical angle was not read because it is meant for the correction of linear distance in which the EDM had taken care of. 
The reductions of angles were done by using the formula below.
L2-L1 and R2-R1
Where L2 = (face left of fore sight)
    L1 = (face left of back sight)
    R2= (face right of fore sight)
    R1= (face right of back sight)
L2-L1 =L
R2-R1 =R
            L+R = Horizontal circle reading
              2

4.1.2    VERTICAL ANGLE REDUCTION
As for vertical angle determinations, these were necessary to correct the measured linear distances for slope error. The observations and readings were taken at the same time as the horizontal angular observations were done. They were also deduced as explained below.
L2-90º or 90º- L2 and 270º-R2 or R2-270º (where “L” and “R” indicate angle on face left and face right respectively).
4.1.3    LINEAR MEASUREMENT REDUCTION
The linear distance measurement was carried out with the use of an electronic distance measuring instrument (LeicaTC600), which reduced the slow rate of observation by using linen tape and automatically correct for slope error and calibration constant to provide a true horizontal distance between stations.
The following corrections were applied:
(1) Slope correction
This was applied to the distances using
C   =   ­ L (1– Cos Ø)
Where C = slope correction
L = measured distance
Ø = slope angle
Note: Slope correction is always negative (-)
4.2    COMPUTATIONS
This pertained to the numerical calculation based upon the observed recorded and derived data’s to determine location, areas, volume, direction, heights etc.