Field Procedure for Laying Out a Simple Curve Aaaaa

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 O | Before proceeding to the designated survey site, the lab instructor should be consulted with respect to the following curve elements which will be needed to define the circular curve to be laid out: a
| adius of the curve (
b
| ntersection or deflection angle (
c
| tationing of the point of intersection (P
2 | imilarly, the different elements of the circular curve such as: T, L, LC, E, M, and the stationing of the PC and PT should be predetermined by calculations The computations should also include the deflection angles and chord lengths which will be needed when staking out the curve by half station intervals The accompanying sketch in the preceding page is given to serve as reference for the different abbreviations and terminologies used in this exercise 3 | ll values needed to lay out the curve should be tabulated accordingly efer to the accompanying sample format for the tabulation of required field data

TT

PT

DEFLECT LE (D,M,


CHD LETH (M


CU E DT

4 | et up and level the instrument at the designated vertex or point of intersection (P
5 | Establish on the ground the PC by laying out with a steel tape, the computed tangent distance (T
from the P The intersection angle (
at the P and the distance carried through the forward tangent will also be needed to set a stake at the PT 6 | Transfer and set up the instrument at the PC t the PC, lay off the total deflection angle from P to PT and check if the stake previously set up at the PT is along the line of sight f it doesn͛t check, an error exists in either measurement or computation s an added check, stake out the midpoint of the curve before beginning to set intermediate stations By bisecting the angle (O  
at the P and laying off the external distance (E
, the midpoint can be established  check of the deflection angle from the PC to the midpoint should equal to  4 7 | To establish the first curve station, first set the horizontal circle reading of the instrument to zero and sight along the back tangent Then turn the instrument about its vertical axis and lay off the required sub deflection angle and the corresponding chord distance for the first station et a hub to mark the located station

| ith the first station already established, now lay out the next chord length from it, and locate the second station on the intersection of the line of sight (defined by the next deflection angle
and the end of the chord lso set a hub to mark this located station 9 | epeat the process of locating succeeding stations on the curve by laying out the computed deflection angles and the chord distances from the previously established station Do this until all the required stations of the curve are laid out and properly marked on the ground O |hen the final station is established, the closing PT should be staked out using the final deflection angle and sub chord, to determine the disclosure in laying out the curve

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